Explorer 2WD V6-245 4.0L (1994)
4WABS Control Module: Description and Operation
PURPOSE
The ECU monitors system operation during normal driving as well as during anti-lock braking.
OPERATION
Under normal driving conditions, the microprocessors produce short test pulses to check the electrical system without any mechanical reaction.
The ECU continuously monitors the speed of each wheel to determine if any wheel is beginning to lock. When a wheel locking tendency is
detected, the ECU signals the appropriate solenoid valve in the hydraulic control unit to open or close as well as the pump motor to turn on and
recycle brake fluid back to the 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 anti-lock brake system will be stored as a coded number in the Keep-Alive Memory (KAM) of the ECU. This
means that once a code is stored, it will be retained by the ECU even with the key in the OFF position. The codes can be retrieved by following the
on-board diagnostic procedures. Refer to Diagnosis and Testing.
CONSTRUCTION
It is an on-board diagnostic, non-repairable unit consisting of two microprocessors and the necessary circuitry for their operation. These
microprocessors are programmed identically.
LOCATION
The Electronic Control Unit (ECU) is located in the engine compartment behind the driver's side headlamp on a bracket mounted on the surface of
the plastic fender apron.
