Diagnostic Trouble Code (DTC) P0335, P0336, P0337 or P0338
DTC Descriptor
DTC P0335 : Crankshaft Position (CKP) Sensor Circuit
DTC P0336 : Crankshaft Position (CKP) Sensor Performance
DTC P0337 :Crankshaft Position (CKP) Sensor Circuit Low Duty Cycle
DTC P0338 : Crankshaft Position (CKP) Sensor Circuit High Duty Cycle
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
CKP Sensor Signal | P0335 | P0335 | P0335 | P0336 |
Low Reference | - | P0335 | P0335, P0338 | P0336 |
Shielded Ground | - | - | - | P0336 |
Circuit/System Description
The crankshaft position (CKP) sensor is located on the rear of bank 1 of the engine block. The CKP sensor produces an AC voltage of different amplitude and frequency depending on the velocity of the crankshaft. The CKP sensor works in conjunction with a 58X reluctor wheel that is attached to the crankshaft. Each tooth on the reluctor wheel are spaced 6 degrees apart with one span having a 12 degree space. The engine control module (ECM) uses the 12 degree space to determine top dead center (TDC) for cylinders 1 and 4. The ECM determines when cylinder 1 is on the compression stroke by monitoring the CKP sensor and the camshaft position (CMP) sensors. The ECM can synchronize the ignition timing, fuel injector timing, and spark knock control based on the CKP sensor and the CMP sensor inputs. If the ECM loses the reference position to TDC, or the CKP signal is lost or erratic, one of these DTCs sets.
Conditions for Running the DTC
- The engine is cranking or operating.
- The ECM has detected more than 12 camshaft revolutions.
- The DTCs run continuously once the above conditions are met.
Conditions for Setting the DTC
P0335
The ECM does not detect a signal from the CKP sensor. OR, the ECM detects a CKP signal with out reference pulse for more than 3 revolutions. Either condition exists for more than 4 seconds.
P0336
The ECM re-syncs the engine position 6 or more times during an ignition cycle. OR, the ECM detects 14 or more interruptions in the engine speed signal during an ignition cycle. Either condition exists for more than 4 seconds.
P0337
The ECM detects a difference of more than 8 teeth between reference gap position pulses for 4 consecutive crankshaft revolutions in which the same number of pulses are detected each crankshaft revolution.
P0338
The ECM detects a difference of more than 8 teeth between reference gap position pulses for 4 consecutive crankshaft revolutions in which the same number of pulses are detected each crankshaft revolution.
Action Taken When the DTC Sets
DTCs P0335, P0336, P0337 and P0338 are Type A DTCs.
Conditions for Clearing the DTC
DTCs P0335, P0336, P0337 and P0338 are Type A DTCs.
Diagnostic Aids
The following conditions could also set the DTCs :
- Physical damage to the CKP sensor or the reluctor wheel.
- Excessive play or looseness of the CKP sensor or the reluctor wheel.
- Improper installation of the CKP sensor or the reluctor wheel.
- Foreign material passing between the CKP sensor and the reluctor wheel.
- Excessive air gap between the CKP sensor and the reluctor wheel.
- The ECM uses the camshaft position sensors to determine engine speed and position when there is a CKP sensor condition.
- The engine will operate with a CKP sensor condition only if the ECM has stored the learned reference position of the camshafts in memory. With a crankshaft position sensor condition the engine will go into a limp home mode after a hard restart. The ECM then calculates engine speed from one of the camshaft position sensors. During a limp home mode the following additional DTCs may set and should be ignored :
- DTC P0324 Knock Sensor (KS) Module Performance.
- DTC P1011 Intake Camshaft Position Actuator Park Position Bank 1.
- An intermittent condition in the camshaft position (CMP) sensor circuits can cause a CKP DTC to set. Inspect the CMP sensor, harness connections, and related wiring, if you suspect this condition.
Circuit/System Verification
- Ignition ON, clear the DTC Info with a scan tool. Attempt to start the engine, observe the DTC information with a scan tool. DTC P0335, P0336, and P0338 should not set.
- Move related harnesses/connectors of the CKP sensor and verify the engine does not stumble, stall, or change engine speed.
- If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.
Circuit/System Testing
Important : If the CKP sensor lead is damaged in any way, replace the CKP sensor.
- Ignition OFF, disconnect the harness connector at the crankshaft position (CKP) sensor.
- Ignition ON, verify that 2.0-3.0 volts is available on the signal circuit and the low reference circuit of the CKP sensor.
- If less than 2.0 volts, test the applicable circuit for a short to ground or an open/high resistance. If the circuits/connections test normal, replace the ECM.
- If more than 3.0 volts, test the applicable circuit for a short to voltage. If the circuits/connections test normal, replace the ECM.
- Ignition OFF, measure for 5 ohms or less between the ground shield circuit at the CKP sensor connector and ground.
- If more than 5 ohms, repair the open/high resistance in the shield circuit of the CKP sensor.
- Disconnect the ECM connectors, measure for continuity between the following circuits :
- The CKP signal circuit and the CKP low reference circuit.
- The CKP signal circuit and the ground shield circuit.
- The low reference circuit and the ground shield circuit.
- The DMM should display OL between all circuits.
- If continuity exists between any of the circuits, repair the wire to wire short between those circuits.
- If all circuits/connections test normal, test or replace the CKP sensor.
