The A4WD system is an electronic 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 (A4WD, 4HIGH), and 4LOW modes.
The solid state clutch relay is used to activate the A4WD clutch within the transfer case.
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Tuesday, January 11th, 2011 AT 12:14 PM