Any ideas as to why my PCM and TCM are showing different speeds in the log? My speedo also bounces from 0 to 250mph as soon as the car starts moving.
Any ideas as to why my PCM and TCM are showing different speeds in the log? My speedo also bounces from 0 to 250mph as soon as the car starts moving.
Last edited by smallblock500; 06-22-2023 at 06:06 PM.
2001 V6 M5 firebird: drop in K&N, 12bolt with posi and 4.30s, magnaflow muffler, gutted cat.
9.5 at 73 in the 1/8th on street tires
Probably would be a good idea to mention up front that it's a swap vehicle with an aftermarket speedo/cluster.
The gauge is something different the problem I'm asking about is all internal to the pcm/tcm. This is what I'm trying to fix now. The faster you go the further off it is.
2001 V6 M5 firebird: drop in K&N, 12bolt with posi and 4.30s, magnaflow muffler, gutted cat.
9.5 at 73 in the 1/8th on street tires
Try running the speedo calibration tab again even if you have the same tire/gear to put in.
The ECM has a speedo calibration and the TCM has a speedo cal. Since you are swapping TCM's around I'm sure the two are setup for different gear/tire setups.
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What do you mean running the speedo calibration tab?
EDIT tab> Gear and Tire Wizard
Ok I did that and also doing another write entire on the pcm and tcm incase it missed something. It missed the vin one time it jar came out as all "eeEEEeeeeeEe"
redoing the gear calc made them closer but still not the same. Before 10mph was 24 now 10 mph is 13
2001 V6 M5 firebird: drop in K&N, 12bolt with posi and 4.30s, magnaflow muffler, gutted cat.
9.5 at 73 in the 1/8th on street tires
My bad. Forgot to add. When you do the tire/gear wizard you need the ACTUAL MEASURED tire diameter. NOT whatever is advertised or written on the side of the tire. Larger off road tires can be as much as 2.5 inches shorter than what it is advertised/listed as.
If it is correct than adjust the tire by one inch up or down and drive. You will get down to the .2 or so and be dead nutz
Its in a C3 corvette so no offroad tires here. The main thing I'm chasing is why the pcm and tcm are not showing the same speed. I'm not worried about pcm speed vs actual gps speed that part is easy. If the TCM reads the speed from the trans then sends that signal to the pcm why are they not the same?
2001 V6 M5 firebird: drop in K&N, 12bolt with posi and 4.30s, magnaflow muffler, gutted cat.
9.5 at 73 in the 1/8th on street tires
You have not attached a tune file so having a wild ass guess that it likely to be wrong you have a different differential gear than what is actually in the vehicle.
That would make the pcm and tcm show different speeds than each other even though they are reading the same speed sensor? I would think adjusting the gear ratios and tire size would make at least one of them match up to the gps on my phone right?
Also the 4.10 gear ratio and 25.67" tire data has been put in.
I'm posting from my phone but I'll post the tune file tomorrow.
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