Component Testing
- Ignition OFF, disconnect the harness connector at the crankshaft position (CKP) sensor.
Important : If the CKP sensor lead is damaged in any way, replace the CKP sensor.
- Connect a DMM between the signal circuit and the low reference circuit of the CKP sensor.
- Test for 700-1200 ohms between the signal circuit and low reference circuit.
- If the resistance is not within the specified range, replace the CKP sensor.
- Set the DMM to the AC voltage scale.
- Test for 700-1200 ohms between the signal circuit and low reference circuit.
- If less than 1.4 ACV, replace the CKP sensor.
Diagnostic Trouble Code (DTC) P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, or P0393
DTC Descriptor
DTC P0341 : Intake Camshaft Position (CMP) Sensor Performance Bank 1
DTC P0342 : Intake Camshaft Position (CMP) Sensor Circuit Low Voltage Bank 1
DTC P0343 : Intake Camshaft Position (CMP) Sensor Circuit High Voltage Bank 1
DTC P0346 : Intake Camshaft Position (CMP) Sensor Performance Bank 2
DTC P0347 : Intake Camshaft Position (CMP) Sensor Circuit Low Voltage Bank 2
DTC P0348 : Intake Camshaft Position (CMP) Sensor Circuit High Voltage Bank 2
DTC P0366 : Exhaust Camshaft Position (CMP) Sensor Performance Bank 1
DTC P0367 : Exhaust Camshaft Position (CMP) Sensor Circuit Low Voltage Bank 1
DTC P0368 : Exhaust Camshaft Position (CMP) Sensor Circuit High Voltage Bank 1
DTC P0391 : Exhaust Camshaft Position (CMP) Sensor Performance Bank 2
DTC P0392 : Exhaust Camshaft Position (CMP) Sensor Circuit Low Voltage Bank 2
DTC P0393 : Exhaust Camshaft Position (CMP) Sensor Circuit High Voltage Bank 2
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
CMP Sensor 5 Volt Reference | P0343, P0348, P0368, P0393 | P0343, P0348, P0368, P0393 | - | P0341, P0346, P0366, P0391 |
CMP Sensor Signal Intake Bank 1 | P0342 | P0343 | P0343 | P0341 |
CMP Sensor Signal Intake Bank 2 | P0347 | P0348 | P0348 | P0346 |
CMP Sensor Signal Exhaust Bank 1 | P0367 | P0368 | P0368 | P0366 |
CMP Sensor Signal Exhaust Bank 2 | P0392 | P0393 | P0393 | P0391 |
Low Reference | - | P0343, P0348, P0368, P0393 | - | P0341, P0346, P0366, P0391 |
Circuit/System Description
Each camshaft is equipped with a camshaft position (CMP) sensor that the engine control module (ECM) monitors. The CMP sensor is a hall effect switch that works in conjunction with a 4X reluctor wheel. The reluctor wheels are mounted to the camshaft position actuators that are mounted to the end of the camshafts. The ECM uses the CMP sensor signals in order to determine the position of the camshafts. The ECM supplies 5 volts to the CMP sensors on the 5-volt reference circuits, and supplies a ground on the low reference circuits. The CMP sensors provide a signal to the ECM on the signal circuits. If the ECM detects extra or missing CMP sensor signal transitions, or a signal voltage that is more or less than the predetermined range, within a certain number of crankshaft revolutions, one of these DTCs sets.
Conditions for Running the DTC
- The engine is operating for more than 1 second.
- The DTCs run continuously once the above condition is met.
Conditions for Setting the DTC
DTC P0341, P0346, P0366, P0391
The CMP sensor signal voltage is always high and the ECM detects no pulses from the CMP sensor for more than 4 seconds.
DTC P0342, P0347, P0367, P0392
The CMP sensor signal voltage is always low and the ECM detects no pulses from the CMP sensor for more than 4 seconds.
DTC P0343, P0348, P0368, P0393
The CMP sensor signal voltage is always high and the ECM detects no pulses from the CMP sensor for more than 4 seconds.
Action Taken When the DTC Sets
DTCs P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, and P0393 are Type E DTCs.
Conditions for Clearing the DTC
DTCs P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, and P0393 are Type E DTCs.
Diagnostic Aids
The following conditions can also set the DTC :
- Physical damage to the CMP sensor or the reluctor wheel.
- Incorrect play or looseness of the CMP sensor or the reluctor wheel.
- Incorrect installation of the CMP sensor or the reluctor wheel.
- Foreign material passing between the CMP sensor and the reluctor wheel.
- Incorrect air gap between the CMP sensor and the reluctor wheel.
Circuit/System Verification
Engine idling, observe the DTC information with a scan tool. DTCs P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, and P0393 should not set.
Circuit/System Testing
- Ignition OFF, remove the ECM Fuse/relay that supplies B+ to terminal of the ECM.
- Disconnect the harness connector at the appropriate CMP sensor.
Notice : Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.
Important : The control module or the sensor may be damaged if the circuit is shorted to B+ voltage.
- Test for 5 ohms or less between the low reference circuit and a known ground.
- If greater than 5 ohms, test the low reference circuit for an open/high resistance or for a short to voltage. If the circuit/connections test normal, replace the ECM.
- Install the ECM Fuse that supplies B+ to the ECM.
- Ignition ON, measure for 4.8-5.2 volts between the 5 volt reference circuit of the CMP sensor and a known ground.
