ABS light on after MOT......now sorted......

[andy18n]

Hi all
Had first MOT since ownership on Z today. Flew through no problems but when I went to drive it away, ABS light came on and wouldn't go off. Stopped and started a couple of times, no change.
MOT man said drive a mile or so, pull over, stop and start again and it will go off, something to do with the brake test on MOT messing up the sensors.
Anyway unconvinced I did this and sure enough light went off and has stayed off since.
Sorry if this is a common or well known issue but may be useful for others if newbies like me!
Cheers
Andy

[Robert T]

I seem to recall this happening to someone else on here. Depending upon the brake test machine, it may cause the sensors to produce "implausible" values. They usually work by testing a pair of wheels at a time - which is not the normal way that a car is driven. ABS/ASC will normally reset itself after a couple of restarts. If it doesn't then you have a fault. Have to say that I don't particularly like the idea of taking my car in for an MOT and it coming back with warning lights showing, and this is not something that has every happened to me - couldn't tell you what brake testing machine my garage uses, but they are a BMW dealer who are in the process of going back to being independent.

Something else to watch for, if your car has an Limited Slip Differential, make sure that you inform the MOT tester of this, as some brake test machines are unsuitable for LSDs and/or they need to perform the test differently (I am sure someone on here can clarify this - neither of my cars have LSDs fitted).

Cheers R.

[motco]

I seem to recall this happening to someone else on here. Depending upon the brake test machine, it may cause the sensors to produce "implausible" values. They usually work by testing a pair of wheels at a time - which is not the normal way that a car is driven. ABS/ASC will normally reset itself after a couple of restarts. If it doesn't then you have a fault. Have to say that I don't particularly like the idea of taking my car in for an MOT and it coming back with warning lights showing, and this is not something that has every happened to me - couldn't tell you what brake testing machine my garage uses, but they are a BMW dealer who are in the process of going back to being independent.

Something else to watch for, if your car has an Limited Slip Differential, make sure that you inform the MOT tester of this, as some brake test machines are unsuitable for LSDs and/or they need to perform the test differently (I am sure someone on here can clarify this - neither of my cars have LSDs fitted).

Cheers R.

You're right about LSDs. I always tell my MOT tester that mine has an LSD, although it is a TORSEN type, and he uses the old Tapley meter technique. TORSEN LSDs are 'soft' in their action and probably don't need special treatment, but on the precautionary principle...

[pingu]

My car always seems to pass as the tester tells me he has to take it for a drive to test the brakes .