DTC Descriptors
DTC P0117: Engine Coolant Temperature (ECT) Sensor Circuit Low VoltageDTC P0118: Engine Coolant Temperature (ECT) Sensor Circuit High Voltage
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
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 (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
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 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
DTC Type Reference
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the ECT sensor.
- Ignition OFF, test for less than 5 ohm of resistance between the low reference circuit terminal A and ground.
- Ignition ON, verify the scan tool ECT parameter is less than -38°C (-36°F).
- Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool ECT parameter is greater than 138°C (280°F).
- If all circuits test normal, test or replace the ECT sensor.
Important:
• The cooling fans are commanded ON when certain DTCs are set. • If shorted to voltage occurs, the ECT sensor may be damaged.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the control module. |
| ⇒ | If greater than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the control module. |
| ⇒ | 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 control module. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
| • | Control Module References for engine control module (ECM) replacement, setup, and programming |
