I recently converted my 93 to a 94 type PCM. I have had a code 42 ever since the swap. The car runs and drives fine, but the check engine light is almost always on. I have tried a differant PCM and a differant ignition module. Every thing I read about this code says that if the motor runs with this code it is intermittent and can't find anything on how to fix an intermittent code. I have tested the wire that runs from the PCM to the ign. module and it seems to be fine. Is the Ign. module differant for the 94 PCM or is it the same as the 93? I'm stuck on this one...any ideas???

 

I hate to make a bad situation worse, but, you have another problem. A 42 code will NOT light the SES. You need to scan it again.

If you feel the 42 is intermittent, the first thing you want to check is how tight the connectors are between the PCM and the ICM. Also, if you have a wiring issue between the coil and ICM that can also give you a 42.

Check the black wire on the ICM for a good ground, the pink/black wire and the white/black wire for 12 volts DC and last the white wire on the ICM for AC. With the meter set to AC crank the engine and check the white wire for voltage between 1 and 4 VAC.