P0117

P0117-ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT LOW





For a complete wiring diagram refer to Diagrams/Electrical.


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 PCM detects that the Engine Coolant Temperature Sensor input voltage is below the minimum acceptable value. One Trip Fault. Three good trips to clear the MIL. The MIL and ETC light will illuminate if equipped.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.


Diagnostic Test


1. ACTIVE DTC

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


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.


NOTE: Diagnose and repair any system voltage DTCs before continuing with this test.

With the scan tool, select View DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition


2. ECT SENSOR

Turn the ignition off.

Disconnect the ECT harness connector.

Ignition on, engine not running.

With a scan tool, read ECT voltage.


NOTE: The sensor voltage should be approximately 5.0 volts (plus or minus .1 volt) with the connector disconnected.

Does the scan tool display the voltage as described above?

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.

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.

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. EXCESSIVE RESISTANCE IN THE (K2) ECT SIGNAL CIRCUIT





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 to perform diagnosis.

Measure the resistance of the (K2) ECT Signal circuit between the Engine Coolant Temperature Sensor harness connector and the appropriate terminal of special tool #8815.

Is the resistance below 5.0 ohms?

Yes

- Go To 6

No

- Repair the excessive resistance in the (K2) ECT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test


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

- 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