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 instrument panel cluster interfaces with the engine oil temperature sensor via a discreet signal circuit and low reference circuit. The IPC applies 5 volts to the engine oil temperature sensor through an internal input resistor that is connected to the signal circuit of the engine oil temperature sensor. The internal resistor in the IPC measures the voltage and calculates temperature. 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 IPC.

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 IPC.

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 6.0L engine
* Engine Oil Temperature Gage Sensor Replacement for the 7.0L engine
* Control Module References for the IPC replacement, setup, and programming