The ABS pump is a key component in the make up of your anti-lock brake system which watches over your braking activity.
Many drivers would forget the ABS pump exists as it is generally not used on a daily basis. Instead the ABS pump is on standby, waiting for instructions from the ABS system when it senses your wheels are about to lock causing a skid or one wheel is going faster than others. The ABS pump then jumps into action releasing and re-applying pressure to slow the vehicle down. The ABS pump is effectively simulating your foot on a brake pedal but several times a second.
If the ABS pump has gone bad, the ABS warning light or the ESP light would appear. Before you rush out to replace the ABS pump, it is worth getting a qualified mechanic to perform an ABS code reading as the problem could lie with a faulty speed sensor or valve.
The ABS pump can be easily replaced at low cost but it is advisable to use a qualified mechanic.