93 vett LT1, starts then dies after a few min. code DTC42 appears. Have replaced the opti (100,00+miles), plug wires, plugs, water pump, still does same thing. What is DTC42? Factory man says; "Ignition control circuit (grounded circuit)" does that mean something wrong in the ground from the ICM or anywhere in the whole ignition control circuit? Or does it mean some wire is grounded that shouldn't be. The man says step 1 "clear DRC, crank engine for 15 sec, does DTC42 set?" It doesn't, comes on only after car starts then dies so this is supposed to be "intermittent"? Any help appreciated.

 

This is for a '95 from shoebox site, the DTC 42 says the pulse from the PCM to the ICM that fires the coil is being held to ground. Could be a bad ICM messing up the signal from the pCM when it gets hot.

http://shbox.com/1/4th_gen_tech2.html#opti_test and http://shbox.com/1/95_ign_system_schematic.jpg

 

I was wondering about the ICM it gets very hot, almost too hot to touch and when it gets hot thats when the car dies, if i let it cool it will almost always start then die shortly after it starts. I tested the ICM at O'Rileys, it showed good but it never got that hot even though we cycled it several times, I have a new one ordered. If it was a short somewhere else it seems like it would be more erratic, plus I jiggled all the wires I could in the vicinity of the coil and ICM and it never died until the ICM heated up. Any thoughts. thanks for the reply, I really appreciate it.

 

You can space the ICM off the head to help it run a bit cooler:

http://shbox.com/1/4th_gen_tech2.html#ICM_cooling

 

Problem solved! It was the connector at the ICM. I removed the ICM from the head and strapped it to the power steering resivor hoping that would keep it cooler but the car still died and showed code 42. So I started it again and then grabbed the ICM and it wiring and moved it back and forth, every time I did the motor would stumble then it died. So I tightened the pins in the connector by bending them slightly and presto it was fixed. I moved the ICM and all the wires still it kept running, then I test drove it for about 30 min, no problem. Thanks to every one for all the help.