After Boil Coolant Pump Malfunction

After Boil Coolant Pump Malfunction

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.

Circuit/System Description

The auxiliary coolant pump and cooling fan system provides a measure of prevention against fuel vaporization due to excessive engine temperatures. The engine control module (ECM) commands the auxiliary or after boil coolant pump ON when the engine coolant temperature exceeds a calibrated value after engine shut down. The ECM applies ground to the coil side of the auxiliary pump circuit board (PCB) relay. This energizes the coil and applies voltage directly to the pump motor through the switch side of the relay.

Reference Information

Description and Operation

Cooling System Description and Operation

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P2600, P2602, or P2603 is not set.
2. If any auxiliary coolant pump DTC is set, repair the DTC first. Refer to DTC P2600-P2603.
3. Ignition ON, command the Aux. Coolant Pump Relay ON and OFF with a scan tool. Verify that the G8 auxiliary coolant pump turns ON and OFF when changing between the commanded states.
4. If the G8 pump does not activate, refer to After Boil Coolant Pump Inoperative. After Boil Coolant Pump Inoperative

Circuit/System Testing

1. Test for a blockage or restriction in the G8 auxiliary coolant pump lines and hoses.
2. Test the G8 pump coolant passage for a blockage or a restriction.
3. Test the G8 pump impeller for a seized or binding condition.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

- Auxiliary Water Pump Replacement (LAU)
- Auxiliary Water Pump Inlet Hose Replacement (LAU)
- Auxiliary Water Pump Outlet Hose Replacement (LAU)