Low Engine Coolant Indicator Always On

Low Engine Coolant Indicator Always On (LH2/LC3)

Diagnostic Instructions

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

Diagnostic Fault Information





Circuit/System Description

The low engine coolant level indicator is controlled by the body control module (BCM) through the low speed GM LAN Serial Data line to the engine control module (ECM). The normal state of the engine coolant level switch is closed when in contact with coolant.

Reference Information
Schematic Reference

Engine Cooling Schematics
Connector End View Reference

Cooling System Connector End Views
Description and Operation

Cooling System Description and Operation
Electrical Information Reference

* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs

Scan Tool Reference

Scan Tool Output Controls

Circuit/System Verification

The low coolant indicator should be OFF with the engine coolant at the proper level.

Circuit/System Testing

Important: Circuit/System Verification must be performed before performing the Circuit/System Testing.

1. Ignition OFF, disconnect the harness connector at the coolant level switch.
2. Install a 3A fused jumper wire between the signal circuit terminal and ground.
3. Engine running, verify the low coolant indicator turns OFF.

* If the indicator does not turn OFF, test the signal circuit for an open/high resistance.
* If the indicator turns OFF, test the ground circuit for an open/high resistance.

4. If all circuits test normal, replace the coolant level switch.

Repair Instructions

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

* Surge Tank Replacement
* Control Module References
* Instrument Cluster Replacement

Repair Verification

Verify that the low coolant indicator is OFF with the engine coolant at the proper level.