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 Module
The Glow Plug Module is connected to a fused B(+) circuit and receives a path to ground at all times through the engine wiring harness. These connections allow it to remain functional regardless of the Electronic Ignition Switch (EIS) position. When the Engine Control Module (ECM) receives the On and Ignition Run signals from the EIS, it will send a signal through the LIN bus to actuate the Glow Plug Module for a period of time that depends on ambient air and engine coolant temperature.
The Glow Plug Module utilizes integrated relays and microprocessors to actuate the Glow Plugs based on input from the ECM. The Glow Plug Module has on-board diagnostic functions that will set powertrain DTCs, which will be transmitted to the ECM through the LIN bus. Because the Glow Plug Module uses microprocessors to control battery voltage to the Glow Plugs, conventional diagnostic methods will not always prove conclusive when diagnosing problems with the Glow Plug Module and related circuits. For proper diagnosis of the Glow Plug Module, the LIN data bus or electronic communication related to Glow Plug Module operation, a diagnostic scan tool is required. See OPERATION .
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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.