- If less than 4.8 volts, test the 5 volt reference circuit for a short to ground or an open/high resistance. If the circuits/connections test normal, replace the ECM.
- If more than 5.2 volts, test the 5 volt reference circuit for a short to voltage. If the circuits/connections test normal, replace the ECM.
- Measure for 4.8-5.2 volts between the signal circuit of the CMP sensor and a known ground with a DMM.
- If the voltage is greater than 5.2 volts, test for a short to voltage in the signal circuit of the CMP sensor. If circuit/connections test normal, replace the ECM.
- If the voltage is less than 4.8 volts, test for a short to ground or an open/high resistance in the signal circuit of the CMP sensor. If circuit/connections test normal, replace the ECM.
- If all circuits/connections test normal, replace the CMP sensor.
Diagnostic Trouble Code (DTC) P0350
DTC Descriptor
DTC P0350 :Ignition Coil Control Circuit
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit/System Description
The ignition system on this engine uses individual ignition coils and ignition control (IC) circuits for each cylinder. Ignition 1 voltage is supplied to each bank of ignition coils. The engine control module (ECM) controls the ignition system operation. The ECM controls each coil using the IC circuits. The ECM commands the IC circuit low when a spark event is requested.
The sequencing and timing are ECM controlled.
Conditions for Running the DTC
- The engine is operating.
- The ignition 1 voltage is between 10.5-18 volts.
- The engine speed is between 1,400-5,000 RPM.
- The DTCs run continuously once the above condition is met for more than 1 second.
Conditions for Setting the DTC
DTC P0350
The ECM detects the ignition control circuit has Short to ground or open/high resistance.
Action Taken When the DTC Sets
DTC P0350 is a type E DTC.
Conditions for Clearing the DTC
DTC P0350 is a type E DTC.
Circuit/System Verification
Operate the engine above 1400 RPM for 15 seconds, observe the DTC information with a scan tool. DTCs P0350 should not set.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the appropriate ignition coil.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal and a known ground.
- If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test the ICcircuit terminal for a short to ground.
- Set the DMM to the AC Hertz scale for this test.
- Crank or start the engine, test for more than 3 Hz between the appropriate ignition control circuit and a known ground.
- If less than 3 Hz, test the ignition control circuit for a short to voltage, short to ground or an open/high resistance. If the circuit/connection test normal, replace the ECM.
- Measure for 5 ohms or less between both ground circuits of the ignition coil connector and the ECM housing.
- If greater than 5 ohms, test for an open/high resistance in the ground circuits. If the circuit/connections test normal, replace the ECM.
- If all circuits/connections test normal, replace the ignition coil.
Diagnostic Trouble Code (DTC) P0351, P0352, P0353, P0354, P0355, P0356, P2300, P2301, P2303, P2304, P2306, P2307, P2309, P2310, P2312, P2313, P2315, or P2316
DTC Descriptor
DTC P0351 : Ignition Coil 1 Control Circuit
DTC P0352 : Ignition Coil 2 Control Circuit
DTC P0353 : Ignition Coil 3 Control Circuit
DTC P0354 : Ignition Coil 4 Control Circuit
DTC P0355 : Ignition Coil 5 Control Circuit
DTC P0356 : Ignition Coil 6 Control Circuit
DTC P2300 : Ignition Coil 1 Control Circuit Low Voltage
DTC P2301 : Ignition Coil 1 Control Circuit High Voltage
DTC P2303 : Ignition Coil 2 Control Circuit Low Voltage
DTC P2304 : Ignition Coil 2 Control Circuit High Voltage
DTC P2306 : Ignition Coil 3 Control Circuit Low Voltage
DTC P2307 : Ignition Coil 3 Control Circuit High Voltage
DTC P2309 : Ignition Coil 4 Control Circuit Low Voltage
DTC P2310 : Ignition Coil 4 Control Circuit High Voltage
DTC P2312 : Ignition Coil 5 Control Circuit Low Voltage
DTC P2313 : Ignition Coil 5 Control Circuit High Voltage
DTC P2315 : Ignition Coil 6 Control Circuit Low Voltage
DTC P2316 : Ignition Coil 6 Control Circuit High Voltage
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
Ignition 1 Voltage | P0261, P0264, P0267, P0270, P0273, P0276, P0300-P0306 | P0300-P0306 | - | P0300-P0306 |
Ignition Coil 1 Control Circuit | P2300 | P0351 | P2301 | P0300, P0301 |
Ignition Coil 2 Control Circuit | P2303 | P0352 | P2304 | P0300, P0302 |
Ignition Coil 3 Control Circuit | P2306 | P0353 | P2307 | P0300, P0303 |
Ignition Coil 4 Control Circuit | P2309 | P0354 | P2310 | P0300, P0304 |
Ignition Coil 5 Control Circuit | P2312 | P0355 | P2313 | P0300, P0305 |
Ignition Coil 6 Control Circuit | P2315 | P0356 | P2316 | P0300, P0306 |
Circuit/System Description
The ignition system on this engine uses individual ignition coils and ignition control (IC) circuits for each cylinder. Ignition 1 voltage is supplied to each bank of ignition coils. The engine control module (ECM) controls the ignition system operation. The ECM controls each coil using the IC circuits. The ECM commands the IC circuit low when a spark event is requested.
The sequencing and timing are ECM controlled.
