Problems with my 305 TBI to 350 speed denisty TPI swap in my 91 bird.

how can i tell if i have a bad ECM?
i hooked up a SnapOn scanner to the ALDL and it's telling me i have no commincation with the ECM.
i put in all of the info that the scanner needs.it then promps me to turn the key into the run postion.once i do that the scanner screen goes blank for a second then pops back up and says there is no commincation with the ECM.
i checked the grounds going to the ECM and i have good grounds on those pins.i checked to see if i have power going to the ECM.i have over 12 volts going to both of the pins at the ECM.
i tried to pull codes by jumpering A&B at the ALDL.i couldn't do it that way either untill i jumpered A(ground)to a ground.then i could pull codes.i got a code 33 which is a MAP code.i then hooked the scanner back up and it does the same thing but the scanner screen doesn't go blank like before.
the car starts and runs(some times)really rough.

 

What prom are you using in the ecm?

 

a stock 90-92 prom with the VATS deleted from it.

https://www.thirdgen.org/techbb2/sho...hreadid=125771

 

one way to check the ECM is to pull the chip and turn on the ignition. The fans should pop on if they do not it is a good sign your ecm is dead.

 

i have one fan and it's wired to a switch.

 

TTT

 

Bandit If your ecm is bad so is mine. I hooked up a scanner on mine today too. It does the exact same thing. I think is has to do with our dreaded tbi to tpi swap. Someone please post some input on how to fix this........

 

well i'm thinking the ECM bad isn't now.
well long story short the car was running last,running alot better than it has been.and the ECM threw a code.so i'm guessing that my prblem with not being able to access the ECM with a scanner is some how in the wiring.

91bluemetalicRS what knid of problems have you had with your swap?

 

I haven't had too many problems. Speedo didn't work for a while, but I finally got that fixed. still have idle issues and a few more minor things to work out and clean up. Mostly just a wiring nightmare from day one. I am glad I did the swap, just wish I had done a few more swaps before attempting this one.

 

well i drove my car around the block last night
my problem was the MAP sensor wasn't getting enough vacume.i put a 91 plenum on and a new MAP.the 90-92 plenums have a third "nipple" for the MAP vacume source.besides a real bad header leak she felt real strong

 

it appears that you have been busy the past couple of months. Glad to hear its up and running. Wait untill you can drive it without worries of anything going wrong. You will be happy you did it. good luck.

 

If I'm reading your first post right you had to jumper the "A" terminal of the ALDL to ground to get the SES light to flash codes? If that's the case right there's the reason your scan tool won't work. Terminal "A" needs to be grounded somewhere, otherwise the data line has no point of reference and the scanner won't see anything. The ECM has several grounds but the only way the scan tool is grounded is through the ALDL. I'd try tracing the wire from terminal A back to the ECM, sounds like it's either not grounded or broken somewhere.

 

i've jumpered "A" to ground and then tried running the scanner and it still wont chat with the ECM.