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 provides 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, P0119 | P0118, P0119* | P0116*
Low Reference | -- | P0118, P0119 | P0118, P0119* | P0116*
* Internal ECM or ECT 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: -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 mutual performance of the ECT and the intake air temperature (IAT) signals. The ECM monitors the warm up and cool down behavior of the sensors, after a vehicle driven at operating temperature is shut down. If the ECM detects that the ECT is not with in a predetermined range of IAT after a long soak, or the ECT and IAT are not within a range of each other, as compared to a previous cold start, 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

#### Condition 1

• | Before the ECM can report DTC P0116 failed, DTC P0101 must run and pass.

• | DTC P0112, P0113, P0117, P0118, P0119, or P2610 is not set.

• | The engine run time of the previous ignition cycle was greater than 10 minutes.

• | The calculated engine cool down of the previous test was greater than 50°C (120°F).

• | The ignition was OFF for greater than 330 minutes after the previous engine shut down.

• | The accumulated air mass of the previous ignition cycle was greater than 6,000 grams.

• | DTC P0116 runs once an ignition cycle when the above conditions are met.

#### Condition 2

• | Before the ECM can report DTC P0116 failed, DTC P0101 must run and pass.

• | DTC P0112, P0113, P0117, P0118, or P0119 is not set.

• | The ECT at the previous engine shut down is greater than 82°C (180°F).

• | The block heater is not detected.

• | DTC P0116 runs once an ignition cycle when the above conditions are met.

### Conditions for Setting the DTC

• | The ECM determines the difference between the ECT and IAT at ignition ON is not within 15°C (26°F) of the difference recorded during a previous ignition cycle, when the enable conditions were met.

| OR

• | The ECM determines the IAT at ignition ON is within a calibrated range of the ECT and IAT recorded during a previous ignition cycle, but the ECT is not within 15°C (26°F) of the calibrated range.

• | The condition exists for greater than 4 seconds or cumulative of 50 seconds.

### Action Taken When the DTC Sets

DTC P0116 is a Type A/B DTC.

### Conditions for Clearing the MIL/DTC

DTC P0116 is a Type A/B DTC.

### Diagnostic Aids

• | Test the ECT and the IAT 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 and Temperature Versus Resistance - Intake Air 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.

• | A short to ground or voltage through a conductive material or fluid could set this DTC. Inspect the ECT sensor for evidence of coolant leaking into the connector body.

### 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. Ignition ON, observe the DTC information with a scan tool. DTC P0101, P0117, P0118, or P0119 should not be set.

⇒ | If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for diagnosis of the applicable DTC.

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 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 ECT sensor.
2. Remove the fuse that supplies B+ to circuit terminal X2-56 of the 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 battery positive voltage.

3. Test for less than 5 ohms between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified value, test the low reference circuit for an open/high resistance, or for a short to voltage. If the circuit tests normal, replace the ECM.

4. Install the fuse that supplies B+ to circuit terminal X2-56 of the ECM.
5. Ignition ON, verify 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.

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

6. Ignition ON, install 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).

⇒ | 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 ECM.

7. 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 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