Servotronic Transducer Valve The Servotronic transducer valve is located in a port on the side of the steering rack valve housing. The valve is sealed in the housing with an O-ring seal and is secured with two long screws into threaded holes in the housing. The Servotronic valve is a transducer controlled valve which responds to control signals supplied from the Body Control Unit (BCU). The BCU contains a microprocessor which receives road speed signals from the ABS ECU and calculates the correct controlling signal for the Servotronic valve. The Servotronic software within the BCU has a diagnostic capability which allows TestBook/T4 to check the tune of the steering. The Servotronic valve determines the hydraulic reaction at the steering rack rotary valve and controls the input torque required to turn the steering wheel. The Servotronic system allows the steering to be turned with minimum effort when the vehicle is stationary or manoeuvred at slow speed. The hydraulic reaction changes proportional to the vehicle speed, with the required steering effort increasing as the vehicle moves faster. At high speeds, the Servotronic system provides the driver with a good feedback through the steering providing precise steering and improved stability. A major advantage of the Servotronic system is that fluid pressure and flow through the rotary valve remains constant and allows full steering pressure to be available in an emergency where a sudden and unexpected steering correction maybe required.