hi all. im actually a tech myself and i have read through many of the posts on this forum about this code because i have a problem truck im working on right now. i have noticed a lot of people have had the same exact problem that i am having and so i am posting this in hopes that i can find the correct answer or at least some explanation of how the ignition control and fuel injector control function on this vehicle. i am working on a 95 chevy s10 blazer with the 4.3 CPI engine (the one with only 1 injector). i have done many hours of testing on the vehicle and so far this is what i have:

vehicle starts and runs perfectly fine after i clear the p1351 code. if i disconnect the injector and install a noid light to the connector, the noid light flashes normal while cranking but only for the first 2 or 3 seconds. then it stops. and it will not flash again no matter how many times i try to crank the engine over. if i let it sit for a little while (20 minutes or so), it will flash again during cranking, but same thing after 2 or 3 seconds of cranking. so basically something is stopping my injector from firing if i have a longer than normal crank time and will not fire again for some time. (maybe something electronic overheating while cranking?????) also, i did all the testing related to the p1351 code and the only part of the testing that stuck out is on my white wire at the ICM connector i am getting around 5.5 ac volts which is higher than the specified 0.5-4.5 ac volts. but this voltage is coming straight out of the vcm so that is the part i suspected. tried replacing the vcm and same situation. i would also like to add that there is some type of aftermarket alarm system that was installed on this vehicle (looks like a long time ago) and there are wires and switches all over the place. one wire that really sticks out to me is a wire that is spliced directly into the white wire that goes to the ICM. i have already tried testing everything over again with that wire cut off and it did not change anything. i am still getting around 5.5 ac volts from the vcm and my injector still quits if i crank for longer than a couple seconds.

ok so i have a couple different questions. first of all, does anyone have any ideas on what could cause this condition? and also, what is the relation/connection between the fuel injector control circuit and the ignition control circuit? do they both run off the same sensor? is there something that could be overheating during cranking that would shut the injector down until that component cools back down? what is it that decides the ac voltage from the vcm to the icm (could there be extra voltage coming from the input to the vcm that affects the output from the vcm to the icm?) i really think this could help a lot of people figure this problem out so please let me know what you think. i will update tomorrow anything else i find out while working on the truck. thanks in advance