91 pcm emergency help

[tuck817]

so i just bought a 91 2door exp i then got a good deal on transmission rebuild now not getting power to overdrive or torque converter i pulled pcm and its part # f07f-12a650-va which is showing to be from a manual trans i need to know if i can just buy one for an auto trans or what please help goin to junk yard tmmrw

 

[Maniak]

Did you swap the manual to an automatic? The reason I ask is that there is a wire harness for the auto trans that runs up from the trans up to the drivers fender. It runs near the exhaust if the factory "clip" is gone so watch that.. If you don't have that harness you have to get more than just the ecm.

Anyway, My guess is they had an ECM issue and just threw in a computer they could find to make it start/run. If that is the case then yes you can just grab the correct computer..

You need to check if you have what looks like a MAP sensor on the firewall on the passenger side. If you do you must get a pcm from a 1991. If you don't you can "probably" get one from a 1991 or a 1992 since that means you have a later 1991 model.

~Mark

 

[tuck817]

what would happen if it has been switched from manual to auto and didnt have the harness when i put the pcm on would it catch on fire or would it just not work

 

[Maniak]

It would just not work (trans shifting into OD and lockup) and would should throw a CEL saying the solenoids weren't found (eventually it would throw the code).

~Mark

 

[tuck817]

do u know wich pcm i would get i am thinking that it was always an auto cause i think the window motors shorted would that cause a pcm to go bad

 

[Maniak]

Anything is possible, but I'm almost 100% sure that the window motor/control for window does not go through the ECM at all. They just go through a big fuse under the hood and are on switched power (via the ignition switch).

I don't have a hollinger interchange so I can't tell you what ECM you "should" have.

I'd look for the BAP sensor on your firewall (upper passenger side-ish). If you have that, you need to find an ECM out of an explorer that has the auto trans AND that BAP sensor. If you don't have the BAP then you "should" be able to grab one from a 91 or 92 with a auto trans.

~Mark

 

[tuck817]

thanks does it have to be out of a 4x4 or no i just payed good money to rebuild that trans i hope this works the guy at the trans shop wont warranty the build if it doesnt shift right

 

[Maniak]

If you have 4x4, yes, get it out of a 4x4. I've never done the swap, but IIRC, MrQ has done the 2wd to 4x4 swap and I'm pretty sure he did have to swap ECM's.

~Mark

 

[tuck817]

well i pulled a f07f-12a650-abb at the junk yard for $35 put it in shifts better no idle issues and got the warranty now to clean auto hubs thanks for the help