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A few ideas Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 7 Apr 2006 06:46:26
In Reply to: ABS Light problem has me stumped, LIFETIMEOFSAABS  [Profile/Gallery]
, Thu, 6 Apr 2006 11:46:52
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First-
You say the brake fluid reservoir is at the FULL mark. If the car has sat overnight, what is the fluid level? It should be ABOVE the full line. When you start the car, you should hear the ABS pump run, and the level should drop to the FULL line. You need to let the car sit for a while (overnight is good) to let the system leak down the ABS pressure. If the level isn't moving, that's a bad sign. However, I would expect that you wouldn't have any brake boost, and would notice that.
Next - how long has this been going on? Something new in a car where it used to be fine, or it's been this way since you got the car?
Another question - does the ABS work? Have you been able to lock up the wheels on slippery surfaces, or do you feel the ABS kick in?
My initial suspicion is that you have two, possibly three problems. That's why understanding the history is important. It's unlikely they'd all happen at once, but if the car came this way, they could have failed one at a time.
My thoughts -
Assuming the ABS doesn't work, you've got an ABS fault. This could be as bad as the ECU being bad. At a minimum, unplug the ABS box and see if the wire from the ECU to the light isn't shorted out. Also, the ABS relay may be bad, or it could be as simple as the connector on the ABS box is making poor connection. The ABS box can turn the light on, but if the ABS relay isn't powered, the ABS light will be on. The ABS relay has a fuse next to it, and requires a ground signal from the ABS ECU to pull in.
The other light problems - parking brake and brake fluid lights - could be a few issues. Inside the instrument cluster both of those lights are connected by diodes to a device in the cluster. I'm using my Mitchell schematics right now, and they give very little detail; I'd want to check my Bentley manual for more information. If that device, which I suspect is some sort of power -on test thingy, were to go bad, it could turn on both lights at the same time. I'd have to do more research to see what it was.
Alternatively, if one of those diodes were to fail shorted (which they can do), then turning on the bulb associated with the shorted bulb would turn on the other. Possibilities are a problem with the parking brake switch, or a switch on the back of the master cylinder. This switch comes on if you push the pedal too far. This is really just a light to tell you the pedal has gone to the floor. But if the switch is bad, that could be the issue.
At a minimum, I think you have at least two different problems.
posted by 192.249....
, Thu, 6 Apr 2006 11:46:52, Fri, 7 Apr 2006 06:46:26 <-- Viewing This Message, Fri, 7 Apr 2006 11:31:02, Thu, 6 Apr 2006 18:52:37
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