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 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 | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
ECT Sensor Signal | P0117 | P0118 | P0118 | P0116, P0128 |
Low Reference | -- | P0118 | P0118 | P0118 |
Typical Scan Tool Data
Circuit | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
Operating Conditions: Key ON, engine OFF | ||||
ECT Sensor Signal | -39 to +135°C (-38 to +275°F) | 135°C (275°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 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 ECM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the ECT signal circuit.
Conditions for Running the DTC
P0117
| • | DTC P0118 is not set. |
| • | The ignition is ON. |
| • | Battery voltage is between 10-16 V. |
P0118
| • | DTC P0117 is not set. |
| • | The engine has been running for more than 1 second. |
| • | Battery voltage is between 10-16 V. |
Conditions for Setting the DTC
P0117
ECT sensor voltage is less than 0.1 V.
P0118
ECT sensor voltage is more than 4.9 V.
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
| • | If a short to a separate 5-volt source occurs, this DTC will set. |
| • | A skewed sensor could result in poor driveability conditions. |
| • | After starting the engine, the ECT should rise steadily, then stabilize when the thermostat opens. |
| • | If the condition is suspected of being intermittent, refer to Testing for Intermittent Conditions and Poor Connections and Inducing Intermittent Fault Conditions. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Start the engine.
- Observe the ECT sensor parameter with a scan tool.
- The ECT sensor parameter should be within normal operating range.
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
- Ignition OFF, disconnect the harness connector at the ECT sensor.
- Ignition OFF, test for less than 5 ohms of between the low reference circuit terminal A and ground.
- Ignition ON, verify the scan tool ECT parameter is less than -39°C (-40°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 135°C (275°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. |
Component Testing
Measure and record the resistance of the ECT sensor at various ambient temperatures and 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 |
