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 P0116: Engine Coolant Temperature (ECT) Sensor Performance

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
ECT Sensor Signal | P0117 | P0118 | P0118¹ | P0116
Low Reference | -- | P0118 | P0118¹ | P0116
¹ ECM or sensor 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: Varies with ambient temperature
ECT Sensor Signal | 214°C (417°F) | -40°C (-40°F) | -40°C (-40°F)¹
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)¹
¹ ECM or 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 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, P0128, and P0217 are not set.

• | The engine is operating.

• | The ignition has been off for greater than 6 hours before vehicle is started.

• | The DTC runs when the above conditions are met.

### Conditions for Setting the DTC

The ECM does not detect an ECT sensor change of greater than 3°C (5°F).

### Action Taken When the DTC Sets

DTC P0116 is a Type B DTC.

### Conditions for Clearing the MIL/DTC

DTC P0116 is a Type B DTC.

### Diagnostic Aids

• | After starting the engine, the ECT sensor temperature should rise steadily, then stabilize after the thermostat opens.

• | 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 driveability condition. Refer to Temperature Versus Resistance .

• | Inspect for the correct operation of the engine cooling system and verify the correct coolant level.

### 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. Verify that the following DTCs are not set: P0112, P0113, P0117, P0118, P0125, or P0128.

⇒ | If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. 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. DTC P0116 should not set.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the ECT sensor.
2. Ignition ON, clear the DTC information with a scan tool.
3. 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 for a short to ground. If the circuit tests normal, replace the ECM.

4. Test for less than 0.5 volt between the low reference circuit and ground.

⇒ | If greater than specified value, test the low reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

5. Ignition OFF, test for less than 5 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, replace the ECM.

6. Ignition ON, clear the DTC information with a scan tool.

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

7. Install a 1A fused jumper wire between the signal circuit and the low reference circuit. Verify the ECT sensor parameter is greater than 128°C (262°F).

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

Important: A thermometer can be used to the 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 table and verify that the resistance is within 5 percent of the specification.

⇒ | If the resistance vs. temperature is not within 5 percent, 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 ECM replacement, setup, and programming