To make a short story long. I have an 81/95 (longer story) Jeep CJ7 with a SD TPI in it. I am running a turbo 350 trans. with vss from a 95 wrangler so my speedometer will work. The problem is that I finally hooked up my vss input to the ECM and the ecm is reading about 15 MPH faster than actual speed. I moved the road speed constant all the way down to 3614 PPM in TC and it is still 15 MPH off. Can I manually change the Bin to a lower PPM or am I at the minimum the ECM will recognize?

 

If the ecm is reading faster than actual you have to raise the PPM not lower them. My boss' truck had the same problem, it was reading double the actual MPH. I'm sure that it was at 4004 so try something higher than that. We put it to 8000 and it works perfect. However, I believe this is only good for what the ECM sees but I don't know that it will affect the speedometer output of the ecm. Or are you saying that your Jeep speedometer works off of the VSS and is not fed from the ecm?

 

I will try to raise the PPM tomorrow. I only lowered it to 3614 PPM today and though it was closer but I could be wrong. Yes, my VSS feeds the speedo directly so I tapped into the speedo feed wire for the ECM. Seems to work, just not accurately.