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Re: Another VSS question
[Re: Dabee]
#2060694
04/24/16 10:26 AM
04/24/16 10:26 AM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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Mismatch refers to tire diameter. PCM expects to see a certain engine rpm at a certain road speed, within a certain tolerance.
You need to match the tire diameter to the PCM donor or get the computer reprogrammed to account for the new tire size. Assuming a 97 1/2ton van it's a 29" tire, P235/75R15. What are you running?
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Another VSS question
[Re: Supercuda]
#2060712
04/24/16 10:58 AM
04/24/16 10:58 AM
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Joined: Nov 2003
Posts: 3,461 Dandridge TN
Dabee
OP
master
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OP
master
Joined: Nov 2003
Posts: 3,461
Dandridge TN
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Mismatch refers to tire diameter. PCM expects to see a certain engine rpm at a certain road speed, within a certain tolerance.
You need to match the tire diameter to the PCM donor or get the computer reprogrammed to account for the new tire size. Assuming a 97 1/2ton van it's a 29" tire, P235/75R15. What are you running? Thanks, that's what I thought. Since the PCM is a reman, I don't know what vehicle it came out of. I have 245/70/17 tires on the rear. 30.5 inch dia. The VSS is in the trans tail shaft, no ABS on the truck, so all the PCM is seeing is the trans out put speed vers engine speed. Changing tire size or gear ratio doesn't change that relationship.
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Re: Another VSS question
[Re: moparx]
#2060923
04/24/16 06:26 PM
04/24/16 06:26 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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The tire programming on all the Mopars I remember when I worked at the dealer in the 90's up to 2010 was all done in the Anti-Lock Brake module. I forgot what year but they started using the ABS sensor in the rear diff for the speedo also and we had to program tire size in the ABS module. They had a selection of sizes and if the size you had was not in there you could also program it in by "Revolutions per Mile". I dont remember the PCM's having any option to program tire size but we did program some Trans modules on front wheel drive with what was called "Pinion Factor". But again that was in the TCM (trans Control Module). I have been out of its since 2011 but I dont remember any options in the PCM's for programing tire size as it was done in the ABS or trans module and then that info was bussed to the PCM. Ron
Last edited by 383man; 04/24/16 06:30 PM.
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