General Information

GENERAL DESCRIPTION
The AW4 electronic transmission in a conventional transmission in that it uses hydraulically applied clutches to shift a planetary gear train. However, the electronic control system replaces many of the mechanical and hydraulic components used in conventional transmission valve bodies.

FUNCTIONAL OPERATION
The AW4 system performs it's functions based on continuous real-time sensor feedback information. The Transmission Control Module (TCM) continuously checks for electrical problems, some mechanical problems, and some hydraulic problems. When a problem is sensed, the TCM stores a diagnostic trouble code. Some of these codes cause the transaxle to go into "limp-in" or "default" mode. While in this mode, the TCM will not energize any of the solenoids in the transmission, and the only transmission functions are:
- Park and Neutral
- Reverse
- Fourth Gear (Gear Selector OD Position)
- Third Gear (Gear Selector 3 Position)
- First Gear (Gear Selector 1-2 Position)

There is one exception to the preceding statement. If one or more of the transmission solenoids are shorted to voltage or stuck open (therefore appearing energized to the transmission), the transmission will be stuck in the gear that would normally be engaged when a particular solenoid is energized. See chart below.

Sol #1 Sol #2 Gear
Off On 1st
On On 2nd
On Off 3rd
Off Off 4th

No upshifts or downshifts are allowed. The position of the manual valve alone allows the ranges that are available. Although vehicle performance is seriously degraded while in this mode, it allows the owner to drive the vehicle in for service.