HCFX

Wondering if some guru's can help me out. Have a 5.3 in a 71 GMC pickup. Was originally a P01 4L60 PCM I had tuned and revised by a local reputable tuner but long story short he stopped communication after some disagreements in fuel trim diag early on. So I guess I'm on my own now. The truck runs, drives beautiful and I'm generally happy with the tune for now.

Did the proper wiring mods to swap to the 4L80. Double, triple checked my work. When the ISS is plugged in I get a P1860 TCC PWM Electrical code and as far as I can tell, no converter lockup. When it's unplugged I get an ISS Circuit code, lockup at 40mph, unlock at throttle lift and extremely hard shifts, so the PCM is seeing the ISS, the lockup solenoid works and the pcm is at least partially segment swapped. Problem is when the ISS is plugged in I can't get it to lock up, at least not at a reasonable speed (haven't had it up over 65mph yet). I believe it's tune related, hoping someone can help point me in the right direction?

TIA!

FranksCustomTrans

The code is an electrical code meaning either your wiring is not properly does for the swap or the segment swap is wrong or incomplete.
I would verify the wiring first, THEN SEGMENT SWAP, You will likely get more help with the segment stuff in the tuining area of the forum.
But the issue is electrical or tuning in nature. Personally with that particular code I think the segment swap is wrong or incomplete.

HCFX

I agree. I checked the wiring again last night and I just don't see how there's a way it can be wrong especially considering the converter does lock up when that sensor is unplugged. Unplugging the ISS must put the trans into some kind of default mode.

I'll check over on the tuning side. Maybe I can upload the tune for somebody to take a look at. I could see the tune being the common denominator considering the issues I've dealt with to date.