Conditions for Running the DTC
- The engine is operating.
- The ignition 1 voltage is between 10.5-18 volts.
- The engine speed is between 1,400-5,000 RPM.
- The DTCs run continuously once the above condition is met for more than 1 second.
Conditions for Setting the DTC
DTC P0351, P0352, P0353, P0354, P0355, or P0356
The ECM detects the ignition control circuit is open.
DTC P2300, P2303, P2306, P2309, P2312, or P2315
The ECM detects the ignition control circuit is shorted to ground.
DTC P2301, P2304, P2307, P2310, P2313, or P2316
The ECM detects the ignition control circuit is shorted to voltage.
Action Taken When the DTC Sets
DTCs P0351, P0352, P0353 P0354, P0355, P0356, P2300, P2301, P2303, P2304, P2306, P2307, P2309, P2310, P2312, P2313, P2315, and P2316 are Type E DTCs.
Conditions for Clearing the DTC
DTCs P0351, P0352, P0353 P0354, P0355, P0356, P2300, P2301, P2303, P2304, P2306, P2307, P2309, P2310, P2312, P2313, P2315, and P2316 are Type E DTCs.
Diagnostic Aids
Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits, may cause this DTC to set.
Circuit/System Verification
Operate the engine above 1400 RPM for 15 seconds, observe the DTC information with a scan tool. DTCs P0351, P0352, P0353 P0354, P0355, P0356, P2300, P2301, P2303, P2304, P2306, P2307, P2309, P2310, P2312, P2313, P2315, and P2316 should not set.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the appropriate ignition coil.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal and ground.
- If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test the IC circuit terminal for a short to ground.
- Set the DMM to the AC Hertz scale for this test.
- Crank or start the engine, test for more than 3 Hz between the appropriate ignition control circuit and ground.
- If less than 3 Hz, test the ignition control circuit for a short to voltage, short to ground or an open/high resistance. If the circuit/connection test normal, replace the ECM.
- Measure for 5 ohms or less between both ground circuits of the ignition coil connector and the ECM housing.
- If greater than 5 ohms, test for an open, or high resistance in the ground circuits. If the circuit/connections test normal, replace the ECM.
- If all circuits/connections test normal, replace the ignition coil.
Diagnostic Trouble Code (DTC) P0420 or P0430
DTC Descriptor
DTC P0420 : Catalyst System Low Efficiency Bank 1
DTC P0430 : Catalyst System Low Efficiency Bank 2
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit/System Description
In order to maintain a reasonably low emission level of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) a 3-way catalytic converter (TWC) is used. The catalyst within the converter promotes a chemical reaction that oxidizes the HC and CO present in the exhaust gas. This reaction converts the gases into harmless water vapor and carbon dioxide. The catalyst also reduces the NOx, converting the NOx into nitrogen. The engine control module (ECM) monitors this process using the post catalyst heated oxygen sensor (HO2S) signal. The post-catalyst HO2S located in the exhaust stream after the TWC, produces an output signal that indicates the oxygen storage capacity of the catalyst. The oxygen storage capacity (OSC) determines the ability of the catalyst to convert the exhaust emissions effectively. If the catalyst is functioning correctly, the post-catalyst HO2S signal will be far less active than the signal produced by the pre-catalyst HO2S.
To determine OSC, the ECM commands a rich air/fuel mixture until all oxygen is removed from the catalyst.
The ECM then commands a lean air/fuel mixture and monitors the rear heated oxygen sensors to calculate the oxygen storage capacity. The catalyst is operated in this mode until one of the following conditions occur :
- The oxygen stored in the catalyst exceeds a calibrated threshold, which is determined from the rear HO2S signal.
- The rear HO2S indicates the catalyst to be completely saturated with oxygen, which is determined from the rear HO2S signal.
Conditions for Running the DTC
- Before the ECM can report DTC P0420 or P0430 failed, DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0053, P0056, P0057, P0058, P0059, P0101, P0102, P0103, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0150, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0335, P0336, P0338, P167A, P167B, P2096, P2097, P2098, P2099, P2195, P2196, P2197, P2198, P2232, P2235, P2237, P2240, P2243, P2247, P2251, P2254, P2270, P2271, P2272, P2273, P2297, P2298, P2626, and P2629 must run and pass.
- DTCs P0010, P0011, P0013, P0014, P0020, P0021, P0023, P0024, P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0053, P0056, P0057, P0058, P0059, P0101, P0102, P0103, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0125, P0130, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0150, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0300, P0301-P0306, P0443, P0458, P0459, P0496, P167A, P167B, P2088, P2089, P2090, P2091, P2092, P2093, P2094, P2095, P2096, P2097, P2098, P2099, P2100, P2101, P2107, P2119, P2122, P2123, P2127, P2128, P2138, P2176, P2177, P2178, P2179, P2180, P2187, P2188, P2189, P2190, P2195, P2196, P2197, P2198, P2232, P2235, P2237, P2240, P2243, P2247, P2251, P2254, P2270, P2271, P2272, P2273, P2297, P2298, P2626, and P2629 are not set.
- The engine speed is 1040-3000 RPM.
- The air flow into the engine is between 7-16 g/s and not changing more than 3 g/s.
- The engine intake air temperature (IAT) at engine start-up is more than -30°C (-22°F).
- The engine is operating for more than 7 minutes.
- The engine is operating in Closed Loop.
