P0116–ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT PERFORMANCE





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


Engine Coolant Temperature Sensor performance looks at the outputs of three temperature sensors and compares them under cold start conditions. Following a start to run delay time, the outputs of the ambient, engine coolant, and intake air temperature sensors will be compared. If the intake air and ambient air temperature sensors agree and the engine coolant temperature does not agree, the engine coolant temperature sensor is declared as irrational.


Possible Causes
EXCESSIVE RESISTANCE IN THE (K2) ECT SIGNAL CIRCUIT
EXCESSIVE RESISTANCE IN THE (K900) SENSOR GROUND CIRCUIT
ECT SENSOR
PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1. ACTIVE DTC

Start the engine.
Allow the engine to reach normal operating temperature.
With a scan tool, select View DTCs.

NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.



Is the DTC Active or Pending at this time?

Yes


No

2. ECT SENSOR VOLTAGE ABOVE 4.6 VOLTS

Turn the ignition off.
Disconnect the ECT Sensor harness connector.
Ignition on, engine not running.
With a scan tool, read the ECT voltage.

Is the voltage above 4.6 volts?

Yes


No

3. ECT SENSOR



Connect a jumper wire between the (K2) ECT Signal circuit and the (K900) Sensor ground circuit in the ECT Sensor harness connector.
With a scan tool, read the ECT voltage.

Is the voltage below 1.0 volt with the jumper wire installed?

Yes


No

4. EXCESSIVE RESISTANCE IN THE (K2) ECT SIGNAL CIRCUIT

Turn the ignition off.
Disconnect the C2 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 and #8815-1 to perform diagnosis.


Using a voltmeter perform a voltage drop test. Backprobe the (K2) ECT Signal circuit at the ECT Sensor harness connector and probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.


Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes


No

5. EXCESSIVE RESISTANCE IN THE (K900) SENSOR GROUND CIRCUIT

Turn the ignition off.
Move the voltmeter leads to backprobe the (K900) Sensor Ground circuit at the ECT Sensor harness connector and to probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is indicated on the voltmeter.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.


Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes


No

6. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.


Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes


No