ABS Sensors
 

Hi can anyone tell me what sensors the ABS uses on the W124 platform, I believe their are wheel sensors (is it all 4?) but are any other factors read by the controlling unit such as Engine RPM?

Would not think engine rpm has much to do with it because system has to work regardless of what gear car is in.

If you are having trouble with your brakes, like a pulsating brake pedal when it should not pulsate, try cleaning the sensors that are located in the front axle assembly. A few years ago mine began pulsating. I removed the sensors and cleaned them. They pick up the metal particles from the pads and rotors and eventually get entirely covered. There are probably sensors in rear - I don't remember.