P0117

DTC P0117 or P0118

DTC Descriptors

DTC P0117
- Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage

DTC P0118
- Engine Coolant Temperature (ECT) Sensor Circuit High Voltage

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview






Typical Scan Tool Data






Circuit/System Description

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5 volts to the ECT sensor signal circuit and supplies a ground for the low reference circuit.

Conditions for Running the DTC

P0117
* The engine run time is more than 3 seconds.
OR
The ignition is ON and the IAT parameter is less than 90°C (194°F).
* The diagnostic runs continuously when the above condition is met.

P0118
* The engine is running for more than 30 seconds.
OR
The ignition is ON and the IAT parameter is more than 0°C (32°F).
* The diagnostic runs continuously when the above condition is met.

Conditions for Setting the DTC

P0117

The control module detects that the ECT sensor parameter is more than 139°C (282°F) for more than 24 seconds.

P0118

The control module detects that the ECT sensor parameter is less than -37°C (-35°F) for more than 24 seconds.

Action Taken When the DTC Sets

DTCs P0117 and P0118 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0117 and P0118 are Type B DTCs.

Diagnostic Aids

* An overheating condition may cause this DTC to set.
* After starting the engine, the ECT sensor temperature should rise steadily to about 90°C (194°F), then stabilize after the thermostat opens.
* If a short to a separate voltage source occurs, this DTC may set and damage the ECT sensor.

Circuit/System Verification

Caution: Under pressure, the temperature of the solution in the radiator can be considerably higher, without boiling. Removing the radiator cap while the engine is hot (pressure is high), will cause the solution to boil instantaneously, with explosive force. The solution will spew out over the engine, fenders, and the person removing the cap. Serious bodily injury may result. Flammable antifreeze, such as alcohol, is not recommended for use at any time. Flammable antifreeze could cause a serious fire.

1. Turn OFF the ignition.
2. Inspect the cooling system surge tank for the proper coolant level.
3. If the ignition has been OFF for 8 hours or more, the ECT and the IAT should be within 15°C (27°F) of each other and also the ambient temperature. Turn ON the ignition, with the engine OFF, and use a scan tool to observe the IAT and the ECT sensor parameters.
4. Use the scan tool to verify the proper operation of the engine cooling system fans.

Important: A critical analysis of the operation of the thermostat is necessary to properly diagnose these DTCs.

5. Verify the proper heat range, and the operation of the thermostat. Refer to Thermostat Diagnosis. Component Tests and General Diagnostics

Circuit/System Testing

Important: All electrical components and accessories must be turned OFF and allowed to power down.

1. Ignition OFF, disconnect the harness connector at the ECT sensor.
2. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal A and ground.

^ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, verify the scan tool ECT parameter is less than -39°C (-38°F).

^ If greater than the specified range, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the ECM.

4. Install a 3-amp fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the scan tool ECT parameter is greater than 149°C (300°F).

^ If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test or replace the ECT sensor.

Component Testing

Measure and record the resistance of the ECT sensor at various ambient temperatures, then compare those measurements to the Temperature vs Resistance table.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Engine Coolant Temperature Sensor Replacement
* Programming and Relearning Programming and Relearning