Engine Oil Temperature Indicator Always On

Engine Oil Temperature Indicator Always On

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



Diagnostic Fault Information






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 (IPC) 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 to -165°C (-40 to +329°F).


Reference Information
Schematic Reference

Instrument Cluster Schematics (Instrument Cluster Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

* Instrument Cluster Description and Operation (Description and Operation)
* Indicator/Warning Message Description and Operation (Indicator/Warning Message Description and Operation)

Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)


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 between the low reference circuit terminal A (LS7) or terminal C (LS2) and ground.

• If greater than 1 ohm, test the 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 terminal B for a short to ground. If the circuit tests normal, replace the IPC.

4. Ignition ON, install a 3A fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A (LS7) or terminal C (LS2). Verify the scan tool Engine Oil Temperature Calculated parameter is greater than 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

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Engine Oil Pressure Sensor and/or Switch Replacement (Service and Repair) for the 6.0L engine
* Engine Oil Temperature Gage Sensor Replacement (Service and Repair) for the 7.0L engine
* Control Module References (Programming and Relearning) for the IPC replacement, setup, and programming