For 1990-2009 cars only
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 014: Engine Coolant Temperature (ECT) Sensor Circuit High VoltageDTC 015: Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage
Circuit Description
The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The 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 Setting the DTC
014
| • | The engine is running for greater than 2 minutes. |
| • | The engine coolant temperature sensor signal voltage indicates a coolant temperature greater than 146°C (294°F). |
| • | The DTC runs continuously when the above condition is met. |
015
| • | The engine is running for greater than 2 minutes. |
| • | The engine coolant temperature sensor signal voltage indicates a coolant temperature greater than -35°C (-31°F). |
| • | The DTC runs continuously when the above condition is met. |
Diagnostic Aids
| • | After starting the engine, the ECT sensor temperature should rise steadily, then stabilize after the thermostat opens. |
| • | 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 driveability condition. |
| • | If the vehicle has set overnight, the ECT sensor and the intake air temperature (IAT) sensor values should display within 3°C (5°F). |
Reference Information
Schematic Reference
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Engine running, DTC 014 and 015 should not set.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the engine coolant temperature (ECT) sensor.
- Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal B and ground.
- Ignition ON, verify the scan tool ECT sensor parameter is at -40°C (-40°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 sensor parameter is greater than 180°C (356°F).
- If all circuits test normal, test or replace the ECT sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM. |
Important: If the signal circuit of the ECT sensor is shorted to voltage the ECT sensor may be damaged.
| ⇒ | If less than the specifed 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
- 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 table and verify that the resistance is within 5 percent of the specification.
Important: A thermometer can be used to the used to test the sensor off the vehicle.
| ⇒ | If not within the specified range, 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 |
