TBI pcm problems. Replace?

[Cason]

Has anyone had to replace their pcm? My truck runs great sometimes and then it runs like crap. Backfiring, bucking, dying, sputtering. Then it starts running good again. I hooked a scanner up to it. And it’s reading all over the place

Any info is welcomed. Thanks!

 

[1987 GMC Jimmy]

Does your check engine light come on when you first turn the key on? Have you tried pulling codes with just a paper clip? When you say all over the place, could you elaborate on that? Unless there’s some kind of intermittent ground or something along those lines, ECMs generally work or they don’t.

 

[Charlie]

 

[Cason]

The CEL does come on when I turn the key. The scanner is reading crazy. Temp went from 320 to -40, injector pulse is all over the place too. Everything on the scanner was jumping up and down

 

[1987 GMC Jimmy]

It might be a scanner problem or a serial data/ground issue at the ALDL. I would take a step back and just jump the A and B pins (top right pins) on the ALDL with a paper clip to pull some codes. That might help give you a clue. If it lets you pull codes, and the light is acting like it should be, it’s likely the ECM is okay. Certain circuits within it can fail, and the diagnostic portion will continue to work, but I don’t think it’s that common. What kind of scanner are you using?

 

[Craig 85]

Maybe start by checking all your grounds. I know on my 2010 Denali there have been numerous people that have had major electrical and drive-ability issues with this series of truck. Many have found the main ground cable connector failed at the frame. They have either replaced the cable or added more grounds and resolved their problems.

Worth a try before throwing a bunch of money at it.

 

[4WDKC]

The CEL does come on when I turn the key. The scanner is reading crazy. Temp went from 320 to -40, injector pulse is all over the place too. Everything on the scanner was jumping up and down

a bad temp sensor will tell the ecm to add or remove fuel according to the temp.. disconnect it and see what the scanner does.

 

[Cason]

Ok y’all. I had the pcm replaced today and it runs better. Problem solved

 

[HotRodPC]

Did you by any chance hook your scanner to it and see it it's all over the place to confirm it is for certain fixed and doesn't start running like **** again soon and that the scanner is working properly?