VSS/TOS problems. Early TCC. 8625 [7427/$0d]
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VSS/TOS problems. Early TCC. 8625 [7427/$0d]
I recently started having an early TCC lockup issue out of the blue (4l80e). I've traced the hack, and now I'm dumbfounded as to what's actually wrong.
My TOSMPH [L00CD]] is 80 ("40mph") when I'm only doing 15mph. When I hit 3rd gear, PCM thinks I'm fast enough to lock the TCC based on TOSMPH. The compare is LC6b7 CMPA L00D1 in $0d.. Upshifts occur at proper speed (looking into that ATM, code must not be using the TOSMPH for shift points...)
My TOS RPM(X8) [L0126] is way high by my rough calculations (should be ~35-45% of what the PCM is recording). I have no data logs with these memory bytes from before this started, so I'm not 100% sure if the TOSRPM pulse counter is artificially high or not.
The 2000ppm input records the correct speed, which matches my speedo. No change if I bypass the DRAC and input the speed directly on f4/f5 (flag 5D02, TOS not from drac).
Also no change with another VSS, or my spare PCM, and/or a fresh bin.. It's possible both my PCMs now have an issue reading TOS, but wtf??
My TOSMPH [L00CD]] is 80 ("40mph") when I'm only doing 15mph. When I hit 3rd gear, PCM thinks I'm fast enough to lock the TCC based on TOSMPH. The compare is LC6b7 CMPA L00D1 in $0d.. Upshifts occur at proper speed (looking into that ATM, code must not be using the TOSMPH for shift points...)
My TOS RPM(X8) [L0126] is way high by my rough calculations (should be ~35-45% of what the PCM is recording). I have no data logs with these memory bytes from before this started, so I'm not 100% sure if the TOSRPM pulse counter is artificially high or not.
The 2000ppm input records the correct speed, which matches my speedo. No change if I bypass the DRAC and input the speed directly on f4/f5 (flag 5D02, TOS not from drac).
Also no change with another VSS, or my spare PCM, and/or a fresh bin.. It's possible both my PCMs now have an issue reading TOS, but wtf??
Last edited by helo; Jul 7, 2011 at 02:59 PM.
Thread Starter
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Joined: Dec 2010
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Re: VSS/TOS problems. Early TCC. 8625 [7427/$0d]
I take it nobody has seen anything like this before..
*shrug* For now, I hacked my bin to just copy MPH from 02a7 (or somewhere?), multiply by 2 and save as 00d1 (TOSMPH).
My shift points were also low, I just didn't realize it until I looked at my logs more closely.
Hopefully I can sort out what's actually wrong during my next days off. The 2000ppm VSS seems to have very slow resolution when coming to a quick stop. I calculated 40ppr as something like 108000ppm with my gearing/tires.
*shrug* For now, I hacked my bin to just copy MPH from 02a7 (or somewhere?), multiply by 2 and save as 00d1 (TOSMPH).
My shift points were also low, I just didn't realize it until I looked at my logs more closely.
Hopefully I can sort out what's actually wrong during my next days off. The 2000ppm VSS seems to have very slow resolution when coming to a quick stop. I calculated 40ppr as something like 108000ppm with my gearing/tires.
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