Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provide an overview of each diagnostic category. |
DTC Descriptors
DTC P0117: Engine Coolant Temperature (ECT) Sensor Circuit Low VoltageDTC P0118: Engine Coolant Temperature (ECT) Sensor Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
ECT Sensor Signal | P0117 | P0118 | P0118 | P0118 | P0116, P0125, P0128 |
Low Reference | -- | P0118 | P0118 | P0118 | P0125, P0128 |
Typical Scan Tool Data
Circuit | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
ECT Sensor Signal | -39 to +120°C (-38 to +248°F) | 150°C (302°F) | -40°C (-40°F) | -40°C (-40°F) |
Low Reference | -- | -- | -40°C (-40°F) | -40°C (-40°F) |
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 signal circuit and supplies a ground to the low reference circuit.
Conditions for Running the DTC
P0117
| • | The engine is running for more than 10 seconds. |
| OR |
| • | The ignition is ON when the intake air temperature (IAT) is less than 50°C (122°F). |
| • | This DTC runs continuously within the enabling conditions. |
P0118
| • | The engine is running for more than 10 seconds. |
| OR |
| • | The ignition is ON when the IAT is more than 0°C (32°F). |
| • | This DTC runs continuously within the enabling conditions. |
Conditions for Setting the DTC
P0117
The ECM detects that the ECT is more than 149°C (300°F) for more than 5 seconds.
P0118
The ECM detects that the ECT is less than -39°C (-38°F) for more than 5 seconds.
Action Taken When the DTC Sets
DTCs P0117 and P0118 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0117 and P0118 are Type B DTCs.
Reference Information
Schematic Reference
Connector End View Reference
Engine Controls Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Verification
- Turn OFF the ignition.
- Inspect the cooling system surge tank for the proper engine coolant level. Refer to Cooling System Leak Testing and Cooling System Draining and Filling .
- Turn ON the ignition, with the engine OFF.
- Use the scan tool to verify the proper operation of the engine cooling system fans.
- Turn OFF the ignition.
- Verify the proper heat range, and the operation of the thermostat. Refer to Thermostat Diagnosis .
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.
Circuit/System Testing
Important: All electrical components and accessories must be turned OFF and allowed to power down.
- Ignition OFF, disconnect the ECT harness connector at the ECT sensor.
- Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit and ground.
- Ignition ON, verify the scan tool ECT Sensor parameter is less than -39°C (-38°F).
- Install a 3A fused jumper wire between the signal circuit and the low reference circuit. Verify the scan tool ECT Sensor parameter is greater than 149°C (300°F).
- If all circuits test normal, test or replace the ECT sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | 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. |
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. Refer to Temperature Versus Resistance .
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
