Audi A3 Glow Plug Control Module Replacement Cost

Diesel engines are a type of internal combustion engines (ICE) which operate slightly different than the normal gasoline engines that most are accustomed to. Instead of sing a spark to ignite fuel, like gasoline ICEs, they use high pressures and heat to ignite fuel. However, when a diesel engine is first started, there is no heat present, so diesel fuel has no way to ignite. Enter to glow plug. The glow plug gets its name because it becomes so electrically heated that it glows red. This is only needed when the engine is cold, and when the engine reaches a certain temperature, the glow plug control module turns them off.

When the ignition switch is turned from off to start, the glow plug control module does a few things. It prevents the engine from cranking, turns the glow plugs on, lights up a warning lamp that instructs the driver to wait, and finally, shuts down the warning and allows the driver to start the engine, or starts the engine itself. This system prevents excessive emissions, carbon build up, long cranking time which drains batteries, and misfires when starting the diesel engine. Also, this control module can notify the driver that a glow plug has failed.

A faulty glow plug control module will generally lead to a diesel engine that fails to start, fails to start properly, or runs poorly once started. The warning for the driver to wait may not come on, or may stay on indefinitely, which would either prevent the engine from cranking or allow the engine to crank at any time. Also, the glow plugs could be heated to the incorrect temperature, not heated at all, or never turned off. This could cause pre-ignition issues, misfires at startup or failure to start. In general, the only time a glow plug control module should affect engine performance is before, during, or in the few minutes following a cold-start.