Low Engine Coolant Indicator Always On

Low Engine Coolant 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 low engine coolant level indicator lamp on the instrument panel cluster (IPC) is controlled by the body control module (BCM) through the low speed GM LAN Serial Data line to the engine control module (ECM). When the engine coolant level switch is closed for 30 seconds or longer indicating low coolant, the BCM will signal the ECM to turn ON the coolant level lamp. The lamp will also illuminate for approximately 3 seconds during the display test at the start of each ignition cycle.

Reference Information
Schematic Reference

Engine Cooling Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Cooling System Description and Operation (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)

DTC Type Definitions

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information

Circuit/System Verification

1. Turn ON the ignition with the engine OFF.
2. Command the instrument cluster indicators ON and OFF with a scan tool.
3. The low coolant indicator lamp should turn ON and OFF on command.
4. 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. Turn ON the ignition with the engine OFF.
2. Verify that the low coolant indicator turns ON and OFF with each command when the instrument cluster indicators are commanded ON and OFF with a scan tool.

• If the low coolant level indicator does NOT turn OFF, test for poor connections at the IPC or a faulty IPC.

3. Ignition ON, disconnect the coolant level switch.

• If the low coolant level indicator turns OFF with the switch disconnected, replace the coolant level switch.
• If the low coolant level indicator does not turn OFF with the switch disconnected, test the signal circuit of the coolant level switch for a short to ground.
• If the signal circuit tests normal, inspect for poor connections at the BCM or a faulty BCM.

Repair Instructions

* Instrument Cluster Replacement (Instrument Cluster Replacement)
* Radiator Surge Tank Replacement (Service and Repair)
* Control Module References (Programming and Relearning)for ECM replacement, setup, and programming

Repair Verification

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