- The calculated TWC temperature is between 500-750°C (932-1,382°F) and steady.
- The above conditions exist for approximately 17 minutes.
- DTCs P0420 and P0430 run once a drive cycle. The ECM will attempt to run this diagnostic up to 3 times a drive cycle.
Conditions for Setting the DTC
The ECM determines that the efficiency of the catalyst has degraded below a calibrated threshold for more than 4 seconds.
Action Taken When the DTC Sets
DTCs P0420 and P0430 are Type E DTCs.
Conditions for Clearing the DTC
DTCs P0420 and P0430 are Type E DTCs.
Diagnostic Aids
Inspect for the following conditions, which may cause a catalytic converter to degrade :
- An engine misfire
- High engine oil or high coolant consumption
- Retarded spark timing
- A weak or poor spark
- A lean fuel mixture
- A rich fuel mixture
- A damaged oxygen sensor or wiring harness
Circuit/System Testing
- Verify there are no HO2S or misfire DTCs set.
- If there is an HO2S or misfire DTC set, refer to the appropriate DTC information to diagnosis the applicable DTC, before proceeding with this diagnostic procedure.
- Verify the following conditions do not exist with the appropriate catalytic converter:
- Dents
- A severe discoloration caused by excessive temperatures
- Road damage
- An internal rattle caused by damaged catalystsubstrate
- Restrictions
- If a condition is found, replace the appropriate catalytic converter.
- Verify the following conditions do not exist with the exhaust system :
- Leaks
- Physical damage
- Loose or missing hardware
- Properly torqued HO2S
- If a condition is found, repair the exhaust system.
- Verify the following conditions do not exist with the appropriate HO2S 2 :
- A grounded wiring harness
- Damage
- If a condition is found, replace the appropriate HO2S 2.
- If no physical condition is detected and the HO2S 2 is as active as the HO2S 1 after operating the engine at 1,500 RPM for 1 minute and then returning to a stabilized idle, then replace the catalytic converter.
Diagnostic Trouble Code (DTC) P0443, P0458, or P0459
DTC Descriptor
DTC P0443 : Evaporative Emission (EVAP) Purge Solenoid Control Circuit
DTC P0458 : Evaporative Emission (EVAP) Purge Solenoid Control Circuit Open
DTC P0459 : Evaporative Emission (EVAP) Purge Solenoid Control Circuit Shorted
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
Ignition 1 Voltage | P0458 | P0443 | - | - |
EVAP Canister Purge Valve Control Circuit | P0458 | P0443 | P0459 | - |
Circuit/System Description
The evaporative emission (EVAP) canister purge valve is used to purge fuel vapor from the EVAP canister to the intake manifold. The EVAP canister purge valve is pulse width modulated (PWM). Ignition voltage is supplied directly to the EVAP canister purge valve. The engine control module (ECM) controls the solenoid by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is within a predetermined range when the circuit is commanded OFF, this DTC sets.
Conditions for Running the DTC
- The ignition is ON or the engine is operating.
- The engine speed is more than 80 RPM.
- The ignition 1 voltage is between 10.5-18 volts.
- The ECM has commanded the EVAP canister purge valve ON and OFF at least once during the ignition cycle.
- The DTCs run continuously once the above conditions are met.
Conditions for Setting the DTC
P0443
The ECM detects the voltage on the EVAP canister purge valve control circuit is between 2.6-4.6 volts when the driver is commanded OFF. The condition exists for less than 4 second.
P0458
The ECM detects the EVAP purge solenoid control circuit is open.
P0459
The ECM detects the EVAP purge solenoid control circuit is shorted to ground or voltage.
Action Taken When the DTC Sets
DTC P0443, P0458 and P0459 are Type E DTCs.
Conditions for Clearing the DTC
DTC P0443, P0458 and P0459 are Type E DTCs.
Circuit/System Verification
- Ignition ON, command the EVAP purge solenoid ON and OFF with a scan tool. You should hear an audible click.
- If the vehicle passes the Circuit/System Verification, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.
Circuit/System Testing
- Ignition OFF, disconnect the EVAP purge solenoid harness connector at the EVAP purge solenoid.
- Ignition ON, verify that a test lamp illuminates between the ignition 1, voltage circuit and ground.
- If the test lamp does not illuminate, test the ignition 1, voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1, voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.
- Connect a test lamp between the control circuit terminal and the ignition 1, voltage circuit terminal.
- Command the EVAP purge solenoid ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
- If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, test or replace the EVAP purge solenoid.
Component Testing
- Ignition OFF, disconnect the harness connector at the EVAP purge solenoid.Test for24-28 ohms of resistance between the control circuit and the ignition 1, voltage circuit of the EVAP purge solenoid.
- If the resistance is not within the specified range, replace the EVAP purge solenoid.
- Test for infinite resistance between each terminal of the EVAP purge solenoid and the EVAP purge solenoid housing.
- If less than infinite resistance, replace the EVAP purge solenoid.
Diagnostic Trouble Code (DTC) P0451
DTC Descriptor
DTC P0451 : Fuel Tank Pressure (FTP) Sensor Performance
Circuit/System Description
The control module monitors the fuel tank pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the evaporative emission (EVAP) diagnostic test. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. This DTC sets if the engine control module (ECM) detects one of the following conditions :
- The FTP sensor signal voltage is not within a calibrated range on a cold start-up.
