Help diagnose low speed ABS activation on dry pavement, < 5mph all stops
01-16-2006, 09:21 AM
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Help diagnose low speed ABS activation on dry pavement, < 5mph all stops
ABS kicks in upon normal braking (< 5mph) regularly, example when slowing for a stop sign. Searched on AW and found out that the wheel speed sensors can get dirty and cause this problem.
I pulled the fronts sensors out and cleaned them both. Did not help the problem.
Today I tried to do the rears, but broke off the mounting bolt on the 1st one so I did not attempt to pull the sensor (I'm not ready to drill out the broken bolt & retap this just yet) so I just left it.
Figured I'd fire up Vag-com (ISO-COM/311-2) so see if there was a problem with the ABS controller, and try to use measuring blocks to see if there was weak/dead sensor.
I can log into the ABS module, shows no fault codes. If I click on Measuring Blocks, block 001 shows "Speed" "Speed" "Speed" "Speed". I assumed these were the 4 wheel sensors. So I start driving and see the KM/HR go up on all 4 of the indicators. So I would assume my 4 wheel sensors are fine, reading equal to each other.
After 1 min, I get "can't communicate with controller, Retry?" and measuring stops. If I click to retry, it fails repeatedly.
I can't seem to hold connection to the ABS module. I think it also did this with the key in the "on" position before I did the test drive. (I posted this Q over in the VAG-com forum to see about his issue...)
But, where else can I look to solve this ABS problem?
Should I try pulling the ABS fuse to see what happens?
Help... wife is getting very irratated at this ABS issue.
Vic
I pulled the fronts sensors out and cleaned them both. Did not help the problem.
Today I tried to do the rears, but broke off the mounting bolt on the 1st one so I did not attempt to pull the sensor (I'm not ready to drill out the broken bolt & retap this just yet) so I just left it.
Figured I'd fire up Vag-com (ISO-COM/311-2) so see if there was a problem with the ABS controller, and try to use measuring blocks to see if there was weak/dead sensor.
I can log into the ABS module, shows no fault codes. If I click on Measuring Blocks, block 001 shows "Speed" "Speed" "Speed" "Speed". I assumed these were the 4 wheel sensors. So I start driving and see the KM/HR go up on all 4 of the indicators. So I would assume my 4 wheel sensors are fine, reading equal to each other.
After 1 min, I get "can't communicate with controller, Retry?" and measuring stops. If I click to retry, it fails repeatedly.
I can't seem to hold connection to the ABS module. I think it also did this with the key in the "on" position before I did the test drive. (I posted this Q over in the VAG-com forum to see about his issue...)
But, where else can I look to solve this ABS problem?
Should I try pulling the ABS fuse to see what happens?
Help... wife is getting very irratated at this ABS issue.
Vic
01-16-2006, 10:08 AM
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Clean off all the sensors....
Audis have a way of getting a tremendous build-up of brake dust on the sensors. I used to get a bit of that, not much, only if the car was agressively driven. Having replaced all 4 wheel bearings and cleaned the sensors completely, the abs does not trip anymore. It also helped by installing ATE Power Discs(slotted rotors), they eliminated the brake fade.
01-16-2006, 10:21 AM
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are the rears as tight a fit as the fronts? Wonder why they tacked down the backs
and not the fronts.
As you can assume, I'm nervous about pulling that back one out and it being loose till I can drill the broken piece out.
WIth it being 15 deg. out makes for working on the vehicle the suck...
As you can assume, I'm nervous about pulling that back one out and it being loose till I can drill the broken piece out.
WIth it being 15 deg. out makes for working on the vehicle the suck...
01-16-2006, 11:13 AM
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Usually tightness is not the issue, its corrosion......
They are a snug fit, but once cleaned and lubricated, they are easy to fit/remove again. If you live in an area where they use "road salt" or chemicals, the stuff just sits in there after a drive and corrodes the ring and hub around it. They bolt them down so if they ride out, the sensor does not get caught in the wheel or brake assembly.
01-16-2006, 11:35 AM
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A comment...
Hit the bolts with some Liquid wrench or the like and let it sit on there for a few hours before you attempt removing the bolt. Also, put an allen socket into the bolt and tap the end with a hammer, not too hard. This will loosen the threads up and usually break some of the rust up as well. You can also use an impact driver in reverse which will break the bolt loose but thats overkill.
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01-16-2006, 12:01 PM
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Ours still look like new, but just driven as a daily commuter....
If we were driving it more agressively(track, autoX, etc), I would consider a different pad compound and brake ducting. The slotted rotor has made a huge difference for us in oem pad life as well. Clearly the brakes are not getting as hot as they used to. After replacing the bearings the other day , the front pads still looked like day one.