Kill the ABS warning
07-08-2007, 04:06 AM
#16
I went through a similar process of elimination in trying to get my RDK system working and discovered that first-principle logic such as this doesn't always help when dealing with electronics.
If you are sure the fuse and relays are OK you probably have a defective ABS 'brain'. Porsche dealers and others with Bosch diagnostic equipment can identify your fault or alternately you could test it yourself by swapping it with a known good one. Unfortunately many later cars had the PSD brain integral with the ABS one so they won't fit. An ABS brain for your 89 might be hard to find. Any '90 or earlier ABS-equipped cars in the Edmonton area?
I bought a used one from 928 Intl for $100 in '03 and it's still working.
Luck with it.
Colin. 89GT
If you are sure the fuse and relays are OK you probably have a defective ABS 'brain'. Porsche dealers and others with Bosch diagnostic equipment can identify your fault or alternately you could test it yourself by swapping it with a known good one. Unfortunately many later cars had the PSD brain integral with the ABS one so they won't fit. An ABS brain for your 89 might be hard to find. Any '90 or earlier ABS-equipped cars in the Edmonton area?
I bought a used one from 928 Intl for $100 in '03 and it's still working.
Luck with it.
Colin. 89GT
07-08-2007, 06:00 AM
#17
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Brain, your initial logic (unplug all 4 then pulg one in at a time until you find the one that doesn't cause a fault, cos it doesn't work) makes sense to me, admittedly I am not an automotive or otherwise electronics expert.
I'ld start by looking at the left rear wheel circuit more closely.
However
IIRC you have to get to have enough speed over the ground to get enough volts through the circuits to make any of it work at all (or not) Is it possible that your test pushing the car could have got enough speed on one sensor but not on the others.
I'ld start by looking at the left rear wheel circuit more closely.
However
IIRC you have to get to have enough speed over the ground to get enough volts through the circuits to make any of it work at all (or not) Is it possible that your test pushing the car could have got enough speed on one sensor but not on the others.
07-08-2007, 12:04 PM
#18
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Actually, I drove the car down the alley for the individual sensor test after I discovered that I could not spin the wheel fast enough on the jack. Admittedly, for some sensors, it seemed to take different "roll distances" to set the error message. Might this be an issue?
The left rear sensor was replaced and then threw a signal (error message) just like all the rest......
The left rear sensor was replaced and then threw a signal (error message) just like all the rest......
07-08-2007, 12:06 PM
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Originally Posted by ColinB
I went through a similar process of elimination in trying to get my RDK system working and discovered that first-principle logic such as this doesn't always help when dealing with electronics.
If you are sure the fuse and relays are OK you probably have a defective ABS 'brain'. Porsche dealers and others with Bosch diagnostic equipment can identify your fault or alternately you could test it yourself by swapping it with a known good one. Unfortunately many later cars had the PSD brain integral with the ABS one so they won't fit. An ABS brain for your 89 might be hard to find. Any '90 or earlier ABS-equipped cars in the Edmonton area?
I bought a used one from 928 Intl for $100 in '03 and it's still working.
Luck with it.
Colin. 89GT
If you are sure the fuse and relays are OK you probably have a defective ABS 'brain'. Porsche dealers and others with Bosch diagnostic equipment can identify your fault or alternately you could test it yourself by swapping it with a known good one. Unfortunately many later cars had the PSD brain integral with the ABS one so they won't fit. An ABS brain for your 89 might be hard to find. Any '90 or earlier ABS-equipped cars in the Edmonton area?
I bought a used one from 928 Intl for $100 in '03 and it's still working.
Luck with it.
Colin. 89GT
Where is the brain??
07-09-2007, 07:13 AM
#20
Brian.
Lucky you indeed. The brain is a flat aluminium box about the size of a paperback book IIRC, located under the dash. According to the wiring diagrams yours should be mounted vertically on the left side above the drivers footwell somewhere but I'm not sure about that. My car's RHD. Any LHD owners help here? Caution. There are other similar-looking brains under there. Make sure the part numbers on both cars are the same.
