You can't assume PCM controls the Speedo. You or someone else must follow wiring setup.
Even then PCM needs scanning to see is it to have same error.
Just having different tires vs doner vehicle can cause 5 mph.
[QUOTE]Originally posted by sleek fiero: Am I crazy but weren't there several optional drive gears for the VSS that were optional depending on final drive ratio ?
Yes. Even if you "read" speed on the axle itself... Total Tire Diameter can change actual road speed. So a gear change is needed for "dumb" speedos whether cable type or VSS system w/ direct to speedo or older ECMs.
Many to all OBD2 PCM have some kind of Tire Size data because hard to change the speedo gears on most old cars and so most never even tried. Even w/ OBD2, you often need High $ scanner and often a High $ monthly/yearly subscription to access this function or pay Dealer Price for them to change tire size. W/ engine swaps, most Dealers won't help you.[/QUOTE]
Friend of mine says we can get hptuners set up on my laptop and calibrate the setting in the pcm that way?
sdgdf
JAN 16, 05:38 PM
quote
Originally posted by J Gunsett:
First you have a PM. You stated 5mph off at 60, how far off is it at 20. Is the needle steady or jumping around as you drive?
I might be able to check mph when I get home later, the needle is steady. It just acts like it’s tuned for the donor car.
sanderson231
JAN 16, 09:54 PM
quote
Originally posted by sdgdf:
It’s from a 2000 Grand Prix GTP.
2000 is OBD-II. The chip is flashable. The HP tuners VCM editor software should allow the vehicle speed constant to be changed.
------------------ formerly known as sanderson 1984 Quad 4 1886 SE 2.8L 1988 4.9L Cadillac 1988 3800 Supercharged
