ABS

[RizzoTheRat]

Met some sheet ice going down a hill last night and the car actually started accelerating down the hill in a slide. When I got some grip again the engine braking slowed the car quite rapidly and the ABS light came on. When I got back on to treated roads I turned the engine off and back on again and the light went out. Is there likely to be some sensor on my 306 that worked out it was icy and turned it off?

[paintman]

Or if all wheels were locked did the ABS actually think you were stationary?

[RizzoTheRat]

They weren't locked, I was in first with the engine on tickover to roll gently down the hill, the sudden slowdown when I got some grip was due to the engine braking, I didn't touch the brakes at all.

[JonathanKK]

There was probably some form of implausibility with wheel speeds and brake pressures. If this happens ABS thinks something is wrong and shuts down. As long as the light is extinguished after ignition check, all is well again.

[100SRV]

As previous poster said it is likely that the ABS became confused - from an inputs point of view it compares wheel speeds, looks for brake applied, reads engine speed off databus also. Discrepancy between perceived road speed and engine speed (undriven wheels turning faster than driven) with no brakes applied lead it to believe there is an ABS failure - worth checking for fault codes.

I have rectified problems on a brand new truck which would get into 2nd gear (Allison 3000 series Automatic) then drop back into first gear and torque limit - the fault was that the first steer axle wheel speed sensors weren't "seeing" the tone rings but the rear ones were - ABS thought that there was rear wheel spin but as it was common mode (i.e. both wheels) it reduced engine torque rather than using ASR (acceleration slip reduction) which resulted in a downshift...

100SRV