Means you have to take it to the shop to get the ABS checked!!! The brakes will continue to work in stopping the Expy, it is just that the ABS will not work properly.
A short primer on ABS: Speed sensors located at each wheel look at a gear type target to see if the wheel is turning. While driving, each wheel should be turing at or about the same speed (there will be a difference between the front wheels while turning). While the wheels, and thus the gear target, are turning, the sensor will generate pulses (as each gear tooth passes over the sensor). The ABS system monitors these pulses. When braking, if one of these pulse streams stops, or decreases a significant amount (like when the wheel locks up during an emergency stop causing a loss of traction), the ABS will activate to regain traction by releasing the brake pressure to that particular wheel brake caliper. This pressure release is usually in the form of pulses, which is what most people feel and equate with the ABS action.
To ensure the system is working, the ABS system performs diagnostics upon startup, and as I stated above, monitors the pulse stream from each sensor. I believe that if the ABS system loses a pulse stream while the brakes are NOT activated, it concludes as one type of error that a sensor has failed. I think that this may be what is wrong, but this is only a guess. This needs to be checked by a qualified shop, as this complicated system is usually beyond the "backyard mechanic".
In any case, when the ABS system "fails", the brakes simply revert to the "old style" brake system, fully functional, except that you will have to take over the ABS function yourself and feather the brakes during an emergency, or on ice/leaves/water/etc., to make sure you don't lock them up.
In my case, that is how I learned to drive, so I am not sure if my ABS has ever been activated. I have been programmed to do this already!!
I hope this helps.
