okayy i got a 94 z28 cc503 cam. 2800 stall. roller rockers, ls7 lifters, ram air.. etc.. however i have a vented opti on it....run fine for years rah rah rah it stumbled yesterday morning... gas gauge was a lil low.... went to the store got gas.. put it in.. tried it about 3 times.. no crank then it did.... drove it away like a hour cut off 5 6 times everything good.. came home bitch aint cranked up since... set EGR codes which where obvisoulsy set when i deleted the EGR with the cam swap and one other code! 42? WTF EST grounded....

ive traded out ICM eliminated that
Coils eliminated that
Traced fuses eliminated that

any ways to diagnose this again.. car will not start to save your life?
fuel pump is working.. just no fire out the plugs anywhere! THANKS

 

DTC 42 = Ignition Control (IC) circuit (shorted or grounded circuit)

You need to check the voltage on the white wire that runs from the PCM to terminal B of the IC module. Code sets when the voltage drops below 0.5V. Should be in the range of 1 - 4 V.

Shoebox also has a guide to verifying that the signal to fire the coil is getting to the ICM.

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

 

Imho If your battery is in the stock location, look at the ground wire and the battery cable to the negative terminal; wiggle them around hard and see if it starts or tries to with more authority. You may need a wire brush and some baking soda disolved in water if the negative post is badly corroded. If the connection seems improved then clean the battery posts and lubricate to prevent re-occurence. The connection directly down from the battery may just be loose. It can work lose over time. This is the place where the battery power connects up with the line to the starter. Sometimes this gets loose. Finally, the stock ground wire to the block can degrade from years of use.