Low Engine Coolant Indicator Always On

Low Engine Coolant Indicator Always On

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (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 circuit. When the engine coolant level switch is open for 30 seconds or longer indicating low coolant, the BCM will signal the IPC to turn ON the Low Coolant Indicator 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 (Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Cooling System Description and Operation (Cooling System Description and Operation)
Electrical Information Reference

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

Scan Tool Reference

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

Circuit/System Verification

1. Ignition OFF, verify the radiator surge tank is filled to the correct level, with engine coolant.
2. Ignition ON, observe the scan tool coolant level parameter. The parameter should display OK
3. Command the instrument cluster indicators ON and OFF with a scan tool. The low coolant indicator lamp should turn ON and OFF as commanded. Refer to Cooling System Description and Operation (Cooling System Description and Operation).
4. The low coolant indicator should be OFF with the engine coolant at the correct level.

Circuit/System Testing

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

1. Ignition OFF, disconnect the harness connector at the B33 coolant level switch.
2. Test for less than 5 ohm between the ground circuit terminal B and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool coolant level switch parameter reads LOW.

• If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the K9 BCM.

4. Install a 3 A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B. Verify the scan tool coolant level parameter displays OK.

• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.

5. If all circuits test normal, test or replace the B33 coolant level switch.

Component Testing

1. Ignition OFF, disconnect the harness connector at the B33 coolant level switch.
2. Test for infinite resistance between the signal terminal A and the ground circuit terminal B with the switch in the open position.

• If not the specified value, replace the B33 switch.

3. Test for less than 5 ohm between the signal terminal A and the ground circuit terminal B with the switch in the closed position.

• If greater than the specified range, replace the B33 switch.

Repair Instructions

* Radiator Surge Tank Replacement (Radiator Surge Tank Replacement)
* 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 correct level.