2012 silverado, e38+t42+4l80... help

[mattkguns]

Screenshot 2024-11-21 154803.png

i dont care about being right, btw, im just confused.

[blindsquirrel]

What is the Output Speed Sensor for, then? Why is there an ISS & OSS wired direct to the TCM, and that extra 4WD-only thing they're calling 'VSS'?

[gtstorey]

My wild-ass guess is that that speed is just sent directly to the Instrument Cluster so the hi-lo of the transfer case is doesn't matterfor showing vehicle speed.

Did this ECM start out in a 4WD?

[mattkguns]

re: Blind squirrel. what you said before about the oss wired directly to the tcm on the t43. that means my truck as it was built had iss, oss, and post transfer case vss.
looking at the 4l60 builds, they have iss, no oss, and they use the post transfer case vss with the t42. im also noticing a replicated tos hardwired from the t42 to the e38 in the diagrams. some of the options in the vcm editor lead me to believe this might be done via can.

Screenshot 2024-11-21 174219.png

then again i could just be seeing what i want to see

[mattkguns]

re: gtstorey
yep, the whole project is being done in the original truck, 6l80+t43 swapped out for 4l80+t42

[mattkguns]

I think were finally getting somewhere

i was getting a p0716 iss code along with max line pressure, but iss rpm looked like it was solid, so i tried disabling the p0717 diag which seems to have done the trick

also getting a p2160, but it doesnt seem to be causing other issues yet. im assuming its cause the vss sensor has now been hijacked from the ecm for the TCM. i imagine resolving this will require running another wire from the tcm to the ecm for the replicated tos.

shifts are very stout at part throttle for now, but i havent started messing with the shift times and pressures yet.

i still havent messed with changing my e38 OS yet. its been working well enough to test out the tcm/4l80 so far but id eventually like it to all be right.
is the accepted answer.

if it helps at all ive attached the tune

MineW4L60OS v3.0.hpt