For 1990-2009 cars

### 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 provide an overview of each diagnostic category.

### DTC Descriptor

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 | P0116, P0118, P0119 | P0118*, P0119* | P0116*
Low Reference | -- | P0116, P0118, P0119 | P0118**, P0119** | P0116**
* Sensor damage may occur if the circuit is shorted to B+ ** Internal 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 | 143°C (289°F) | -40°C (-40°F) | -40°C (-40°F)¹
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

• | DTCs P0117, P0118, P0125, and P0128 are 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

• | The ECM detects that the ECT changed more than an expected value during a calibrated amount of time.

• | The condition exists for more than 4 seconds or an accumulation of 50 seconds over 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

• | 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 on either the ECT sensor signal circuit or the ECT sensor low reference circuit could set a DTC.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. Observe the engine coolant temperature (ECT) sensor parameter with a scan tool 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.

⇒ | Repair the suspected harness or connection if the ECT parameter fluctuates more than 3°C (5°F) while moving the related harnesses and connectors.

2. Inspect the engine coolant level. Verify that the cooling system is operating correctly.

⇒ | If you suspect a condition with engine cooling system, refer to Symptoms - Engine Cooling .

3. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. DTC P0119 should not set.

### Circuit/System Testing

1. Ignition OFF, disconnect the engine coolant temperature (ECT) sensor.
2. Ignition ON, verify that the scan tool ECT sensor parameter is at -40°C (-40°F).

⇒ | If greater than the specified value, test the signal circuit of the ECT sensor for a short to ground. If the circuit tests normal, replace the engine control module (ECM).

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+.

3. Test for less than 1 volt between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified value, test the low reference circuit for a short to B+. If the circuit tests normal, replace the ECM.

4. Ignition OFF, remove the fuse that supplies B+ to circuit terminal C2-56 of the ECM.
5. Test for less than 5 ohms between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

6. Install the fuse that supplies B+ to circuit terminal C2-56 of 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.

7. Ignition ON, install a 3A fused jumper wire between the signal circuit and the low reference circuit and verify the scan tool ECT sensor parameter is greater than 142°C (288°F).

⇒ | If less than the specified value, test the signal circuit of the ECT sensor for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

8. If all circuits test normal, test or replace the ECT sensor.

### Component Testing

1. Ignition OFF, disconnect the harness connector of the intake air temperature (ECT) sensor.

Important: A thermometer can be used to test the sensor off the vehicle.

2. 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.

⇒ | 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