Diagnostic Aids

WARNING: This page is about a different car, the 2019 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.

This diagnostic uses a comprehensive approach to the diagnosis of the KR33 Auxiliary Heater Coolant Pump Relay and its related circuits. The auxiliary coolant pump relay is a printed circuit board (PCB) relay. The relay is an integral component to the underhood bussed electrical center (UBEC). It cannot be removed and it is not visible.
Much of the diagnosis is performed at the ECM connectors. Great care should be taken to ensure that the correct terminals are tested and the proper test probes are utilized when performing this diagnostic.
The test lamp is used to provide a visual aid to observe the integrity of the KR33 Auxiliary Heater Coolant Pump Relay, the UBEC and the relay control circuit.
Grounding terminal X1-66 activates the powertrain relay, which will supply power through KR33 relay coil and the relay control circuit. Under normal circumstances the test lamp will illuminate with dim intensity due to the load created by the KR33 relay coil. If the test lamp does not illuminate, or illuminates brightly a condition exists in the KR33 relay control circuit or the UBEC.