GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    •  Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    •  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

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Coolant Level Switch Signal

Lamp ON

Lamp OFF

--

--

Ground

--

Lamp OFF

--

--

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

Connector End View Reference

Component 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

DTC Type Definitions

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References 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.
  3. If the low coolant level indicator does NOT turn OFF, test for poor connections at the IPC or a faulty IPC.
  4. Ignition ON, disconnect the coolant level switch.
  5. 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
    •  Radiator Surge Tank Replacement
    •  Control Module References for ECM replacement, setup, and programming

Repair Verification

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