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 | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
ECT Sensor Signal | P0117 | P0118 | P0118 | P0118 | P0116, P0119, P0128
Low Reference | -- | P0118 | P0118 | P0118 | P0119, P0128

### Typical Scan Tool Data

#### ECT Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The ignition is ON, or the engine is running Parameter Normal Range: Varies with ambient temperature, within a range of -39 to +120°C (-38 to +248°F)
ECT Sensor Signal | 140°C (284°F) | -40°C (-40°F) | -40°C (-40°F)
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)

### Circuit/System 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 a ground for the low reference circuit.

The purpose of this diagnostic is to analyze the performance of the ECT sensor by comparing the response and the range of the sensor signal to two distinct models under various operating conditions.

• | The first model verifies that the sensor is not stuck in range.

• | The second model verifies that the sensor is within an acceptable operating range of the calculated ECT.

| Both models use various parts of the information derived from the following inputs:

- | Ambient air temperature (AAT)

- | ECT

- | Engine OFF time

- | Engine run time

- | Intake air temperature (IAT)

- | Mass air flow (MAF)

### Conditions for Running the DTC

#### P0116 - Engine Running, Sensor Signal Stuck Test

• | DTC P0116 signal range test, P0117, or P0118 is not set.

• | The ECT at engine start is colder than 76°C (169°F).

• | The ignition is ON, or the engine is running.

• | The ignition voltage is greater than 10 volts.

• | This model of the DTC runs continuously within the enabling conditions.

#### P0116 - Engine Running, Sensor Within Range Test

• | DTC P0111, P0112, P0113, P0114, P0116 signal stuck test, P0117, or P0118 is not set.

• | The AAT at engine start is warmer than -10°C (14°F).

• | The engine is running.

• | The engine OFF timer is greater than 420 minutes.

• | The engine OFF timer signal is plausible.

• | The IAT at engine start is between -10° and +50°C (14-122°F).

• | The IAT at engine start minus the AAT at engine start is less than 10°C (18°F).

• | The ignition voltage is greater than 10 volts.

• | This model of the DTC runs once per drive cycle within the enabling conditions.

### Conditions for Setting the DTC

#### P0116 - Engine Running, Sensor Signal Stuck Test

• | The ECT back up value minus the ECT back up value at engine start, is not within range of the calibrated model.

• | The measured ECT minus the measured ECT at engine start, is not within range of the calibrated model.

#### P0116 - Engine Running, Sensor Within Range Test

• | The ECT at engine start is not within range of the calibrated model.

• | The ECT at engine start minus the IAT at engine start is not within range of the calibrated model.

### Action Taken When the DTC Sets

• | DTC P0116 is a Type B DTC.

• | The cooling fans will be commanded ON.

• | The AC compressor will be commanded OFF.

### Conditions for Clearing the MIL/DTC

DTC P0116 is a Type B DTC.

### Diagnostic Aids

• | Engine coolant that is leaking through the sensor will create a high resistance short to ground. This condition results in less voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a warmer ECT.

• | The engine OFF time information is generated in the infotainment module, and sent to the ECM via the controller area network (CAN).

• | The AAT sensors respond quickly to temperature changes, however the ECM processes an extremely large number of samples before it updates the information that is sent to the scan tool. An update to the scan tool Ambient Temperature parameter may not occur until the next drive cycle.

• | It is not possible to swing the scan tool Ambient Temperature parameter warm or cold as is usually done with traditional methods of testing when servicing the intake air temperature (IAT) sensor or the engine coolant temperature (ECT) sensor.

• | The resistance of the AAT sensors respond quickly to temperature changes. These changes can be monitored with a DMM. Simply placing the sensor in a refrigerator or freezer and then removing it after several minutes will induce a rapid change in the resistance measurement as it warms up.

• | The AAT sensors are identical and can be exchanged with each other for testing purposes.

### 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. Turn OFF the ignition.
2. Inspect the cooling system surge tank for the proper engine coolant level. Refer to Cooling System Leak Testing and Cooling System Draining and Filling.
3. If the ignition has been OFF for 8 hours or greater, the IAT, the ambient temperature, and the ECT should be within 9°C (16°F) of each other. Ignition ON, observe the scan tool IAT Sensor, Ambient Temperature, and the ECT Sensor parameters. Compare those sensor parameters to each other and also to the ambient temperature to determine if the ECT sensor is skewed warmer or colder.
4. Engine running, observe the ECT Sensor parameter. The reading should be between -39 to +120°C (-38 to +248°F) depending on the current ambient temperature and the vehicle operating conditions.
5. Engine operating at idle, observe the scan tool MAF Sensor parameter. The reading should be between 2-8 g/s.
6. Drive the vehicle under various operating conditions. Observe the scan tool IAT Sensor parameter and the Ambient Temperature parameter. The readings should be near each other.
7. 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. Verify that debris is not blocking the airflow through the front of the grille area.
2. Verify that the port of the passenger side AAT sensor is free of debris and contamination.
3. Inspect the MAF/IAT sensor elements for contamination, and debris.
4. Ignition OFF for 90 seconds, disconnect the harness connector at the ECT sensor.
5. Inspect the ECT sensor terminals for corrosion and for engine coolant leaking through the sensor.
6. 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.

7. Disconnect the ECM.
8. Test the ECT signal circuit between terminal 1 and ECM connector X 1 terminal 60 for less than 5 ohms.

⇒ | If greater than the specified range, test the signal circuit for a high resistance.

9. If the circuits test normal, test or replace the ECT sensor.

### Component Testing

• | Measure and record the resistance of the ECT sensor at various ambient temperatures, then compare those measurements to the Temperature Versus Resistance table.

• | Measure and record the resistance of the IAT sensor at various ambient temperatures, then compare those measurements to the Temperature Versus Resistance table.

• | Remove the AAT sensor and allow it to rest on a workbench away from sunlight and any direct heat or cold source. Connect the DMM to the sensor, and measure the resistance at an ambient temperature of 22-23°C (72-73°F). The resistance should measure between 4.9-5.4K ohms.

### 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