Engine Oil Temperature Indicator Always On

Engine Oil Temperature Indicator Always On

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview






Circuit/System Description

The engine oil temperature sensor is a thermistor that varies in resistance as the engine oil temperature changes. A low engine oil temperature produces a high resistance at the engine oil temperature sensor. A high engine oil temperature produces a low resistance at the engine oil temperature sensor. The engine control module (ECM) with the engine oil temperature sensor via a discreet signal circuit and low reference circuit. The ECM applies 5 volts to the engine oil temperature sensor and calculates temperature based on the engine oil temperature sensor voltage. The engine oil temperature range is between -40°C (-40°F) to -165°C (329°F).

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the engine oil temperature sensor.
2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit and ground.

• If greater than 1 ohm, test the low reference circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Engine Oil Temperature Calculated parameter is less than -10°C (14°F)

• If not, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

4. Ignition ON, install a 3-A fused jumper wire between the signal circuit and the low reference circuit. Verify the scan tool Engine Oil Temperature Calculated parameter is greater the 150°C (302°F).

• If not, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test or replace the engine oil temperature sensor.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Engine Oil Level Sensor and/or Switch Replacement for the 4.4L engine
* Refer to Programming and Relearning Programming and Relearning