Sensor Block

The sensor block is mounted on the left side of the booster/master cylinder assembly and contains several electrical components critical to operation of the ABS. Included in the sensor block assembly are the pressure monitoring module (which controls pump operation and provides a low pressure warning), the valve relay (which provides power to the solenoid valves) and electrical connections for the valve block, booster piston travel switches and the control pressure switch.

The sensor block also provides the connection point at which the main harness attaches to the hydraulic unit. All communication between the EBCM and the hydraulic unit takes place through the sensor block. The sensor block is a serviceable component. The following connectors are included on the sensor block:

• Control Pressure Switch (2-pin, on front of sensor block)
• Reed Block (2-pin, on booster/master cylinder assembly)
• Valve Block (12-pin, behind sensor block cover)
• Sensor Block Main Harness Connector (15-pin, on top of sensor block)
• Hydraulic Unit Ground (single pin, on top of sensor block below the control pressure switch connector)

The sensor block also contains the following electrical components which are critical to system operation:

1. Valve Relay
   
   The valve relay is contained in the sensor block and provides power to the 5 solenoid valves. When the valve relay is not energized, it provides a path to ground for the valve circuits of the valve block and plunger unit. The EBCM controls the valve relay through an input to the sensor block pressure monitoring module. The valve relay is energized during normal operation.
2. Pressure Monitoring Module
   
   The pressure monitoring module controls pump operation, by grounding the pump relay coil, in response to changes in hydraulic accumulator pressure. The pressure monitoring module contains 2 pressure switches; if these switches do not indicate the same pressure, the sensor block will turn on the Red BRAKE warning lamp and disable anti-lock function. The pressure monitoring module will also turn on the BRAKE lamp and disable the anti-lock (by turning off the valve relay) if low accumulator pressure is detected.