Just did a Dakota Digital VHX gauge swap on my Chevelle. I though I could just piggy back the VSS signal wire to the trans near the sensor. It's working on the gauge but now the car is throwing a "VSS signal low voltage" and the transmission will not properly shift itself.

I immediately turned around and parked it.

Is there anything I could do to fix it as is or is there a better way it needs to be hooked up? Is there a pin out on the pcm or does it function stock gauges through a separate body harness or something?

 

Yes, the PCM has a Speedometer out signal.
Tell me what year your PCM is and I and someone else will have the doco for it.

 

Yes, the PCM has a Speedometer out signal.
Tell me what year your PCM is and I or someone else will have the doco for it.

 

It is a 99 pcm and harness for a fbody.

Thanks

 

EDIT: on my car the correct pin was Red 55, green with white stripe wire

I've been searching and it seems like the best answer I can get is I did it wrong and it's causing the problem and the solution is to get my needed signal from the PCM on the Red C2 plug in pin #50 which is a green/white VSS out

 

That is right. I fed it into my Autometer digital speedometer and it worked perfectly.

BTW - If convenient, I would suggest switching to a 2002 PCM which is pinout compatible. I don't remember all the advantages that have been mentioned in the tuning section on this forum, but it is generally preferred.
For me one advantage is that the 2002 lets you log twice as many parameters simultaneously as earlier ones. If you plan to do a lot of tuning yourself, that is a big advantage.

 

I pulled the pcm and mine did not have a wire in the 50 slot but it did have a green/white in the 55 slot.

Tapped into that one and it works like a charm. Just wanted to post here in case this turns up in a search.

 

Finding the VSS signal on pin 55 of the Red C2 plug indicates you have a '98 PCM, not a '99. The '98 has a completely different pinout than the other years. The F-body '99-'02 and Corvette '97-'05 all have about the same pinout, as do most of the truck during those years.

I first had a '98 PCM, but changed last fall to a '02 which required moving all the pins. I bought an extra set of connectors so that I could move the wires one by one.

 

Could it be an early 99 issue? It required EFI live credits to tune it (97-98 do not) and I have tuned 98s for 2 friends and the tables are a good bit different in them.

Unless when I sent to pcm off to be tuned by wait4me originally the newer operating system could be loaded into it? I did not think that was possible. I am almost certain it lists itself in EFI live as 99 Firebird. I have also fired the car on another supposed 99+ style pcm before, but did not drive it.