Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | 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 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, P0128 |
Low Reference | -- | P0118 | P0118 | P0118 | 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 (303°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 control module supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the control module detects a high voltage on the ECT signal circuit. With lower sensor resistance, the control module detects a lower voltage on the ECT signal circuit. If the control module detects an excessively low ECT signal voltage, which is a high temperature indication, DTC P0117 sets. If the control module detects an excessively high ECT signal voltage, which is a low temperature indication, DTC P0118 sets.
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 conditions are 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 conditions are 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
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
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. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the ECT sensor.
- Ignition OFF for 90 seconds, test for less than 5 ohms of resistance between the low reference circuit terminal A and ground.
- Ignition ON, verify the scan tool ECT parameter is less than -39°C (-38°F).
- Install a 3A 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 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 terminal B 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
