Ecm is driving me nuts....
 

Soooooooooo. I have an 2002 4.3 s10 i was driving to work i pulled in and the truck died on me turns out the ecm b fuse popped no biggie, through another in there and it fired up and i drove home where it died again as i was almost in my driveway. This time however it would instantly blow the fuse upon replacement i was told it was the ecm so i bought a new one had it flashed to my truck specs and proceded to install, as soon as i plugged the ecm back in it blew the ecm b fuse once again. Had the new ecm tested again it showed perfect and i couldnt find a short between ecm b fuse holder and the bottom ecm plug.... if anyone has any insight it would be much appreciated i just wanna drivey truck again

There are two separate wires running to the PCM from ECM fuse B. See attached schematic. Did you check the full length of both of them? Sometimes wiring harnesses get mis-placed and burnt on hot passenger side exhaust manifold or A.I.R check valve tube. Good luck

Yes! I have checked each wire with a multi meter and visually inspected them. everything points to the ecm or fuse box and i know the ecm is good, and have 0 idea on how to go about testing the fuse box

Disconnect ECM. Take fuse out. Check resistance of circuit between between (non-hot) fuse terminal and battery ground. Should read no continuity (not shorted to ground). Now plug in fuse but not the ECM. Does the fuse blow? If not, check the two pins in the schematic at the ECM connector (unplugged) for 12V. If OK, plug in the ECM. If the fuse blows, the ECM is bad.

You should have a 20A fuse for ECM B.

If you still have a problem, know that the six wiring harness connectors unplug from the back of the underhood fuse block once you take it loose.

Also check G103 (#7) in the attachment. This is the ground for the PCM. Sometimes people who take off cylinder heads or remove engines think this is an optional ground or don't get it tight. Yes, it is difficult.

Got home today and checked ecm wiring some more, all wires act as they should i figured ecm was bad so i made an inline fuse out of a 20 amp fuse and 2 wires tied the two orange 12v wires to it and attempted to connect it to the hot post on battery immediatly popping the 20 amp fuse. This is where it gets interesting i placed the suspected burnt ecm into my other identical truck and it ran just fine no codes no fuses i drove it 40 miles and not even a hiccup im going to check the ground you mentioned tomorrow and see what it shows and ill attempt to post results

Did you do the tests that I outlined? If so what was the result of each?

So i did as you said disconnected ecm end unfused the ecmb tested outgoing non hot and it did showed ol on the continuity i plugged the ecm back in and tested it shows 10.7 ohms i also checked the ground you mentioned and the result was .03 ohms. I paid for a new ecm a couple days ago and it came in while i was at work i plugged it in and repeated steps above and it still pops the fuse immediatly which make me beleive 100% that ima lost pup on this one

So i did as you said disconnected ecm end unfused the ecmb tested outgoing non hot and it did showed ol on the continuity i plugged the ecm back in and tested it shows 10.7 ohms i also checked the ground you mentioned and the result was .03 ohms. I paid for a new ecm a couple days ago and it came in while i was at work i plugged it in and repeated steps above and it still pops the fuse immediatly which make me beleive 100% that ima lost pup on this one

Hmmm - unless there is something outgoing on the ECM that takes it's power from there (you have checked everything on the power incoming to ECM and the ECM itself). I know that the ECM drives injectors (probably drives/powers a lot of things) but I thought the ECM would shut down before blowing fuses. Maybe disconnect the connector from the intake top and see if that fixes the fuse blowing? Look over the other parts of the engine wiring harness for burnt spots on the plastic cover. This is just a guess, though. I hate to deal in guessing and pure speculation, but that's all I have for you at this point. I can say from experience that the wiring to injectors coming out of the ECM goes right past the front of the passenger exhaust manifold and the A.I.R. manifold tube. Mine is a 2001 - not sure if 2002 still had the A.I.R. Manifold. Mine was melted there after an engine replacement. Harness was supposed to be in a clip.

Let me know if it has something to do with the injectors or possibly elsewhere in wiring harness. I might be able to subsequently search a bit and find other things to check if necessary. Not giving up just yet.