P0117
P0117-ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT LOWP0117 - Engine Coolant Temperature Sensor Circuit Low:
Theory of Operation
The engine coolant temperature sensor is a negative temperature coefficient thermistor-type sensor whose resistance varies inversely with temperature. At cold temperatures the sensor resistance is high so the voltage is high. As the coolant temperature increases the resistance decreases and the voltage becomes low.
WHEN MONITORED:
With the ignition on. Battery voltage greater than 10.4 volts.
SET CONDITION:
The Engine Coolant Temperature (ECT) sensor circuit voltage at the PCM is less than 0.078 of a volt for more than 2.8 seconds. One Trip Fault. Three good trips to clear the MIL.
POSSIBLE CAUSES
- (K2) ECT signal circuit shorted to ground
- (K2) ECT signal circuit shorted to the (K900) sensor ground circuit
- ECT sensor
- PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
DIAGNOSTIC TEST
1. ECT SENSOR VOLTAGE BELOW 0.078 OF A VOLT
Ignition on, engine not running.
With a scan tool, read the ECT voltage.
Q: Is the voltage below 0.078 of a volt?
YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Component Tests and General Diagnostics
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
2. ECT SENSOR
Turn the ignition off.
Disconnect the ECT harness connector.
Ignition on, engine not running.
With a scan tool, read ECT voltage.
Q: Is the voltage above 1.0 volt?
YES: Replace the ECT Sensor. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 3
3. (K2) ECT SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
Turn the ignition off.
Disconnect the C2 PCM harness connector.
Measure the resistance between the (K900) Sensor ground circuit and the (K2) ECT Signal circuit in the ECT Sensor harness connector.
Q: Is the resistance below 5.0 ohms?
YES: Repair the short to between the (K900) Sensor ground circuit and the (K2) ECT Signal circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 4
4. (K2) ECT SIGNAL CIRCUIT SHORTED GROUND
Measure the resistance between ground and the (K2) ECT Signal circuit in the ECT Sensor harness connector.
Q: Is the resistance below 100 ohms?
YES: Repair the short to ground in the (K2) ECT Signal circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 5
5. 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.
Q: Were there any problems found?
YES: Repair as necessary. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Replace and program the Powertrain Control Module. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test