They probably did check it ..the problem is you have to check it right after the fault appears..if it does not do it for a few cycles after that, then it clears itself. That is the problem with imtermittant faults ..and the most common one on ASR is the Brake lamp switch..your in traffic condition is were the brake is used the most and many guys that can not find an offending ASR code change the brake switch and the problem clears up..
You can go into that pin yourself with a simple Led/sw tool to check it, if you are handy...that is what I would do next.......
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