TPI in limp mode

[Z1LE]

I finished my auto to T56 swap a few months ago in my 91 Z28 and have yet to wire up the VSS converter. When I started the car the fan came on immediately and the Check Engine light came on. They both run solid from turn of key and stay on. Was told its in limp mode as I couldn't connect the ALDL to pull codes. Was told to change the ECM but no change. Was wondering if the VSS not being connected can cause this? How likely is it that my PROM is bad? Can anyone point me in a direction of how to start?

thanks
Kris

[RobertISaar]

lack of VSS wouldn't do it....

since you swapped ECMs already, i'd say your PROM(or possibly entire MEMCAL) is probably the issue.

[Z1LE]

Thanks. Now to find a memcal.

[EagleMark]

Getting into Limp Home Mode is pretty hard, but it points to chip/memcal as Robert said. I've yet to see a chip or Memcal go bad without human intervention and even then it's hard.

VSS won't cause it, LHM is total failure backup. So back step what you did? Any pins in harness bad or bent, wiring, short. The Memcal didn't just go bad, something happened and it's probably fixable.

[Z1LE]

Yes I agree. I did do something that was a silly mistake being rushed and very tired. After the trans swap and installing the LT1 starter I somehow managed to hook the wires up wrong and connected the battery. Had zero power in car. Went back and swapped the wiring back to the proper way. Car got power and ran but in limp. I'm assuming that's it as it wasn't in limp prior to the swap. I changed the ECM and used the original Memcal and still in limp. Only other thing I touched was snipping the wires off the auto shifter and set up reverse lights and clutch switch.

[EagleMark]

Maybe a fuse or still a wiring issue? Still don't think you hurt a memcal... ECM maybe...

[Z1LE]

Thanks... I'll start with the fuses. On OBD1 in limp with a solid engine light ... Does that indicate emissions failure? What sensors can trigger limp?

Kris

[RobertISaar]

sensor failure won't really trigger LHM.... i can't speak definitely for the TPI code, but i don't think even multiple sensor failure will trigger it.

in LHM, you'll probably fail emissions test standards 10-fold. it's that bad when you don't have the main processor doing the work.

[jimmykicker]

Yes I agree. I did do something that was a silly mistake being rushed and very tired. After the trans swap and installing the LT1 starter I somehow managed to hook the wires up wrong and connected the battery. Had zero power in car. Went back and swapped the wiring back to the proper way. Car got power and ran but in limp. I'm assuming that's it as it wasn't in limp prior to the swap. I changed the ECM and used the original Memcal and still in limp. Only other thing I touched was snipping the wires off the auto shifter and set up reverse lights and clutch switch.

Working on one tired is always a mistake. I stop now when I get tired because I start making dumb mistakes. I cooked my dash wiring in my 84 like that once by connecting a brown wire (taillights, inst cluster) to ground. Brown...not black... That cost me about a week of my time trying to source a wiring harness from a 26 year truck that wasn't in worse shape than mine.

Also when I did my swap to the TBI? I checked everything but the relay in the harness....guess what? It was full of broken pieces of stuff (I was unaware of it at the time.) Well there is a constant hot in there and wires that lead back to the ECM for fuel pump energizing....sounds bad? Yes. I plugged up the wiring harness to the ECM that was connected to a 20 amp (too high) fuse in an auxilary fuse box....the lights dimmed and it killed my ECM before I could snatch it loose. Made me really mad. I am guessing it grounded out to the negative post on the relay and killed it before the 20 amp blew. Live and learn I guess. Fortunately they are cheap and plentiful....

Never work tired. You will regret it.