- The FTP sensor signal does not change by a calibrated amount when purge is active.
- The FTP sensor signal oscillates more than a calibrated amount when vehicle speed is less than 30 km/h (50 mph).
The following table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.
FTP Sensor Signal | Voltage Fuel Tank Pressure |
High, Approximately 1.5 Volts or More | Negative Pressure/Vacuum |
Low, Approximately 1.5 Volts or Less | Positive Pressure |
Conditions for Running the DTC
The ignition is on and the engine is running.
Conditions for Setting the DTC
- DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0119, P0125, P0449, P0498, P0506, P0507, P0721, P0722, P2227, P2228, and P2229 are not set.
- The fuel level is between 12-88 percent.
- The start-up engine coolant temperature (ECT) is less than 35°C (95°F).
- The vehicle speed is between 10-30 km/h (6-19 mph).
- The ECM is commanding purge.
- The ratio between ambient pressure and the calculated manifold pressure is less than 0.8.
- DTC P0451 runs continuously once the above conditions are met for approximately 100 seconds.
Action Taken When the DTC Sets
DTC P0451 is Type E DTC.
Conditions for Clearing the DTC
DTC P0451 is Type E DTC.
Diagnostic Aids
- A blocked or clogged EVAP canister vent may set this DTC.
- A large leak in the EVAP system could cause this DTC to set.
Circuit/System Testing
- Remove the fuel fill cap. Connect the GE-41415-50to the fuel tank filler neck. Connect the J 41413-200 to the J 41415-40.
- Seal the system using the Purge Seal function with a scan tool.
- Pressurize the EVAP system with nitrogen to 5 inches H20. Compare the Fuel Tank Pressure Sensor parameter with a scan tool to the J 41413-200 pressure/vacuum gage. The scan tool FTP sensor parameter should be within 1 inch H20 of the pressure/vacuum gage.
- If the FTP sensor parameter is not within 1 inch H20 of the pressure/vacuum gage, replace the FTP sensor.
- Command the vent solenoid valve OPEN with a scan tool.
- If the FTP sensor parameter is not 0 inch H20, replace the FTP sensor.
Diagnostic Trouble Code (DTC) P0452 or P0453
DTC Descriptor
DTC P0452 : Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage
DTC P0453 : Fuel Tank Pressure (FTP) Sensor Circuit High Voltage
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
5-Volt Reference | P0122, P0452 | P0452 | P0453 | - |
FTP Sensor Signal | P0452 | P0452 | P0452 | - |
Low Reference | - | - | - | - |
Circuit/System Description
The evaporative emission (EVAP) system is used to store fuel vapors in order to reduce the amount of fuel vapors into the atmosphere. The fuel tank pressure (FTP) sensor is only used for EVAP system diagnostics. The FTP sensor is a transducer that varies resistance according to changes in the fuel tank pressure. The engine control module (ECM) monitors the FTP sensor signal in order to detect vacuum decay and excess vacuum during the EVAP system diagnostic test. The ECM supplies a 5-volt reference and a low reference circuit to the FTP sensor.
FTP Sensor Signal Voltage | Fuel Tank Pressure |
High, Approximately 1.5 Volts or More | Negative Pressure/Vacuum |
Low, Approximately | Positive Pressure |
Conditions for Running the DTC
- The ignition is ON or the engine is operating.
- The DTCs run continuously once the above condition is met.
Conditions for Setting the DTC
DTC P0452
The ECM detects the FTP sensor signal voltage is less than 0.13 volts.
DTC P0453
The ECM detects the FTP sensor signal voltage is more than 4.6 volts.
Action Taken When the DTC Sets
DTC P0452 and P0453 are Type E DTCs.
Conditions for Clearing the DTC
DTC P0452 and P0453 are Type E DTCs.
Diagnostic Aids
If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.
Circuit/System Verification
- Ignition ON, observe the FTP Sensor voltage parameter. The FTP sensor voltage should be between 0.2–4.8 volts.
- If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the FTP sensor.
- Ignition OFF, test for less than 5.0 ohms of resistance between the low reference circuit and ground.
- If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replae the ECM.
Important : The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.
- Ignition ON, test for 4.8–5.2 volts between the 5-volt reference circuit and ground.
- If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit/connections test normal, replace the ECM.
- If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.
- Verify that the FTP Sensor parameter is less than 4.8 volts
- If greater than the specified value, test the signal circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.
- Ignition ON, install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit. Verify that the FTP Sensor parameter is greater than 4.8 volts.
- If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.
- If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.
Diagnostic Trouble Code (DTC) P0460
DTC Descriptor
DTC P0460 :Fuel Level Sensor Circuit
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
Fuel Level Sensor Reference Voltage Circuit | P0462 | - | - | P0461 |
Fuel Level Sensor Signal Circuit | P0462 | P0463 1 P0464 | P0463 | P0461 |
Fuel Level Sensor Low Reference Circuit | - | P0463 1 P0464 | P0463 | P0461 |
- Fuel gauge Inaccurate or Inoperative
|
Circuit/System Description
The fuel level sensor changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the fuel level sensor in order to determine the fuel level. When the fuel tank is full, the sensor resistance is low and the ECM senses a low signal voltage. When the fuel tank is empty, the sensor resistance is high and the ECM senses a high signal voltage. The ECM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via GMLAN serial data circuit to the instrument cluster in order to control the fuel gauge. The fuel information is also used for misfire and vaporative emission (EVAP) diagnostics.
