Functional Operation

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 transmission to go into "limp-in" or "default" mode. While in this mode, the TCM may not energize some of the solenoids in the transmission.

The only transmission functions that may be available are:
^ Park and Neutral
^ Reverse
^ Fourth Gear (Clear Selector OD Position)
^ Third Gear (Gear Selector 3 Position)
^ First Gear (Gear Selector 1-2 Position)

Depending on the DTC that is set, determines what gear(s) are allowed. If one or more of the transmission solenoids are shorted to voltage or stuck open (therefore appearing energized to the transmission), the transmission may be stuck in the gear that would normally be engaged when a particular solenoid is energized.

The following chart shows the solenoid status required for a particular gear to be engaged.





Although vehicle performance may be seriously degraded while in this mode (limp-in), it allows the owner to drive the vehicle in for service.