93 S10 4.3TBI "Z" 5spd ECM/PROM Questions

[GOLIATHGMC]

This truck is WAY too nice to throw away, anyone who has a CLUE what I am missing here will be my hero.
1993 S10 4dr 4.3 "Z" 5spd 4x4. approx 160k on 1owner (my Dad) truck. Had engine replaced 2500 miles ago with NEW GM crate long block. Out of the blue one morning late last October it nearly died about 2 miles from home - limped back and Snap on MT2500 showed multiple failures, including ECM, PROM, Fuel Pump, O2 sensor, TPS, Temp sender, etc. Scanner also read ERROR message saying it had trouble communicating with the vehicle. Dad took it to local well known shop, and they said it was most likely the ECM. Nearly 6 weeks later, the shop called him and asked him to come and pick it up, and that they could NOT fix it. They had replaced nearly ALL of the sensors, the fuel pump, and several control relays, as well as a comlpete R/Inspection/R of the engine harness. In addition, they swapped in 2 separate NEW ECM's, and one NEW PROM. They charged him about $200 for the parts, and wished him good luck.
I have now hooked it up to a brand new ACTRON scanner, and it also shows both an ECM failure and a PROM failure.
The truck is running in closed loop, and bucks like crazy if you try to drive it. Oddly, it also displays very little in the way of data on either scanner - all while idling close to normal (i.e.-shows NO fuel pump voltage, even though the pump is running and the fuel pressure is fine measured on an independant gage).
Is it possible that something was missed with the replacement ECM's? I doubt they were both Bad, but I am wary that they both could have been wrong.
Anyone with suggestions would REALLY be helpful. I consider myself to be a very competent mechanic, but this one is really trying my diagnostic skills.
George
REBEL Motorsports

[Floyd_ODB]

Engine ground?
ECM ground?
short to voltage causing your ECM to fry?
only things I can think of

[crazycory1]

There are two parts to the ecm. The board and the chip. They might have only changed the board twice seeing that your truck is kind of rare being a 4.3 5 speed.

Look for another whole ecm

www.car-part.com

worth a try.

[dmbrisket 51]

when installing a different pcm, you need to keep your prom, or get one of the same number, proms are not interchangalbe, and the same prom stays with the vehical no matter how many computers go in it

[GOLIATHGMC]

Thanks for your input guys - it comes down to this; both scan tools showed fault with the VCM and the PROM - but replacement of these requires a "reprogramming" by a GM TECH1 tool - and only a dealer has them. This is an OBD1 setup, and part of the reason for the creation of OBD2. The GM service manual talks about reprogramming a new VCM or PROM, but says nothing else about what that means or how to do it. Further investigation on my part led me (kicking & screaming) back to the dealer. I am now awaiting the rape that comes with these scammers. My Dad already got one phone call from them (from a secratary who knew NOTHING) basically preparing him for a LARGE bill. Rest assured this is far from over, and they have already hinted that they are looking at replacing things that are BRAND NEW that I know are not faulty. And they wonder why I hate dealers.
GOLIATHGMC

[RahX]

i would go back and check all your grounds and stuff. problems like this are either easy or a complete pain in the ass. throwing parts at it if its a wiring problem gets you nowhere. and an ecm with a prom doesnt need to be dealer programmed, the prom is the program. think of it like this, that ecm is probably the same one they use for a few different vehicles so its like buying an xbox. your prom chip is made for your truck, your prom is like the game. put your prom in the ecm and it plays 1993 S10 4.3 "Z" 5spd 4x4. the obdII vehicles without proms are the ones that need to be programmed and its not overly hard if you have a techII.