So I got this real big issue of my truck not running and I dont have mch knowledge on these computer issues. I bought a ECM of the same numbers as the original ECM in my truck (P56040975), but the truck still doesn't run.. But it runs with a ECM from a 1997 truck with same engine (but with the ECM from the 97 it misfires like crazy at 3000 rpm and bogs and misfiring while tryin to drive and runs rich) soo why doesn't the ECM with the matching numbers still not run my truck? Does it need to be flashed?

 

What's missing when it won't run? Spark, or fuel? Might be a marginal sensor that the 96 PCMs can't tolerate, but, the 97 is more forgiving..... even though it doesn't run worth squat.

 

With the ECM from the 96 in it, it has fuel and spark, I have tested both of those (Brand new fuel pump not even a month old, and Spark tested the coil and plugs) . I just think I need to flash the ECM from the 96 or 97, but I don't no what it requires or what "flashing" even does. I think this cause with the original OEM ECM that was in my truck has a sticker on the front that says it was flashed in 1996 to a new ECM number (P56040975) when the old number was (P56040892). Could flashing it fix my problem?

 

If you have spark, and fuel... it should run. Have you check fuel pressure? Are you getting injector pulse?

I seriously doubt flashing the PCM would fix anything....

 

Would these be a ecm issue? I meen I dont see a reason why this would be an engine problem (cap/rotor, injectors) since it runs and idles with the 97 ECM and will not run with neither 96 OEM one or same matching 96 ECM I just bought. Could jumped timing be a cause? Since this all started with the fuel pump goin out.

 

not sure how the timing would jump on these trucks because the ignition timing is controled but the ecm not the distibutor. the dizzy controls fuel injector timing not ignition so dont turn it, if u do u may not get it started again cuz it ultimately needs to be set with a computer. are you sure the computer u bought is even programmed or was it a blank that needs to be flashed?

 

If it idles smooth, it's not a timing issue. Probably have a bum sensor somewhere, that the 97 pcm is more tolerant of. Can you get your hands on a scanner that will show real time data?

 

No I dont think the 96 ECM I just bought has been, pretty sure it still synced with the old truck it came out of. And no I do not have a scanner unfortunalty , but ima get the check engine to flash the codes at me and see what it says.

 

makes you wonder if the 96 ecm u got was the same engine...

 

The ECM number I have (56040975) is only for my year, engine and model truck and I checked for codes on both 96 ECM and they both only gave me fault code #32 (which says its EGR solenoid circuit short or open) dont think that would make my truck not run.