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
Connector End View Reference
Description and Operation
Cooling System Description and Operation
Electrical Information Reference
DTC Type Definitions
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Turn ON the ignition with the engine OFF.
- Command the instrument cluster indicators ON and OFF with a scan tool.
- The low coolant indicator lamp should turn ON and OFF on command.
- 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.
- Turn ON the ignition with the engine OFF.
- 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.
- Ignition ON, disconnect the coolant level switch.
| ⇒ | If the low coolant level indicator does NOT turn OFF, test for poor connections at the IPC or a faulty IPC. |
| ⇒ | 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
| • | 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.
