intermittent ABS / Rear Diff warning
02-22-2010, 03:18 PM
#1
Addict
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intermittent ABS / Rear Diff warning
I am getting an occasional ABS / rear diff warning when driving on the highway.
Sometimes it doesn't come on for days, sometimes it comes on twice a day. Always on the highway 50 MPH or higher. Then the ABS stays disabled until a restart...
'91 S4
Any suggestions where to start looking?
thanks
Sometimes it doesn't come on for days, sometimes it comes on twice a day. Always on the highway 50 MPH or higher. Then the ABS stays disabled until a restart...
'91 S4
Any suggestions where to start looking?
thanks
02-22-2010, 03:31 PM
#2
Three Wheelin'
My similar experience...
I had the same problem for a while in my case it was resloved by running the PSD slave through the pressure build-up release cycle with the hammer.
Under most regular driving conditions the PSD doesn't get activated that often and over time the slave cylinder gets stuck.
Good luck
Under most regular driving conditions the PSD doesn't get activated that often and over time the slave cylinder gets stuck.
Good luck
02-22-2010, 03:43 PM
#3
Supercharged
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A PSD flush and fill might be a good thing to do if it hasn't been done for a while.
Could also be a failure at one of the wheel speed sensors. I've read where little metal filings can build up on the speed sensors (actually, the rotating part, not the pickup) at the wheels. If it the PSD/ABS brain senses a failure or wrong signal it shuts down the whole system (all the same brain).
Could also be a failure at one of the wheel speed sensors. I've read where little metal filings can build up on the speed sensors (actually, the rotating part, not the pickup) at the wheels. If it the PSD/ABS brain senses a failure or wrong signal it shuts down the whole system (all the same brain).
02-22-2010, 03:53 PM
#4
There are 14 diagnostic fault codes that can be registered with the PSD/ABS.
The codes and troubleshooting guide is shown in the WSM, Vol. 3 pages D39-201 to D39-260 and in Vol 4 pages 45-08 to 45-10.
As Herman suggested you will need to have your system checked with one of the diagnostic tool to identify the fault and activate the slave cylinder.
I would suggest that the PSD unit has it brake fluid changed and the system activated via this procedure.
In addition I would check the ABS speed sensors on each wheel to ensure that the sensors are clean, the connectors are making good contact and also that the motion rings are clean.
Tails 1990 928S4 Auto
The codes and troubleshooting guide is shown in the WSM, Vol. 3 pages D39-201 to D39-260 and in Vol 4 pages 45-08 to 45-10.
As Herman suggested you will need to have your system checked with one of the diagnostic tool to identify the fault and activate the slave cylinder.
I would suggest that the PSD unit has it brake fluid changed and the system activated via this procedure.
In addition I would check the ABS speed sensors on each wheel to ensure that the sensors are clean, the connectors are making good contact and also that the motion rings are clean.
Tails 1990 928S4 Auto