CAUTION: The glow plugs operate on a 7–volt system. DO NOT test the glow plugs with a 12 V source as damage will occur to the glow plug(s).

The Engine Control Module (ECM) monitors various engine sensors. When the ignition key is turned to the ON position, the ECM sends a signal to the glow plug module (relay) to turn on, and cycle, the glow plugs for a pre-determined amount of time, plus illuminate the glow plug light in the instrument panel. Once activated, the element inside of the ceramic core of the glow plug begins to glow. Each glow plug draws approximately 8 amps, for a total system amperage of 32 amps at 22 degrees C (72 degrees F) ambient temperature. If there is a fault with the glow plug system, the ECM will store a fault code.