P0117
DTC P0117 or P0118
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
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
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
DTC P0117 and P0118 are Type B DTCs.
Conditions for Clearing the DTC
DTC P0117 and P0118 are Type B DTCs.
Diagnostic Aids
* An overheating condition may cause DTC P0117 to set if an overheating condition is found. Refer to Engine Overheating. Engine Overheating
* Inspect the ECT sensor terminals for corrosion and for engine coolant leaking through the sensor. Engine coolant that is leaking through the sensor will create a high resistance short to ground. This condition results in less voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a warmer ECT.
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. Engine idling, DTC P0117 or P0118 should not set.
2. If the vehicle passes the Circuit/System Verification test, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records list.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the ECT sensor.
2. Ignition OFF for 90 seconds, 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.
* Engine Coolant Temperature Sensor Replacement
* Control Module References Programming and Relearning Verification Tests