Conditions for Running the DTC
- The ignition is ON, with the engine running.
- The system voltage is between 9-16 volts.
Conditions for Setting the DTC
- The sender output is less than 0.5 volts.
- The above condition is present for greater than 30 seconds.
Action Taken When the DTC Sets
DTC P0460 is a type E DTC.
Conditions for Clearing the DTC
DTC P0460 is a type E DTC.
Circuit/System Verification
Ignition ON, observe the scan tool Fuel Tank Level Remaining parameter. The reading should be between 4 percent and 98 percent.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the fuel level sensor.
- Ignition ON, verify that the scan tool fuel tank level remaining parameter is less than 4 percent.
- If greater than 4 percent, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
- If all circuits test normal, replace the fuel level sensor.
Diagnostic Trouble Code (DTC) P0461
DTC Descriptor
DTC P0461 :Fuel Level Sensor 1 Performance
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
Fuel Level Sensor Reference Voltage Circuit | P0462 | - | - | P0461 |
Fuel Level Sensor Signal Circuit | P0462 | P0463 1 P0464 | P0463 | P0461 |
Fuel Level Sensor Low Reference Circuit | - | P0463 1 P0464 | P0463 | P0461 |
- Fuel gauge Inaccurate or Inoperative
|
Circuit/System Description
The fuel level sensor changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the fuel level sensor in order to determine the fuel level. When the fuel tank is full, the sensor resistance is low and the ECM senses a low signal voltage. When the fuel tank is empty, the sensor resistance is high and the ECM senses a high signal voltage. The ECM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via GMLAN serial data circuit to the instrument cluster in order to control the fuel gauge. The fuel information is also used for misfire and evaporative emission (EVAP) diagnostics.
This diagnostic tests for a stuck fuel level sensor signal.
The ECM sets this DTC if the fuel level sensor signal appears to be stuck based on a lack of signal evariation expected during normal operation.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The ECM detects a change in fuel level less than 10 litres over a distance of 241.4 km.
Action Taken When the DTC Sets
DTC P0461 is a type E DTC.
Conditions for Clearing the DTC
DTC P0461 is a type E DTC.
Circuit/System Testing
- Ignition OFF, remove the fuel level sender and verify that there is no obstructions interfering with the fuel level sender.
- If interference is present, remove the obstruction.
- If no interference is present, replace the fuel level sender.
Diagnostic Trouble Code (DTC) P0462
DTC Descriptor
DTC P0462 :Fuel Level Sensor 1 Low Voltage
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
Fuel Level Sensor Reference Voltage Circuit | P0462 | - | - | P0461 |
Fuel Level Sensor Signal Circuit | P0462 | P0463 1 P0464 | P0463 | P0461 |
Fuel Level Sensor Low Reference Circuit | - | P0463 1 P0464 | P0463 | P0461 |
- Fuel gauge Inaccurate or Inoperative
|
Circuit/System Description
The fuel level sensor changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the fuel level sensor in order to determine the fuel level. When the fuel tank is full, the sensor resistance is low and the ECM senses a low signal voltage. When the fuel tank is empty, the sensor resistance is high and the ECM senses a high signal voltage. The ECM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via GMLAN serial data circuit to the instrument cluster in order to control the fuel gauge. The fuel information is also used for misfire and evaporative emission (EVAP) diagnostics.
Conditions for Running the DTC
- The ignition is ON, with the engine running.
- The system voltage is between 9-16 volts.
Conditions for Setting the DTC
- The sender output is less than 0.5 volts.
- The above condition is present for greater than 30 seconds.
Action Taken When the DTC Sets
DTC P0462 is a type E DTC.
Conditions for Clearing the DTC
DTC P0462 is a type E DTC.
Circuit/System Verification
Ignition ON, observe the scan tool Fuel Tank Level Remaining parameter. The reading should be between 4 percent and 98 percent.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the fuel level sensor.
- Ignition ON, verify that the scan tool fuel tank level remaining parameter is less than 4 percent.
- If greater than 4 percent, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
- If all circuits test normal, replace the fuel level sensor.
Diagnostic Trouble Code (DTC) P0463
DTC Descriptor
DTC P0463 :Fuel Level Sensor 1 High Voltage
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
Fuel Level Sensor Reference Voltage Circuit | P0462 | - | - | P0461 |
Fuel Level Sensor Signal Circuit | P0462 | P0463 1 P0464 | P0463 | P0461 |
Fuel Level Sensor Low Reference Circuit | - | P0463 1 P0464 | P0463 | P0461 |
- Fuel gauge Inaccurate or Inoperative
|
Circuit/System Description
The fuel level sensor changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the fuel level sensor in order to determine the fuel level. When the fuel tank is full, the sensor resistance is low and the ECM senses a low signal voltage. When the fuel tank is empty, the sensor resistance is high and the ECM senses a high signal voltage. The ECM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the tank. The ECM sends the fuel level percentage via GMLAN serial data circuit to the instrument cluster in order to control the fuel gauge. The fuel information is also used for misfire and evaporative emission (EVAP) diagnostics.
Conditions for Running the DTC
- The ignition is ON, with the engine running.
- The system voltage is between 9-16 volts.
Conditions for Setting the DTC
- The sensor output is greater than 3.5 volts.
