How to Test an Ignition Module

What You'll Need
Safety glasses
Vehicle wiring diagram
Digital volt Ohm meter (DVOM)
Test light

The ignition module is responsible for creating the spark that starts your engine, so when your car won’t turn over, testing this part is a good place to begin. You will want to determine whether the ignition module is producing electricity and that the electricity is getting to the spark plugs to get your engine going. With this piece being on both sides of the dashboard, you will need some help with testing. Care is also needed since you are working with electricity, so follow the directions below to complete this task safely and successfully.

Step 1 - Locate Ignition Module

To locate the ignition module, refer to a wiring diagram for your vehicle’s particular make and model. As you might guess, the placement can change based on the type of vehicle, so it is important to have the correct diagram or you will be practically going in blind. You'll want to identify the terminals running in and out of the module once you have found it.

Step 2 - Check Module Current

Ground the negative lead from your DVOM to the vehicle’s metal frame. Then, while your partner turns the key, probe the ignition module’s terminals for current. If there is no current, you will need to replace this part entirely.

Step 3 - Check Spark Plug Current

As mentioned previously, you will also need to be sure that the electricity from the module is getting to the spark plugs as well. Test this by attaching a 12V test light to your spark plug terminals. If the light flickers when the ignition is cranked, you will need to check other components for a solution to your starting problem. If the light does not come on, inspect the wiring to the spark plugs for tell-tale signs like burn marks, fraying, and breaks.

You can also use your DVOM to check for continuity if there are no obvious visual signs of damage. Switch your meter to the Ohms setting and test the wiring again. An infinite reading on your meter means that there is no continuity and your wiring is faulty. Make sure to check all wiring going to and from the ignition module and spark plugs since wires are much easier and cheaper to replace than engine parts.

If your ignition module does need replacement, you can choose to do it yourself if you're confident in your level of experience. For amateur do-it-yourselfers, it may be better to seek professional assistance.