Low Engine Coolant Indicator Always On

Low Engine Coolant Indicator Always On

Diagnostic Instructions

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

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 Data List
* Scan Tool Output Controls

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.
4. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal A and ground.
^ If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test the circuit for a short to ground.

5. Ignition ON, use a 3A fused jumper wire to connect harness terminal A to terminal B.
^ If the low coolant level indicator turns OFF, replace the coolant level switch.
^ If the low coolant level indicator does not turn OFF, test the signal circuit of the coolant switch for an open circuit or high resistance.
^ If the signal circuit test normal, inspect for poor connections at the BCM or a faulty BCM.

Repair Instructions

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

* Surge Tank Replacement
* Refer To Programing and Relearning Programming and Relearning
* Instrument Cluster Replacement

Repair Verification

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