ANTI-LOCK BRAKE SYSTEM TROUBLESHOOTING AND TESTING - CONTINUED
ABS MODULATOR VALVES - CONTINUED
NOTE: The valves will cycle in 1-2-3-4 order, then diagonally in 1-2 and 3-4 order
Figure 2. Modulator Valve Checking.
ABS sensor systems consist of a tooth wheel mounted on the hub of each monitored wheel and a sensor installed so that
its end is against the tooth wheel. The sensor continuously sends wheel speed information to the ECU. A sensor clip
holds the sensor in place at the tooth wheel.
The type of axle determines the sensor mounting location:
Steering axle sensors are installed in the steering knuckle or in a bolted-on bracket.
Drive axle sensors are mounted in a block attached to the axle housing or in a bolted-on bracket.
The ECU is the brain of the ABS system. It receives information from the sensors and sends signals to the ABS valves
A tooth wheel (Figure 3) is mounted at the hub of each sensed wheel, with a sensor installed so that its end is against the
tooth wheel. A sensor clip holds the sensor in place at the tooth wheel. The sensor and clip must be greased with Rock-
well WABCO-recommended lubricant.