I converted my 165 ecm to the 7749 last year and have noticed the speedometer at cruising speeds is about 5mph high. I have confirmed this with two different vehicles. I set the road speed constant according to this link:

http://www.speedtoys.com/~bort62/7749/Main.htm

It is originally a MAF car, and if I remember correctly, I set it at 4006 in programmer.

My question is how can I correct the 5 mph error, do I move the number above up or down, and how much?
thanks again for your help,
Mark

 

i think you need to set it higher, try 4024 & see what you have, if it goes the wrong way, then try 3988. i don't remember just how much of a change it will make, its the trail & error method.

 

The speedometer in the dash is connected to the VSS buffer. The buffer connected to the tranny sender, and also to the ECM. changing the constant in the ECM will correct the log, but not your speedometer gauge in the dash.

I've been trying to figure this one out as well. I *think* you can wire the speedometer in the dash directly to the VSS out pin on the '730/'749 (used for cruise control) but i'd check with Bruce first. he's a lot better at the code than I am.

-- Joe

 

Guys,
thanks for the info. I will reply to this to see if we can get anymore hits from the experts.
Mark

 

I'm doing a vaguely similar swap right now and I'm running pin 11 (brn) of my DRAC (VSS buffer) to pin C6 of my 7730.