GM Service Manual Online
For 1990-2009 cars only

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 P0119: Engine Coolant Temperature (ECT) Sensor Circuit Intermittent

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

ECT Sensor Signal

P0117

P0118, P0119

P0118, P0119*

P0119

Low Reference

--

P0118, P0119

P0118, P0119*

P0119

* 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°C to 142°C (-38° to 288°F) Varies with coolant temperature.

ECT Sensor Signal

143°C (289°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 volts to the ECT signal circuit and supplies a ground to the low reference circuit. The ECM monitors the performance of the ECT sensor. If the ECM detects excessive noise or rapid fluctuations in the ECT signal, this DTC sets.

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

P0119

    • DTC P0117, P0118, or P0128 is not set.
    • The ignition is ON or the engine is operating.
    • DTC P0119 runs continuously once the above conditions are met.

Conditions for Setting the DTC

P0119

The ECM detects that the ECT changed +/-4°C (+/-7°F) greater than the expected value during a calibrated amount of time.

Action Taken When the DTC Sets

DTC P0119 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P0119 is a Type B DTC.

Diagnostic Aids

The following table illustrates the ECM connector locations:

ECM Connector Location

X2

X1

Front of Vehicle

    • 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 stabilize after the thermostat opens.
    • High resistance in the circuits of either the ECT or IAT sensor could set a DTC.

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. Observe the scan tool engine coolant temperature (ECT) sensor parameter, while moving the ECT sensor connector and the engine control module (ECM) connector. The ECT sensor parameter should not fluctuate while moving the related harnesses and connectors.
  2. Repair the suspected harness or connection if the ECT parameter fluctuates greater than 3°C (5°F) while moving the related harnesses and connectors.
  3. Inspect the engine coolant level. Verify that the cooling system is operating correctly.
  4. If you suspect a condition with engine cooling system, refer to Symptoms - Engine Cooling.
  5. 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 List.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the engine coolant temperature (ECT) sensor.
  2. Remove the fuse that supplies B+ to circuit terminal X2-36 of the engine control module (ECM).
  3. Test for less than 5 ohms between the low reference circuit terminal 2 and ground.
  4. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  5. Install the fuse that supplies B+ to circuit terminal X2-36 of the ECM.
  6. Ignition ON, verify the scan tool ECT sensor parameter is at -40°C (-40°F).
  7. If greater than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

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

  8. Ignition ON, connect a 3A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool ECT sensor parameter is greater than 142°C (288°F).
  9. If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  10. If all circuits test normal, test or replace the ECT sensor.

Component Testing

  1. Ignition OFF, disconnect the harness connector of the engine coolant temperature (ECT) sensor.
  2. Important: 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 percent of the specification.
  4. If not within the specified range, replace the ECT sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Engine Coolant Temperature Sensor Replacement
    •  Control Module References for engine control module replacement, setup, and programming