An ignition control module takes the signal from the pickup coil or hall-effect sensor and triggers the coil based on that signal. Some modules also trigger injectors and control timing as well.
Check for power and ground at the module with your test light. Refer to your wiring diagram to determine which wire is power, and which is ground. To test for power, clip your test light lead to the negative battery terminal and probe the power wire. If the light comes on, power is present. To test for ground, clip the test light lead to the positive battery terminal and probe the ground wire. If the test light comes on, the ground is good. If no power is present, check the fuses. If no ground is present, check for a loose ground cable connection.
Test the trigger signal coming from the pickup coil or hall-effect device with the DVOM. With a partner cranking the engine, look for a voltage signal with the positive lead of the DVOM while the negative lead is attached to the good ground. No signal means a bad pickup coil or hall-effect device.
The final test is the coil signal. Test for power on the positive side of the coil with the key on. Then test for flashing power on the negative side while the engine is cranking. If this is present, the module is good. If not, it is bad.
Things you need
- 12-volt test light
- Digital volt/ohm meter (DVOM)
- Ignition system wiring diagram