Speedometer/ABS Trouble
03-12-2007, 12:12 PM
#1
Race Car
Thread Starter
Speedometer/ABS Trouble
Hey guys, I know, it's been awhile. 
Recently, a friend of mine with a PRISTINE RS America has developed an issue with it. He had a battery go dead in it so he replaced it and noticed that the ABS/Airbag lights were on and the speedometer isn't working.
We had his car hooked up to the laptop version of the Porsche Diagnostic Tool and was able to extinguish the airbag light but his ABS light is still on and the speedometer still doesn't work.
The local tech. who was helping us suggested we swap out the speedometer, according to the indications on his diagnostic tool as it is connected to the ABS speed sensors, etc. I understand swapping out the speedometer because it's not working, but is it possible it will fix the ABS problem as well??
He stated that we did NOT have a bad speed sensor, we took the ABS computer out of my car and installed it in his RSA, hooked up the diagnostic tool and NO fix.
BTW, neglected to mention that my friends ABS is NOT working, found this out by surprise about a week ago when we were futzing around on a backroad and he locked 'em up - SCARY!!
A couple questions:
1 - has anyone else had this issue, if so, was it speedometer related?
2 - does anyone have info. regarding how the speedometer is connected to the ABS and the possibility of a bad speedometer (or ckt. board) affects the ABS??
3 - last question, for now - does anyone have a spare speedometer they can loan us for troubleshooting? I guarantee it will be returned in the condition it was sent (maybe with less dust on it...haha) and ALL testing/swapout will be conducted by a local Master Porsche Technician.
Thanks to Colin-Chin-Alloy for loaning me an AFM a few months ago, turns out that was EXACTLY what was ailing my 964, procured a good used unit from eBay and the car showed a 32HP improvement on the dyno last month - CRIKEY!!
Recently, a friend of mine with a PRISTINE RS America has developed an issue with it. He had a battery go dead in it so he replaced it and noticed that the ABS/Airbag lights were on and the speedometer isn't working.
We had his car hooked up to the laptop version of the Porsche Diagnostic Tool and was able to extinguish the airbag light but his ABS light is still on and the speedometer still doesn't work.
The local tech. who was helping us suggested we swap out the speedometer, according to the indications on his diagnostic tool as it is connected to the ABS speed sensors, etc. I understand swapping out the speedometer because it's not working, but is it possible it will fix the ABS problem as well??
He stated that we did NOT have a bad speed sensor, we took the ABS computer out of my car and installed it in his RSA, hooked up the diagnostic tool and NO fix.
BTW, neglected to mention that my friends ABS is NOT working, found this out by surprise about a week ago when we were futzing around on a backroad and he locked 'em up - SCARY!!
A couple questions:
1 - has anyone else had this issue, if so, was it speedometer related?
2 - does anyone have info. regarding how the speedometer is connected to the ABS and the possibility of a bad speedometer (or ckt. board) affects the ABS??
3 - last question, for now - does anyone have a spare speedometer they can loan us for troubleshooting? I guarantee it will be returned in the condition it was sent (maybe with less dust on it...haha) and ALL testing/swapout will be conducted by a local Master Porsche Technician.
Thanks to Colin-Chin-Alloy for loaning me an AFM a few months ago, turns out that was EXACTLY what was ailing my 964, procured a good used unit from eBay and the car showed a 32HP improvement on the dyno last month - CRIKEY!!
03-12-2007, 12:42 PM
#2
Race Car
Thread Starter
Addendum: I realize that ground points and speed sensors can be swapped out, etc. - I have NO problem taking the "donors" from my car when we get a chance to take the wheels off both cars and are able to swap this around, but getting to my speedo is VERY difficult due to the rollcage, etc. and figure troubleshooting could be a bit easier with a handy spare.
I have read the posts from the search function and we have checked most of the items on the list but not much on grounding points with exception to the ABS unit. I will verify the pins on his plug in harness, etc. and go from there.
In short, if anyone has any other advice and/or a spare speedo we can work with, please let me know via PM - thanks!
I have read the posts from the search function and we have checked most of the items on the list but not much on grounding points with exception to the ABS unit. I will verify the pins on his plug in harness, etc. and go from there.
In short, if anyone has any other advice and/or a spare speedo we can work with, please let me know via PM - thanks!
03-12-2007, 01:28 PM
#3
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jeff - the ABS relay is the most likely issue. the Speedo depends on the ABS wheel speed pulse from the ABS brain - this is routed through the relay and to the speedo.
you should try swaping the relay first with a known good one, before doing anything else. the Relays do go bad and if there was an overvoltage it could have fried.
btw - i have the ABS wiring diagram up on our site sicne you need to jumper and run the ABS relay power to the dash switch.
When you kill ABS you kill the Speedo and Odo as well
http://www.carreracupusa.org/Race/el...electrical.htm
you should try swaping the relay first with a known good one, before doing anything else. the Relays do go bad and if there was an overvoltage it could have fried.
btw - i have the ABS wiring diagram up on our site sicne you need to jumper and run the ABS relay power to the dash switch.
When you kill ABS you kill the Speedo and Odo as well
http://www.carreracupusa.org/Race/el...electrical.htm
03-12-2007, 01:31 PM
#4
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Rennlist Member
Rennlist Member
You have check the fuses (replaced) and checked for any loose connections at the fuse box? Pulling the fuse results in the symptoms you describe. As Rob suggests, I'd check the relay too - I had a power drain that took forever to figure out that was due to a bad relay.