- The above condition is present for greater than 30 seconds.
Action Taken When the DTC Sets
DTC P0463 is a type E DTC.
Conditions for Clearing the DTC
DTC P0463 is a type E DTC.
Circuit/System Verification
Ignition ON, observe the scan tool fuel tank level remaining parameter. The reading should be between 4 percent and 98 percent.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the fuel level sensor.
- Test for less than 1.0 ohm of resistance between the low reference circuit and a known ground.
- If greater than 1.0 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
- Ignition ON, install a 3A fusible link wire between the signal circuit and the low reference circuit. Verify the scan tool Fuel tank level remaining parameter is greater than 98 percent.
- If less than 98 percent, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, replace the fuel level sensor.
Diagnostic Trouble Code (DTC) P0480 or P0481
DTC Descriptor
DTC P0480 : Low Speed Cooling Fan Relay Control Circuit
DTC P0481 :High Speed Cooling Fan Relay Control Circuit
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
Low Speed Cooling Fan Relay Control Circuit | P0480 | P0480 | P0480 |
Low Speed Cooling Fan Relay Coil Voltage Supply Circuit | P0480 | P0480 | P0480 |
High Speed Cooling Fan Relay Control Circuit | P0481 | P0481 | P0481 |
High Speed Cooling Fan Relay Coil Voltage Supply Circuit | P0481 | P0481 | P0481 |
Circuit/System Description
The engine control module (ECM) grounds the cooling fan relay control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the ECM. When the ECM is commanding a component ON, the voltage potential of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the ECM detects that the actual state of the control circuit does not match the expected state, a DTC will set.
Conditions for Running the DTC
- The ignition is ON.
- The system voltage is between 9-18 volts.
Conditions for Setting the DTC
- An improper voltage level has been detected on the cooling fan relay control circuit.
- The condition must be present for a minimum of 30 seconds.
Action Taken When the DTC Sets
DTCs P0480 and P0481 are type B DTCs.
Conditions for Clearing the DTC
DTCs P0480 and P0481 are type B DTCs.
Circuit/System Verification
Ignition ON, command each relay ON and OFF with a scan tool. Feel or listen to verify that each relay turns ON and OFF with each command.
Circuit/System Testing
- Ignition OFF, disconnect the fan relay.
- Ignition ON, verify that a test lamp does not illuminate between the earth terminal and a known ground.
- If the test lamp illuminates, test the control circuit for a short to voltage.
- Ignition ON, Connect a test lamp between the control circuit terminal and a known ground. Command the relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the relay control circuit for a short to voltage. If the circuit tests normal replace the ECM.
- If the test lamp is always OFF, test the relay control circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the ECM.
- Connect a test lamp between the Battery+ terminal and a known ground.
- If the test lamp does not activate, test the Battery+ for a short to ground or an open/high resistance.
- Connect a 30A fusible link wire between the battery positive post and the fan voltage supply circuit terminal and verify fan activation.
- If the fan does not activate, test the fan voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fan.
- If all circuits test normal replace the affected relay.
Diagnostic Trouble Code (DTC) P0500
DTC Descriptor
DTC P0500 : Vehicle Speed Sensor (VSS) Circuit
Diagnostic Fault Information
Perform the Diagnostic System Check prior to using this diagnostic procedure.
Circuit/System Description
The vehicle speed sensor (VSS) provides vehicle speed information to the engine control module (ECM). The VSS is a permanent magnet generator. The VSS produces an AC voltage as rotor teeth on the output shaft of the transmission, FWD, or transfer case, AWD, pass through the sensor’s magnetic field. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The ECM converts the pulsing voltage to vehicle speed. The ECM uses the vehicle speed signal to determine shift timing and torque converter clutch (TCC) scheduling.
Conditions for Running the DTC
P0500
- No MAP sensor DTCs are set.
- No TP sensor DTCs are set.
- The engine vacuum is 0-105 kPa (0-15 psi).
- The engine torque is 54-542 N·m (40-400 lb-ft).
- The TP angle is greater than 12 percent.
- The engine speed is greater than 3,000 RPM.
- The transmission is not in PARK or NEUTRAL.
Conditions for Setting the DTC
P0500
The transmission output speed is less than 150 RPM for 3 seconds.
Action Taken When the DTC Sets
DTCs P0500 is a Type E DTC.
Conditions for Clearing the DTC
DTCs P0500 is a Type E DTC.
Circuit/System Verification
- Start the engine, operate the vehicle within the conditions for running the DTC, DTC P0500 should not set.
Circuit/System Testing
- Turn ON the ignition, with the engine OFF.
- Disconnect the VSS sensor.
- Connect a DMM between the power terminal of the VSS harness connector and a known ground.
- If the voltage is less than 4.9 volts, test the VSS power circuit for a short to ground or an open/high resistance.
- If the voltage is greater than 5.2 volts, test the VSS power circuit for a short to voltage.
- If the VSS circuit tests normal and the voltage is not within the proper range then replace the ECM.
- Connect a 3A fusible link wire between the signal circuit of the VSS and the low reference circuit.
- Observe the sensor parameters while connecting and disconnecting the link between the VSS sensor signal and the low reference circuit.
- The VSS should switch between the upper and lower limits.
- If the VSS signal does not switch between the upper and lower limits then replace the ECM.
- If the VSS signal does switch between the upper and lower limits then replace the VSS.
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