If the light doesn’t light up, the glow plug is bad and should be replaced.Įasier is to use a professional glow plug tester device. Then disconnect the wires from each of your glow plugs and touch the probe of the test light to the terminal of the glow plug itself (not the wiring harness). To test your glow plugs, simply connect a 12-volt test light to the positive battery terminal. The easiest is to check your glow plugs before testing your glow plug control module. How can you test your glow plug control module?įirst things first, is it a problem with your glow plugs or your glow plug control module? Poor engine power – after a difficult start, bad glow plugs will make it difficult for your car to run properly, due to improper combustion which reduces power and efficiency.However, this can also be a symptom of a problem in the fuel system or battery. Hard to start – this could mean the engine is slow to start in warm weather or fails to start in cold weather.White exhaust smoke – a defective glow plug will cause diesel to leak into the exhaust where it burns.

In addition to watching out for the glow plug light on your dashboard, here are some common symptoms of a defective glow plug or glow plug control module: However, if two of three go bad or the control module itself malfunctions, you’ll quickly find it difficult to start the engine. This means that you might not notice when a single glow plug goes bad as this only affects one cylinder in your engine. What are the symptoms of a defective glow plug control module?Ī diesel engine has one glow plug control module which controls the glow plugs. This would result in increased exhaust emissions. However, a glow plug control module is still essential, as without it controlling your glow plugs, the compression temperature might not be high enough to ensure proper ignition of the injected fuel in a cold diesel engine. This process is helped by the increase in temperature of the intake air during compression and the relatively low ignition temperature of diesel.

The glow plug remains on during the pre-heating phase to ensure correct combustion of the fuel and reduce the environmental impact of your car.

The injected fuel mixes with the compressed air, evaporates and starts combustion almost simultaneously, even when the engine is cold.

The fuel injector spray directs fuel onto the hot tip of the glow plug.

The heating element in the glow plug is electrified so it heats up and emits visible light (hence the name).

The glow plug control module determines the timing and electric current required by the glow plugs based on input from the Engine Control Unit.When you start up a diesel-powered vehicle, the following actions happen: The current to the glow plugs is turned on during the pre-heating to warm up the engine, stand-by time when the engine should be started, and post-heating to meet increasingly strict exhaust gas standards and optimisation of combustion processes. This includes when to switch the current for the glow plugs on and off, and how much current is required as this will differ depending on the starting temperature of the engine. Located on the engine and with a direct connection to the engine control unit, the control module uses a microprocessor to analyse input from the engine control unit to determine information related to the working of the glow plugs. But how is the overall operation of your glow plugs monitored and controlled? This is done by a glow plug control module. As you already know, a glow plug is a heating device in each cylinder of a diesel engine that helps the engine to start.

Mazda 3 glow shift