Module, Glow Plug, 3.0L Diesel: Operation

WARNING: This page is about a different car, the 2018 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

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 Powertrain Control Module (PCM) 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 microcontrollers to actuate the Glow Plugs based on input from the PCM. The Glow Plug Module has on-board diagnostic functions that will set powertrain DTCs, which will be transmitted to the PCM through the LIN bus. Because the Glow Plug Module uses microcontrollers 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. Refer to COMMUNICATION, OPERATION .