'94 Lumina Z34 won't start

[Wired969]

I had a mechanic check it today and it is not getting spark and he said I need a new ICM... where is this located? He says to go get the part at a wrecking yard and he'll put it on for me, so I need to figure it out. Also, is the ECM and ICM the same thing...because I don't remember exactly which he said. If they're different...which one would prevent starting?

[Schurkey]

I had a mechanic check it today and it is not getting spark and he said I need a new ICM...

Has he tested the ICM or is he just guessing based on "no spark"? There's a dozen things that can cause no-spark.

 

where is this located? He says to go get the part at a wrecking yard and he'll put it on for me, so I need to figure it out.

It's what the coils plug into. Under the exhaust manifold of the front cylinder bank. Bolted to the block. Far as I know, there's no difference between the ICM of a Z34 and the ICM of an ordinary 3.1 of the same year. The Treasure Yard can assist with interchangeability. Good luck, won't be fun unless you find a stripped vehicle missing the radiator and fans; an engine out of the vehicle, or one sitting on a shelf. Available new for under $150, although the used one will probably include the three ignition coils, and that could be a bonus. NAPA p/n ECH TP404 according to a quick search of the NAPA web site.

 

Also, is the ECM and ICM the same thing...because I don't remember exactly which he said. If they're different...which one would prevent starting?

ICM = ignition control module. ECM = engine control module. The ICM is triggered by the ECM. Either one could cause no-start.

Edited July 28, 2012 by Schurkey

[Gunboat]

I had a similar problem,I was driving down the x-way and the car (92 z34) just died on me,come to find out that it had blown the ICM and a coil pack,plus,it had fouled out three plugs in the process,oh yeah,the crankshaft sensor was totally shot,that was the biggest B*tch of all the work that had to be done...

[GTP091]

You can have NAPA test the ICM for you. No point in going to the JY to get a used one if yours is fine. Take yours out and get it tested at Napa and if it's bad then go get one at the JY, get it tested and put it in if it's good. If you can take one out at a JY you can put it back in your car.

 

But before you do that check the ICM fuse in the electrical center under the hood. if it's good test the crankshaft position sensor ( need an ohm meter and someone to turn the engine over , pull the CPS sensor off the ICM it`s the harness on it`s own ). then pull the ICM if the CPS is good. The ICM is a bitch but not as big of a bitch as the CPS. Usually a mechanic will try to change the ICM first as it`s a likely culprit, but not always. He could be guessing and guessing will cost you $.

 

The ECM is the easiest to change but usually a pricey unit except from a JY. I can't remember how to test the ECM, never had to. I have 4 spares and the original is still in my car.

[chriswhewell]

I bought my car when the engine wouldn't start. Traced the problem to a bad ICM. Got a new one for $100, and re-located it and the coils to the inside fender to the left of the coolant reservoir , so it will be easier to troubleshoot in the future. Be sure to check the resistance of old coils if re-using them, since a shorted or high resistance condition can be the cause of a module going bad. Secondary resistance read between output terminals on one of the coils should be between 0.2 and 0.7 ohms, and the primary resistance measured between the contacts inside the two slots on the underside of a coil should be between about 6k and 11k ohms.