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 fumed on), which allows for the slight difference between the front and rear driveshafts which nominally occurs when negotiating a comer 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).
- 4x4 HIGH cluster indicator (ground when activated, open circuit when deactivated).

When shifting into or out of LOW range, the GEM requires that the vehicle speed is less than 5 km/hr (3 mph), the brake is applied, and the transmission is in NEUTRAL.

Feature inputs:
- Throttle position information.
- 4WD mode switch.
- Contact plate position inputs A, B. C, D.
- Vehicle speed signal (transmitted from ABS module).
- Brake ON/OFF switch input (battery voltage when brake is depressed, open circuit when not activated).
- Digital transmission range sensor (ground when transmission is in NEUTRAL, open circuit otherwise).
- Start/clutch depressed input (manual transmission only).

Feature outputs:
- 4x4 shift motor relay outputs.
- 4LOW cluster indicators (ground when activated, open circuit when deactivated).
- Solid state clutch relay (pulse width modulated signal; grounded when relay is on, battery potential when relay is off).