My car's service manual shows this for the ignition coils:

ignition coil

What is the ICM? Related to https://mechanics.stackexchange.com/a/2850/31, is there a way to check the coils to see if they are working correctly?

2003 Honda Civic EX D17A2 1.7L SOHC engine

  • The ICM is the Ignition Control Module. In order to tell you how to test this, we'd need to know what vehicle it belongs to ... Is this for a civic? Need some info from you so we can help :D Jan 6, 2015 at 1:26
  • Aye. It should just be automatically added when we post things.
    – endolith
    Jan 6, 2015 at 1:32
  • 1
    I should have mentioned before. The easiest test for a coil is to trade the position of the coil and see if the problem follows. You should have four identical coils. If cyl 2 is having an issue, trade it with the one on cyl 4 and see if the issue now exists on cyl 4. If it moves you found it. If it goes away, it's some thing else. If it stays at cyl 2, there's an issue in the wiring most likely. Jan 6, 2015 at 2:16

1 Answer 1


Honda Coil Over Plug setups have three wires. As mentioned they have an internal Ignition Control Module. Pins 1 & 2 are power and ground while pin 3 is the control signal from the Electronic Control Module.

You can test coil resistance with a multimeter.
How to Test an Ignition Coil with a Multimeter

You can also check the primary coil with a digital storage oscilloscope and a low amp inductance probe by observing the primary coil waveform.

This is known good ignition coil waveform from an 09 Accord 2.4 that uses the same style ignition coil.

enter image description here

Generally when observing waveforms problems on the primary coil will affect the secondary coil and vice versa.

As paulster2 mentioned you could also check ignition coil performance with a misfire code by swapping the suspect ignition coil, resetting codes and waiting for another code to show up.

Or by again swapping the suspect ignition coil and observing misfire counters with a scan tool.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .