E 350 Van V8-7.3L DSL Turbo VIN F (1995)
Anti-Lock Brake System Module: Description and Operation
Four Wheel Anti-Lock Brake System (4WABS)
PURPOSE
The antilock brake electronic control module monitors the brake on/off switch and the system speed sensors to determine when the antilock brake
system should be engaged.
In addition, the electronic control module provides a speed signal to the Programmable Speedometer/Odometer Module (PSOM).
DESCRIPTION
It is an on-board diagnostic, non-repairable unit consisting of two microprocessors and necessary circuitry for their operation. These
microprocessors are programmed identically. The antilock brake electronic control module monitors system operation during normal driving as
well as during antilock braking.
OPERATION
Under normal driving conditions, the microprocessors produce short test pulses to check the electrical system without any mechanical reaction.
The antilock brake electronic control module continuously monitors the speed of each wheel to determine if any wheel is beginning to lock. When
a wheel locking tendency is detected, the antilock brake electronic control module signals the appropriate solenoid valve in the antilock hydraulic
control unit to open or close as well as the pump motor to turn on and recycle brake fluid back to the brake master cylinder. This results in
moderate pulsations of the brake pedal and pump noise which may be heard in the passenger compartment. During normal braking, the brake pedal
feel will be identical to a standard brake system.
Most concerns which occur to the antilock brake system will be stored as a coded number in the Keep-Alive Memory (KAM) of the antilock brake
electronic control module. This means that once a code is stored, it will be retained by the antilock brake electronic control module even with the
key in the OFF position. The codes can be retrieved by following the on-board diagnostic procedures.
