Diesel engines operate by pulling air into each cylinder, compressing it until it gets extremely hot, and then injecting fuel which then ignites. Glow plugs play an essential part in this process, and have three main jobs:

• Before starting the engine, they’re used to pre-heat the cylinder to ensure the air is hot enough for combustion.
• They sustain cylinder temperature both during and after starting the engine.
• The glow plugs may remain operational for a short period of time after the engine starts to reduce emissions (not all engines do this).

This functionality is especially critical in colder weather, when the heat from the compression escapes into the cold cylinder walls. Without the glow plugs, your engine may not be able to start at all, and even if it does start, you’ll likely deal with rough operation and inefficiency.

What does the glow plug module control

Glow plugs need to receive an immense amount of power as they heat up to 1800-2700 degrees Fahrenheit in a matter of seconds. They receive this power from the glow plug control module (GPCM). The GPCM receives communication from the ECM to know when to turn the glow plugs on and off. Depending on the specific engine and glow plug controller, it may also dynamically adjust the amount of power that the glow plugs receive to ensure the ideal temperature is maintained.

What are the symptoms of a bad glow plug control module

Glow plug control modules are prone to failure. This failure can look a bit different based on which vehicle and engine you have, but there are a few things that commonly indicate a faulty module.

• A complete failure of your glow plug system. If none of your glow plugs are working, it’s a strong indication of a module fault.
• Loss of power to a single glow plug. If your engine seems to be running rough right after starting, check the individual outputs from the glow plug controller to each plug to ensure that there is proper output voltage. If one or more outputs isn’t working, the controller is at fault. If the outputs are all acceptable, you likely have a failed glow plug. In addition to complete and partial power loss, you may also have diagnostic trouble codes.

Glow Plug Controller Fault Codes

GPCM failure is usually indicated by starting issues, rough operation, and inefficiency. However, when troubleshooting your vehicle, it’s helpful to more accurately pinpoint the problem by scanning for codes. In the case of glow plug controllers, the most common trouble codes include P0670 (Glow Plug Control Module Circuit Open), or an open driver error. The specific codes can vary greatly based on the vehicle, so it’s important to research the exact meaning of the code to verify that it relates to the glow plug controller.

Glow Plug Control Module Repair and Replacement

Once you’ve properly diagnosed the glow plug controller as the failure, it’s important to understand the options for fixing it. In some cases, there are replacement options available depending on the year, make, and model of your vehicle. However, once the manufacturer no longer supports the part, you’re left looking for used modules or aftermarket versions. We recommend against using aftermarket modules, as many users report that they are short-lived, and can actually cause more issues and errors for your vehicle due to incompatibility. Sometimes the best option to get your vehicle back on the road quickly without breaking the bank is to repair your existing module.

At Circuit Board Medics we repair glow plug control modules to function better than new. One of the main benefits of repairing instead of replacing is that you don’t have to worry about programming and incompatibility issues. In addition, the repair ensures that the root cause of the failure is addressed, so you can avoid future failures. For certain modules such as the LLY glow plug controller, we also offer an exchange service – simply place your order and we’ll ship out a replacement on the same day.

If you’re in need of fast GPCM repair, you can browse our repair options here. If you have any more questions or would like some help troubleshooting your vehicle, you can give us a call at (800) 547-2049. We look forward to serving you!