Explorer 4WD V6-245 4.0L SOHC VIN K SFI (2001)
Control Module: Description and Operation
The A4WD system is an electrostatic shift 4x4 system that allows the operator to choose between three different 4x4 modes. The operator can switch
between A4WD and 4WD HIGH modes at any speed. To engage or disengage LOW range the vehicle speed must be less than 5 km/h the brake
depressed and the transmission must be in NEUTRAL.
The front/rear driveshaft speed sensors (Hall effect) are mounted to the transfer case and detect the speed of the front and rear driveshafts. This input is
used by the generic electronic module (GEM) primarily to control A4WD operation.
The throttle position output signal is provided to the GEM from the powertrain control module (PCM). This signal is used by the GEM in controlling the
A4WD clutch.
The shift motor sense plate an integral part of the electric shift motor informs the GEM to the position of the transfer case.
The digital TR sensors are located on the LH side of the transmission; these sensors inform the GEM when the transmission is in the neutral position.
The electric shift motor is mounted externally at the rear of the transfer case. It drives a rotary cam which moves the mode fork and range fork within the
transfer case between the HIGH range (A4WD 4HIGH) and LOW range positions.
The 4x4 shift motor uses a module containing two relays which under the control of the GEM shifts the transfer case shift motor between HIGH range
(A4VVD 4HIGH) and 4LOW modes.
The solid state clutch relay is used to activate the A4WD clutch within the transfer case.
System Function
Hall effect sensor monitors input and output shaft speed.
In the A4WD (C-Trac) system the GEM varies the torque sent to the front driveline by controlling the transfer case clutch. At rest and under cruising
conditions the GEM activates the transfer case clutch a minimum duty cycle (percentage of time the clutch is turned on) which allows for the slight
difference between the front and rear driveshafts which normally occurs when negotiating a corner on dry pavement. Under any of the following
conditions the GEM will increase the duty cycle in order to prevent or control slip:
^ Slip is detected (by using the Hall Effect Sensors)
^ Heavy acceleration (throttle position).
Feature inputs:
^ Brake ON/OFF switch.
^ 4WD mode switch.
^ Digital transmission range sensor.
^ Clutch switch (manual transmission vehicles only).
^ Vehicle speed signal (transmitted from the ABS module).
^ Front/rear driveshaft speed sensors.
^ Throttle position information from the PCM.
^ Contact plate position inputs A B C D.
Feature outputs:
^ Solid state clutch relay (pulse width modulated signal: grounded when relay is on battery potential when relay is off).
^ A4WD indicator (ground when activated open circuit when deactivated).
^ 4x4 shift motor relay outputs.
Shifts between A4WD and 4x4 HIGH can be made at any speed. Listed below are the inputs and outputs needed by the GEM to execute a change
between any of these modes. Feature inputs:
^ Front/rear driveshaft speed sensor.
^ Vehicle speed signal.
^ Throttle position information.
^ 4WD mode switch.
Feature outputs:
^ Solid state clutch relay (pulse width modulated signal; grounded when relay is on battery potential when relay is off).
