Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Glow Plug Controller
The glow plug controller provides glow plug operation after starting a cold engine. This after-start operation is initiated when the ignition switch is returned to "RUN" from the "START" position. A faulty controller may result in excessive White smoke and/or poor idle quality immediately after starting. The following procedure checks for proper operation of controller circuit. Ensure coolant temperature is below 80°F (27°C) before beginning test.
- Place ignition switch in "RUN" position and allow glow plugs to cycle. After 2 minutes, crank engine for one second. It is NOT important that the engine starts. Return ignition switch to "RUN" position. Glow plugs should cycle on at least once.
- If glow plugs do not cycle, disconnect controller connector (controller is located on top, rear of valve cover). Connect 12-volt test light between Purple/White wire terminal of harness connector (terminal "B") and ground ("G" van and "R/V" and "P" series, use solid Purple wire). With ignition switch in "RUN" position, test light should be off. Test light should glow when engine is cranked. See Figure.
- If test light does not operate as specified, repair short or open in engine harness Purple/White (Purple) wire. If test light operates properly but glow plugs did not cycle, replace controller.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.