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 Descriptor
DTC P0117 00: Engine Coolant Temperature Sensor Circuit Low VoltageDTC P0118 00: Engine Coolant Temperature Sensor Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Signal | P0117 | P0118 | P0118 | -- |
Low Reference | -- | P0118 | -- | -- |
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. | |||
Signal | 149°C (300°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 V 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
| • | The ignition is ON. |
| • | The engine speed is greater than 1 000 RPM. |
Conditions for Setting the DTC
P0117
The ECM detects the ECT voltage is below the threshold
P0118
The ECM detects the ECT voltage is above the threshold
Action Taken When the DTC Sets
DTCs P0117 and P0118 are Type B DTCs
Conditions for Clearing the DTC
DTCs 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. |
| • | If the engine has sat overnight, the intake air temperature (IAT) sensor and the engine coolant temperature (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 may 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 running for 60 s. 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 harness connector at the B34 Engine Coolant Temperature (ECT) Sensor.
- Ignition OFF, test for less than 5 Ω between the low reference circuit terminal 2 and ground.
- Ignition ON, verify the scan tool ECT Sensor is at -40°C (-40°F).
- Ignition ON, connect a 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool ECT Sensor parameter is greater than 142°C (288°F).
- If all circuits test normal, test or replace the B34 Engine Coolant Temperature (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 K20 Engine Control Module (ECM). |
| ⇒ | If greater than the specified range, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM). |
Note: 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 range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM). |
Component Testing
Static Test
- Ignition OFF, disconnect the harness connector at the B34 Engine Coolant Temperature (ECT) Sensor.
- Test and record the resistance between the signal circuit terminal 2 and the low reference circuit terminal 1 at various ambient temperatures. Compare those measurements to the Temperature Versus Resistance table and verify that the resistance is within 5% of the specification.
| ⇒ | If not within the specified range, replace the B34 Engine Coolant Temperature (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 |
