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 | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
ECT Sensor Signal | P0117 | P0118, P0119 | P0118, P0119* | P0116 |
Low Reference | -- | P0118, P0119 | P0118, P0119* | P0116 |
* Sensor or ECM damage may occur if the circuit is shorted to B+ | ||||
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine operating in Closed Loop. Parameter Normal Range: -39 to 142°C (-38 to 288°F) Varies with coolant temperature. | |||
ECT Sensor Signal | 143°C (289°F) | -40°C (-40°F) | -40°C (-40°F)* |
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)* |
* Internal ECM or ECT sensor damage may occur if the circuit is shorted to B+ | |||
Circuit 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.
The following table illustrates the difference between temperature, resistance, and voltage:
ECT | ECT Resistance | ECT Signal Voltage |
|---|---|---|
Cold | High | High |
Warm | Low | Low |
Conditions for Running the DTC
P0117
| • | The engine is operating. |
| • | The start up intake air temperature (IAT) is less than 72°C (161°F). |
OR
| • | The start up intake air temperature (IAT) is greater than 72°C (161°F). |
| • | The engine run time is greater than 59 seconds. |
| • | The DTC runs continuously once the above conditions are met. |
P0118
| • | The ignition is ON or the engine is operating. |
| • | The DTC runs continuously once the above condition is met. |
Conditions for Setting the DTC
P0117
The ECM detects that the ECT is greater than 140°C (284°F) for greater than 1 seconds or a cumulative of 10 seconds, 4 seconds or a cumulative of 30 seconds for LLT.
P0118
The ECM detects that the ECT is less than -39°C (-38°F) for greater than 1 seconds or a cumulative of 10 seconds, 4 seconds or a cumulative of 30 seconds for LLT.
Action Taken When the DTC Sets
DTC P0117 and P0118 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTC P0117 and P0118 are Type B DTCs.
Diagnostic Aids
| • | Test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a DTC or a driveability condition. Refer to Temperature Versus Resistance - Engine Coolant Temperature Sensor . |
| • | If the vehicle has sat overnight, the IAT sensor and the ECT sensor values should display within 3°C (5°F). |
| • | After starting a cold engine, the ECT sensor temperature should rise steadily, then stabilize after the thermostat opens. |
| • | High resistance in the circuits of either the ECT or IAT sensor could set a DTC. |
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
- Engine idling for 1 minute. Observe the DTC information with a scan tool. DTCs P0117 and P0118 should not set.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
- Ignition OFF, disconnect the ECT sensor.
- Ignition ON, verify that the scan tool ECT sensor parameter is at -40°C (-40°F).
- Test for less than 1 volt between the low reference circuit terminal 2 and ground.
- Ignition OFF, remove the fuse that supplies B+ to circuit terminal X2-56 of the ECM.
- Test for less than 5 ohms between the low reference circuit terminal 2 and ground.
- Install the fuse that supplies B+ to circuit terminal X2-56 of the ECM.
- Ignition ON, connect a 3A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool ECT sensor parameter is greater than 142°C (288°F).
- If all circuits test normal, test or replace the ECT sensor.
| ⇒ | If greater than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM. |
Notice: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.
Important: The control module or the sensor may be damaged if the circuit is shorted to B+.
| ⇒ | If greater than the specified value, test the low reference circuit for a short to B+. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
Important: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.
| ⇒ | If less than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
Component Testing
- Ignition OFF, disconnect the harness connector at the engine coolant temperature (ECT) sensor.
- Test the ECT sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Temperature Versus Resistance - Engine Coolant Temperature Sensor table and verify that the resistance is within 5 percent of the specification.
Important: A thermometer can be used to test the sensor off the vehicle.
| ⇒ | If not within the specified value, replace the ECT sensor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for engine control module replacement, setup, and programming |
