Models with higher performance level came fitted with ABS.
The principle of operation is the same as on cars with conventional braking systems but the layout is much simpler as all we need to control the operating pressure of the brakes are a few electro-valves.
We've all seen this readout once or twice in the life of our XM. Rectifying the problem is not always simple although possible. Here we deal with another side of the issue: the display itself. While the ABS is actually out of use for any reason, this warning is very intrusive on the dot matrix display, practically preempting it and masking most other information messages like open doors, radio stations and similar.
The most likely cause is intermittent connection to a sensor (or possibly an intermittently failing sensor) which is OK with the car level and the wheels in the straight ahead position, but which breaks when wheels are turned or the body tilts.
Measure the impedance of each ABS sensor coil on each wheel with all possible combinations of suspension at maximum and minimum level and steering turned fully to the left and right. If that doesn't work, you could try detaching each sensor from the wheel and gently flexing the cable.