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DTC P0137, P0138, or P0140

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    • Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0137 00: HO2S Circuit Low Voltage Sensor 2

DTC P0138 00: HO2S Circuit High Voltage Sensor 2

DTC P0140 00: HO2S Circuit Insufficient Activity Sensor 2

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Heater Voltage Supply

Opens fuse

P0037 00, P0141 00

-

P0141 00

Heater Low Control

P0037 00,

P0037 00, P0141 00

P0138 00, P0141 00

P0141 00

Signal Circuit High

P0137 00

-

P0138 00

-

Ground

-

-

-

-

Circuit/System Description

The heated oxygen sensors 1 or 2 are used for fuel control and catalyst monitoring. Each heated oxygen sensor compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an open loop mode, ignoring the heated oxygen sensor signal voltage while calculating the air to fuel ratio. The control module supplies the heated oxygen sensor with a reference, or bias voltage of about 450 mV. While the engine runs, each heated oxygen sensor heats up and begins to generate a voltage within a range of 0-1 000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient heated oxygen sensors 1 or 2 voltage fluctuation is observed by the control module, closed loop is entered. The control module uses the heated oxygen sensor voltage to determine the air to fuel ratio. An heated oxygen sensor voltage that increases above bias voltage toward 1 000 mV indicates a rich fuel mixture. A heated oxygen sensor voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements inside each heated oxygen sensor heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter closed loop earlier and the control module to calculate the air to fuel ratio sooner.

Conditions for Running the DTC
    • DTCs P0031 00, P0032 00, P0037 00, P0038 00, P0106 00, P0107 00, P0108 00, P0112 00, P0113 00, P0117 00, P0118 00, P0122 00, P0123 00, P0135 00, P0141 00, P0171 00, P0172 00, P0261 00, P0262 00, P0264 00, P0265 00, P0267 00, P0268 00, P0260 00, P0271 00, P0300 00, P0335 00, P0336 00, P0351 00, P0352 00, P0401 00, P0402 00, P0404 00, P0405 00, P0406 00, P0458 00, P0459 00, P0502 00,P0506 00, P0507 00, P0562 00, P0563 00, or P2110 00 are not set.
    • The engine has been operating for greater than 60 s.
    • The calculated airflow into the engine is greater than 2 g/s.
    • The engine coolant temperature is greater than 60°C (140°F).
    • The ignition voltage is between 11-18 V
    • The fuel system is in closed loop.
    • The vehicle is not decelerating.
    • The DTCs run continuously when the above conditions are met for 3 s.

Conditions for Setting the DTC

P0137 00

    • The ECM detects that the heated oxygen sensor 2 voltage parameter is less than 50 mV.
    • DTC P013 007 sets within 0.5 s during the lean test when the above condition is met for 30 s.

P0138 00

    • The ECM detects that the heated oxygen sensor 2 voltage parameter is greater than 950 mV.
    • DTC P0138 00 sets within 0.1 s during the rich test when the above condition is met for 5.5 s.

P0140 00

    • The ECM detects that the heated oxygen sensor (HO2S) 2 voltage is between 299 and 600 mV.
    • DTC P0140 00 sets within 4 s when the above condition is met for 60 s.

Action Taken When the DTC Sets

DTCs P0137 00, P0138 00 or P0140 00 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0137 00, P0138 00 or P0140 00 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs
    •  Heated Oxygen Sensor Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Clear the DTCs with a scan tool.
  2. Engine running, observe the scan tool HO2S 2 voltage parameter. The reading should fluctuate above and below the range of 350-550 mV.
  3. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that are captured in the freeze frame/failure records data.

Circuit/System Testing

Note: All modules must be powered down or misdiagnosis may result.

  1. Ignition OFF, disconnect the scan tool and wait 60 s to ensure all modules are powered down.
  2. Ignition OFF, disconnect the harness connector at the B52B Heated Oxygen Sensor 2.
  3. Ignition OFF, measure for less than 5 Ω between the B52B Heated Oxygen Sensor 2 low signal circuit terminal 3 and ground.
    4. ⇒If more than the specified range, test the B52B Heated Oxygen Sensor 2 low signal circuit for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
  4. Ignition ON, verify the scan tool HO2S Sensor 2 parameter is approximately 450 mV.
    5. ⇒If more than the specified value, test the B52B Heated Oxygen Sensor 2 high signal circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
    ⇒If less than the specified value, test the B52B Heated Oxygen Sensor 2 high signal circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.
  5. Ignition ON, install a 3 A fused jumper wire at the B52B Heated Oxygen Sensor 2 high signal circuit terminal 1. Toggle the other end of the jumper wire between the B52B Heated Oxygen Sensor 2 low signal circuit terminal 3 and battery voltage. Verify the scan tool HO2S Sensor 2 parameter toggles between 0 mV and approximately 1 000 mV.
    6. ⇒If the scan tool HO2S Sensor 2 parameter does not toggle correctly, test the B52B Heated Oxygen Sensor 2 high signal circuit for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
  6. Verify none of the following conditions exist:
    7. • Water intrusion in the HO2S harness connector
    • Low or high fuel system pressure--Refer to Fuel System Diagnosis and Fuel Injector Diagnosis
    • Fuel that is contaminated--Refer to Alcohol/Contaminants-in-Fuel Diagnosis
    • Fuel saturation of the evaporative emission (EVAP) canister
    • Exhaust leaks near the HO2S
    • Engine vacuum leaks
         ⇒If you find any of the above conditions, repair as necessary.
  7. If all circuits test normal, test or replace the B52B Heated Oxygen Sensor 2.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Heated Oxygen Sensor Replacement - Sensor 2
    • Control Module References for ECM replacement, setup, and programming
   


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