NGC

P0117-ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT LOW





For a complete wiring diagram Consult 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 and 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.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Initial Inspection and Diagnostic Overview

Diagnostic Test

1. DTC IS ACTIVE
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 *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC

2. (K2) ECT SIGNAL CIRCUIT SHORTED TO GROUND




Turn the ignition off.
Disconnect the Engine Coolant Temperature Sensor connector.
Disconnect the C2 Powertrain Control Module (PCM) connector.
Measure the resistance between ground and the (K2) ECT Signal circuit in the Engine Coolant Temperature Sensor harness connector.
Is the resistance above 100 ohms?

Yes

- Go to 3

No

- Repair the short to ground in the (K2) ECT Signal circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

3. (K2) ECT SIGNAL CIRCUIT SHORTED TO (K900) SENSOR GROUND CIRCUIT




Measure the resistance between the (K2) ECT Signal circuit and the (K900) Sensor Ground circuit in the Engine Coolant Temperature Sensor harness connector.
Is the resistance above 100 ohms?

Yes

- Go to 4

No

- Repair the short between the (K2) ECT Signal circuit and the (K900) Sensor Ground circuit.
- Perform the PCM Verification Test. Powertrain Verification Test

4. 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 5

No

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

5. ENGINE COOLANT TEMPERATURE SENSOR
Turn the ignition off.
Connect the Powertrain Control Module (PCM) connector.
Turn the ignition on.
With the scan tool, read the Engine Coolant Temperature Sensor signal 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

- Verify that there is good pin to terminal contact in the Engine Coolant Temperature Sensor and Powertrain Control Module connectors. Replace the ECT Sensor if no problems were found in the connectors.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 6

6. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Engine Coolant Temperature Sensor and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Verify that there is good pin to terminal contact in the Engine Coolant Temperature Sensor and Powertrain Control Module connectors.
Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
Look for the data to change or for the DTC to reset during the wiggle test.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Replace and program the Powertrain Control Module (PCM).
- Perform the PCM Verification Test.Powertrain Verification Test