BadAndy

OK, I had a 2002 Fbody LS1 pull out with a 4l60e. I let my good friend have it to use in his little cruiser. He's got a Cutlass that he's swapped the drivetrain and electronics from a 98 or 99 Tahoe into. Engine, trans, and PCM. Trans was garbage so I gave him mine. After he did what he needed to do to make it fit, it runs and drives, but doesn't shift right and throws codes. As far as the shifting goes, he just said it wants to wind out every gear under normal easy driving.He's going to pull teh codes and send them to me later. I would have thought it would be a direct swap, but I'm often wrong. What are we missing here?

thor68372rockon

Not sure if this is correct on this year, maybe somebody with knowledge of the correct years this worked on can chime in & correct me. Did you remove both battery cables, touch them together to clear PCM codes for a fresh start? I think you touch them together for 1-2 minutes & that clears all the codes & puts it back to a clean slate. then drive it for a while & the PCM will relearn how it's supposed to act. heard it will run like sh@t for a while until the relearn process is complete. Like i said though, don't know if it's late model or early model this works on. Hope it does help.

P.S. I think you let it idle for 2-5 min., then put in drive at idle for 2-5 min. first, then take it for a drive & let it relearn.

mrvedit

Is a '98 or '99 Tahoe an LS or LT engine? (Sorry I don't know GM trucks and SUVs.)
If an LS engine, then it should have been fine as LS-style 4L60E from '98 to '05 are completely interchangeable and '06-'08 with the ISS (Input Speed Sensor) will work perfectly with any LS1 PCM.

I would connect a pressure gauge to see what the line pressure is and confirm that it goes up near the 200 psi range when you blip the throttle. Sound like the line pressure is extremely low.