General Description

Electronic Controls System Information

General Description
In order to understand and diagnose transfer gearbox control system related problems, a complete understanding of the range shift control process is necessary.

The TCU receives and transmits information to and from:
1. Shift Control Motor Position Switch
2. High/Low Request Switch
3. Transfer Gearbox Speed Sensor
4. Drivers selected range on the H-Gate
5. GEMS ECM
6. Automatic Transmission Control Module (TCM)
7. The BeCM Using this information the TCU energizes an electric motor to shift ranges in the transfer gearbox. Study the block diagram (Figure 1) to understand the relationships between the various components in the transfer gearbox shift control system.

The information received by the TCU from the shift control motor encoder switches regarding the motor's position and from the driver's selected range results in the following:
- Movement of the shift control motor from one range to another.
- Information to the driver through the Message Centre and H-Gate illumination.