The glow plug controller manages power to the glow plugs on Power Stroke and Duramax diesels, and it is often the overlooked half of a hard cold-start problem.
What it does
Glow plugs preheat the combustion chambers for cold starts, and the controller decides when and how long to power them. If the controller fails, one or more plugs may not heat even if the plugs themselves are good, causing hard starts and cold-start smoke.
Signs it is failing
- Hard cold starts and cold-start white smoke
- A glow-plug warning light
- Rough idle until warm
- Multiple plugs not powering
Replacement and what to know
Because the controller and the plugs cause similar symptoms, diagnosis should confirm which has failed before replacing parts. A failed controller is replaced as a unit; if several plugs are also bad, they are often done together. Note that the Cummins uses an intake grid heater instead of glow plugs and a controller.
Frequently asked questions
What does the glow plug controller do?
It manages when and how long the glow plugs are powered to preheat the cylinders for cold starts.
Is it the plugs or the controller?
Both cause similar symptoms. Confirm which has failed before replacing parts.
Do Cummins engines have one?
No. The Cummins uses an intake grid heater rather than glow plugs and a controller.
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