Colin. 89GT
Lucky you indeed. The brain is a flat aluminium box about the size of a paperback book IIRC, located under the dash. According to the wiring diagrams yours should be mounted vertically on the left side above the drivers footwell somewhere but I'm not sure about that. My car's RHD. Any LHD owners help here? Caution. There are other similar-looking brains under there. Make sure the part numbers on both cars are the same.
Colin. 89GT
07-09-2007, 06:48 PM
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07-09-2007, 07:18 PM
#22
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Brian - what wheels/tires are you running - how far off stock are they? and if different from stock how different is the % difference to stock between fronts & rears...
Alan
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07-10-2007, 03:31 PM
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Originally Posted by Alan
Brian - what wheels/tires are you running - how far off stock are they? and if different from stock how different is the % difference to stock between fronts & rears...
Alan
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07-11-2007, 09:36 PM
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A recent post in another thread reminded me of something here......
On start-up there is no "test-cycle" buzz in the brake pedal upon first depression, as there is on the '87 car with working ABS.....
Does this tell us something???
On start-up there is no "test-cycle" buzz in the brake pedal upon first depression, as there is on the '87 car with working ABS.....
Does this tell us something???
08-15-2007, 11:10 PM
#25
Race Car
Originally Posted by RichS 1986928
Not sure if it will help you with the 89 but on my 86, if you disconnect the wiring harness to
the pump inside the driver's front fender, the ABS light goes off for good.
the pump inside the driver's front fender, the ABS light goes off for good.
Accessed from within the wheel well?
Thanks!
08-15-2007, 11:35 PM
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I honestly don't know for sure but I don't see why this would make the brakes
work any differently than when the system is disabled by other means, like fuse, relay or
error message.
Yes, accessed from inside the driver wheel well, must remove the plastic shield.
I'm still trying to get to actually fixing my ABS completely.. still living with the light!
work any differently than when the system is disabled by other means, like fuse, relay or
error message.
Yes, accessed from inside the driver wheel well, must remove the plastic shield.
I'm still trying to get to actually fixing my ABS completely.. still living with the light!
08-17-2007, 02:41 AM
#28
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If you pull all of the ABS sensors from their plug sockets at the wheel the ABS gets no info so doesn't see anything amiss.... so no error message is generated.... no lights not nothing. There is even a blank plug hole in the socket, along with the pad-wear sensor plug.
08-18-2007, 07:16 AM
#29
Brian
I'm at home now and checked for that "test-cycle buzz" you spoke of in the brake pedal. Doesn't happen on my car and I've never heard anybody else mention it. BTW the extra blank holes in the "junction boxes" (sockets as you refer) are for the connectors for those cars fitted with the RDK tyre-pressure sensor system.
Colin. 89GT
I'm at home now and checked for that "test-cycle buzz" you spoke of in the brake pedal. Doesn't happen on my car and I've never heard anybody else mention it. BTW the extra blank holes in the "junction boxes" (sockets as you refer) are for the connectors for those cars fitted with the RDK tyre-pressure sensor system.
Colin. 89GT
08-18-2007, 10:21 AM
#30
Race Car
How is this for weird. I get the ABS warning light upon startup. Hit the ! button to cancel the big red warning light and the ABS light stays on as expected. Now for the wierd part. I have seen two intermittent things happen while driving:
1) the ABS light goes out, implying that the ABS system is back on. Then a bit later, I get the ! again and the warning light.
2) A couple of times I noticed the ! light come on again, but don't think the ABS light ever went out. A cancelled warning comes back.
I am going to try disconnecting the ABS harness in the fender wheel well this evening, but as far as fixing the problem long term, this intermittent stuff sounds challenging to trace.
Any thoughts?
Thanks!
1) the ABS light goes out, implying that the ABS system is back on. Then a bit later, I get the ! again and the warning light.
2) A couple of times I noticed the ! light come on again, but don't think the ABS light ever went out. A cancelled warning comes back.
I am going to try disconnecting the ABS harness in the fender wheel well this evening, but as far as fixing the problem long term, this intermittent stuff sounds challenging to trace.
Any thoughts?
Thanks!