Low Engine Coolant Indicator Always On LH2/LC3
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 | Indicator OFF | Indicator ON | -- | -- |
Ground | -- | Indicator ON | -- | -- |
Circuit/System Description
The low engine coolant level indicator is controlled by the body control module (BCM) through the low speed GM LAN Serial Data line to the engine control module (ECM). The normal state of the engine coolant level switch is closed when in contact with coolant.
Reference Information
Schematic Reference
Connector End View Reference
Cooling System Connector End Views
Description and Operation
Cooling System Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
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.
- Ignition OFF, disconnect the harness connector at the coolant level switch.
- Install a 3A fused jumper wire between the signal circuit terminal and ground.
- Engine running, verify the low coolant indicator turns OFF.
- If all circuits test normal, replace the coolant level switch.
| ⇒ | If the indicator does not turn OFF, test the signal circuit for an open/high resistance. |
| ⇒ | If the indicator turns OFF, test the ground circuit for an open/high resistance. |
Repair Instructions
Repair Verification
Verify that the low coolant indicator is OFF with the engine coolant at the proper level.
Low Engine Coolant Indicator Always On V6
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 engine cooling system contains an engine coolant level switch to alert the driver in the event of a low coolant level. When the engine coolant level in the surge tank falls below a certain level, the coolant level switch opens. When the body control module (BCM) detects an open or a high voltage level on the coolant level indicator control circuit. For at least 10 seconds, it will send a GMLAN message to the driver information center (DIC) requesting display of the low coolant level message. There is approximately a 10-second delay before the BCM sends the GMLAN message to prevent the message from being displayed, due to coolant sloshing in the surge tank. 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
Cooling System Connector End Views
Description and Operation
Cooling System Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
| • | Observe the engine coolant level. The engine coolant level should be within the operating range. Refer to Capacities - Approximate Fluid, and Engine Coolant in the Owner's Manual. |
| • | Ensure that the vehicle has the correct engine coolant with correct concentration and is not old, contaminated, or contains additives. Refer to Recommended Fluids and Lubricants in the Owner's Manual. |
| • | Inspect the cooling system for the following: |
| - | Leaks |
| - | Kinked or pinched hoses, especially at the radiator |
| - | Loose, missing, or damaged radiator air seals or deflectors |
| • | Turn ON the ignition with the engine OFF. |
| Important: The low coolant indicator should be OFF with the engine coolant at the proper level. |
| • | Command the instrument cluster indicators ON and OFF with a scan tool. The low coolant indicator lamp should turn ON and OFF with each command. |
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 ON, test for poor connections at the IPC or a faulty IPC. |
| ⇒ | If the low coolant level indicator turns OFF with the switch disconnected, test the coolant level switch signal circuit for a short to ground. |
| ⇒ | If the low coolant level indicator does not turn OFF with the switch disconnected, replace the coolant level switch. |
| ⇒ | If the signal circuit tests normal, inspect for poor connections at the BCM or a faulty BCM. |
Repair Instructions
Repair Verification
Verify that the low coolant indicator is OFF with the engine coolant at the proper level.
