P0116 Engine Coolant Temperature Sensor performance

P0116 code - The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return). When the engine is cold, the PCM will operate in open loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached.

The PCM uses inputs form the ECT sensor for the following calculations, for engine coolant temperature gauge operation through CCD or PCI (J1850) communications, injector pulse-widht, ASD relay shut down times, sprak-advance curves, idle Air Control (IAC) motor key-on steps, pulse-widht prime-short during cranking, O2 sensor closed loop times, purge solenoid on/off times, EGR solenoid on/off times (if equipped), leak detection pump operation (if equipped), radiator fan relay on/off times (if equipped), target idle speed.
The Engine off time is greater than 480 minutes, ambient temperature is greater than -64°C (-83°F), vehicle has been driven for one minute over 35 mph. Once the vehicle is soaked for a calibrated engine off time and then driven over the calibrated speed and load conditions for a calibrated time, the PCM compares the Ambient, Engine Coolant and Intake Air Temperature sensor values. Set conditions, if Ambient Air and Intake Air Temperature sensor agree with each other but engine coolant temperature does not agree with them, the engine coolant temperature sensor is declared as irrational. Default actions, MIL Light will illuminate.

Possible causes:

• High resistance in the ECT Signal circuit.
• High resistance in the sensor ground circuit.
• Engine Coolant Temperature (ECT) sensor.
• Powertrain Control Module (PCM).

Diagnose code P0116-Engine Coolant Temperature Sensor performance

Step 1. Check for an active condition

Turn the ignition off, allow the vehicle to sit with the ignition off in an environment where the temperature is consistent and above -64°C (-83°F) until the engine coolant temperature is equal, or close to the environmental ambient temperature. Turn the ignition on, with the scan tool, compare the AAT, ECT, and IAT sensor values.

Is the Engine Coolant Temperature sensor value within 15°C (59°F) of the other two sensor values?

Yes, perform the PCM intermittent condition.
No, go to step 2.

Step 2. Check for high resistance in the ECT Signal circuit
Turn the ignition off, disconnect the ECT Sensor harness connector. Disconnect the PCM Harness connector. Measure the resistance of the ECT Signal circuit between the ECT sensor harness connector and the PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 3.
No, repair the ECT signal circuit for an open or high resistance.

Step 3. Check for high resistance in the sensor ground circuit
Measure the resistance of the sensor ground circuit between the ECT sensor harness connector and PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 4.
No, repair the sensor ground circuit for an open or high resistance.

Step 4. ECT sensor voltage
Turn the ignition off, reconnect the PCM harness connector. Turn the ignition on, with the scan tool, read the ECT sensor voltage. The sensor voltage should be approximately 5.0 volts (plus or minus 0.1 volts) with the connector disconnected. Connect a jumper the ECT signal circuit and the sensor ground circuit at the ECT sensor harness connector. The sensor voltage should be approximately 0.0 volts (plus or minus 0.1 volts) with the jumper in place.

Does the scan tool display the voltage as described above?

Yes, replace the Engine Coolant Temperature (ECT) sensor.
No, go to step 5.

Step 5. Check related PCM and component connections

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