How to Check the GM Ignition Control Module

by Johnathan Cronk
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General Motors, Inc designs and manufactures many different vehicles including trucks, cars and minivans. GM sells their vehicles under a wide range of name brands, including Pontiac, Chevrolet and Buick. GM vehicles are equipped with an ignition control module. The ignition control module is responsible for turning the ignition coil on and off. This process allows spark plugs to light the gasoline vapors at specific times, allowing the GM engine to start once the ignition coil is signaled. If your GM vehicle has a slow or hard start, the ignition control module should be tested with an electrical test light.

Step 1

Open the hood of the GM vehicle. Locate the ignition module. The ignition module is found directly next to the cylinder coil packs. Refer to your GM vehicle repair manual for exact location as it varies slightly by model.

Step 2

Connect the positive test light lead to the ignition module signal wire. You will notice a wire harness on the side of the module; the signal wire is the middle wire of the three. The signal wire runs from the ignition control module to the ignition coil. Clip the negative test light lead to a solid ground such as negative battery terminal.

Step 3

Ask a partner to crank the engine numerous times. The test light should turn on and off as the ignition control module is signaled. If no light is preset, the module is faulty and needs to be replaced.

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