Four Wheel Drive System Operation - Electronic Shift on the Fly (ESOF): Notes

(2H) OPERATION

When the MSS is in 2WD (2H), power is delivered to the rear wheels only. This mode is appropriate for normal on-road driving on dry pavement and provides the best fuel economy. Torque is passed through the transfer case to the rear drive shaft at a 1:1 ratio. In 2WD (2H):

The MSS sends a 2WD (2H) mode status to the TCCM via a hardwired connection.

The TCCM provides a ground for the IWE solenoid (IWE_OS # = No).

The TCCM outputs a 0% duty cycle to the synchronization clutch field coil (4WD_CLTCH_OUT # = 0.00%).

The shift motor is in the full CCW position. Refer to TRANSFER CASE

(2H) will momentarily be displayed in the message center at key up and after a 4WD (4H) to 2WD (2H) shift.

NOTE: When shifting to (2H) mode in order for the IWEs to completely disengage the vehicle steering wheel must be less than 90 deg and 5 seconds have elapsed since the shift to (2H) has been initiated.

(4H) OPERATION

When 4WD (4H) is selected on the MSS, the 4WD system provides mechanically locked four-wheel drive with power delivered to all four wheels, for increased traction. 4WD (4H) is for use in off-road or winter conditions such as deep snow, sand or mud. This mode is not for use on dry pavement.

Shifts from 2WD (2H) to 4WD (4H) can be made at any speed. When performing this shift, release the accelerator pedal prior to the shift and wait until the Shift in Progress message disappears in the IPC before accelerating. This improves the shift performance as the transfer case and IWEs engage. To engage 4WD (4H):

The MSS sends a 4WD (4H) mode status to the TCCM via via a hardwired connection.
The TCCM outputs a 0% to 97% duty cycle to the synchronization clutch field coil (4WD_CLTCH_OUT # = x.xx%).
The shift motor rotates CW to the 4WD (4H) position. Refer to TRANSFER CASE
The TCCM outputs a 0% duty cycle to the synchronization clutch field coil (4WD_CLTCH_OUT # = 0.00%).
The TCCM opens the ground for the IWE solenoid (IWE_OS # = Yes).
4WD (4H) is displayed in the message center.

(4L) OPERATION

(4L) 4WD provides mechanically locked four-wheel drive power to both the front and rear wheels for use on low traction surfaces, but does so with an additional 2.64 gear reduction for increased torque multiplication. Intended only for off-road applications such as deep sand, steep grades or pulling heavy objects. 4WD (4L) does not engage when your vehicle is moving above 3 mph (5 km/h); this is normal and should be no reason for concern.

Shifts to and from 4WD (4L) can only be made below 3 mph with the transmission in Neutral. When performing this shift, wait until the 4x4 Shift in Progress message disappears in the IPC before moving the selector lever back to Drive. If the vehicle speed or transmission range is not within parameters, the message center will indicate the necessary action needed to complete the shift.

In (4L):

The MSS sends a 4WD (4L) mode status to the TCCM via a hardwired connection.
The TCCM opens the ground for the IWE solenoid (IWE_OS # = Yes).
The TCCM outputs a 0% duty cycle to the synchronization clutch field coil (4WD_CLTCH_OUT # = 0.00%).
The shift motor rotates to the full CW position. Refer to 4HI-LOC Torque On Demand Transfer Case Shift Motor
4WD (4L) is displayed in the message center.

ESOF Transfer Case Shift Motor

Vehicles equipped with the Electronic Shift on the Fly (ESOF) system use a shift motor to enter and exit 2WD (2H), 4WD (4H), and 4WD (4L) modes.

The electric shift motor is mounted externally to the transfer case. It drives a rotary cam which moves the mode and range forks within the transfer case. The shift motor moves during shifts between 2WD (2H), 4WD (4H), and 4WD (4L). The TCCM directly controls the electric shift motor and can reverse motor polarity to reverse rotary cam/shift fork direction. The message center may display "Shift in Progress" while the shift motor is operating. The shift motor sense plate, an integral part of the shift motor assembly, informs the TCCM of the transfer case position. The sense plates are a set of 4 contacts that are opened and closed to represent each valid transfer case shift motor position. The mode and range forks are spring loaded so the motor can move to position regardless of the time it takes it takes for the transfer case internal shaft and hub splines to align and engage.

ESOF Transfer Case Shift Motor Status

Position	PLATE_A	PLATE_B	PLATE_C	PLATE_D
(2H)	Closed	Open	Closed	Closed
(4H)	Open	Closed	Closed	Open
(4L)	Open	Closed	Open	Closed
Neutral	Closed	Closed	Open	Open