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ABS/TCS Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 18 Mar 2003 13:06:46
In Reply to: Help ABS and TCS lights came on yesterday, bill maidment, Mon, 17 Mar 2003 15:39:03 Members do not see ads below this line. - Help Keep This Site Online - Signup |
As was mentioned, the TCS uses the ABS sensors. So if the ABS thinks there is a problem with a sensor, the TCS will switch itself off also. This is different from TCS limp home. TCS limp home occurs when the TCS thinks there is a problem with the throttle part of TCS. It goes into Limp home to avoid a throttle run-away condition. If it's just an ABS sensor, TCS shuts itself off.
The ABS does two continuous tests. In the first test, it compares the resistance (impedance) of each ABS wheel sensor to the others. If one is out of range of the others, it turns on the ABS light. In the other test, it compares the speeds of all the wheels - if one wheel is going slower, AND the brakes aren't on, it figures there is a sensor problem.
There is a slight possibility a chain damaged a wheel sensor cable. Those cables are out in the path of danger from a loose chain. COuld be, but I doubt it.
When you put chains on, the effective diameter of that wheel gets bigger. So you travel farther for the same number of rotations. I'll assume the chains are only on the front wheels. So for the same 'speed' up front, the car is going faster. The rear wheels don't have chains, so they'll be turning faster.
I'll bet the ABS is seeing this difference and tripping a fault. It sees the rear wheels going faster than the fronts with the brakes off. That isn't a situation where the TCS would kick in, as if the fronts were slipping they would be going faster.
Why can some folks use chains OK? I'll bet some chains are slightly larger/thicker than others. Some sneak in under the fault threshold, others don't.
If you take the chains off and the problem goes away, I'll bet that's the issue.
Good luck!
posted by 192.249....
, Tue, 18 Mar 2003 13:06:46 <-- Viewing This Message
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