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DTC P0117 or P0118 - LF1 or LFW

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 P0117:  Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage

DTC P0118:  Engine Coolant Temperature (ECT) Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

ECT Sensor Signal

P0117

P0118

P0118*

P0116

Low Reference

-

P0118

P0118*

P0116

* Sensor or ECM damage may occur if the circuit is shorted to B+

Typical Scan Tool Data

ECT Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine operating in Closed Loop.

Parameter Normal Range: -39 to 142°C (-38 to 288°F) Varies with coolant temperature.

ECT Sensor Signal

150°C (302°F)

-40°C (-40°F)

-40°C (-40°F)*

Low Reference

-

-40°C (-40°F)

-40°C (-40°F)*

* Internal ECM or ECT sensor damage may occur if the circuit is shorted to B+

Circuit Description

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5 V to the ECT signal circuit and supplies an ground to the low reference circuit.

The following table illustrates the difference between temperature, resistance, and voltage:

ECT

ECT Resistance

ECT Signal Voltage

Cold

High

High

Warm

Low

Low

Conditions for Running the DTC

P0117

    • The engine is operating.
    • The start up intake air temperature (IAT) is less than 72°C (161°F).

OR

    • The start up intake air temperature (IAT) is greater than 72°C (161°F).
    •  The engine run time is greater than 59 s.
    • The DTC runs continuously once the above conditions are met.

P0118

    • The ignition is ON or the engine is operating.
    • The DTC runs continuously once the above condition is met.

Conditions for Setting the DTC

P0117

The ECM detects that the ECT is greater than 140°C (284°F) for greater than 1 s or a cumulative of 10 s.

P0118

The ECM detects that the ECT is less than -39°C (-38°F) for greater than 1 s or a cumulative of 10 s.

Action Taken When the DTC Sets

DTC P0117 and P0118 are Type B DTCs.

The ECM may activate the Cooling Fans at high speed.

Conditions for Clearing the MIL/DTC

DTC P0117 and P0118 are Type B DTCs.

Diagnostic Aids

    • Test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a DTC or a driveability condition. Refer to Temperature Versus Resistance - Engine Coolant Temperature Sensor .
    • If the vehicle has sat overnight, the IAT sensor and the ECT sensor values should display within 3°C (5°F).
    • After starting a cold engine, the ECT sensor temperature should rise steadily, then stabilise after the thermostat opens.
    • High resistance in the circuits of either the ECT or IAT sensor could set a DTC.
    • DTC's must be cleared before Engine Cooling Fan's are Commanded Off.

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Engine idling for 1 min. Observe the DTC information with a scan tool. DTCs P0117 and P0118 should not set.
  2. 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 you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the B34 ECT sensor.
  2. Caution: 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.

    Note: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage.

  3. Ignition Off all vehicle systems Off, this may take up to 2 minutes.Test for less than 5Ω between the low reference circuit terminal A and ground.
  4. If greater than the specified range, test the low reference circuit for an open/high resistance, or for a short to voltage. If the circuit tests normal, replace the K20 ECM.
  5. Ignition ON, verify that the scan tool ECT sensor parameter is at -40°C (-40°F).
  6. If greater than the specified value, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the K20 ECM.

    Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.

  7. Ignition ON, install a 3 A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the ECT sensor parameter is greater than 142°C (288°F).
  8. If less than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
  9. If all circuits test normal, test or replace the B34 ECT sensor.

Component Testing

  1. Ignition OFF, disconnect the harness connector at the B34 engine coolant temperature (ECT) sensor.
  2. Note: A thermometer can be used to test the sensor off the vehicle.

  3. Test the ECT sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Temperature Versus Resistance - Engine Coolant Temperature Sensor table and verify that the resistance is within 5 % of the specification.
  4. If not within the specified range, replace the B34 ECT sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Engine Coolant Temperature Sensor Replacement : LF1 or LFW
    • Control Module References for ECM replacement, setup, and programming
   


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