CAN Bus Messages
The CAN bus is a high speed broadcast network connected between various vehicle control modules. It allows the fast exchange of data between control modules every few microseconds. The bus comprises two wires, which are twisted together to minimize electromagnetic interference (noise) produced by the CAN messages. Refer to Communications Network article.
The electronic rear differential control module is connected on the CAN bus, via the transfer box control module, and controls differential operation using CAN messages from other control units on the network. Wheel speed, steering angle, automatic transmission speed, temperature information, car configuration, axle ratios and mode inputs, are some of the main signals received by the control module.
The control module also sends messages via the CAN bus to tell other control modules on the network, the status of the electronic rear differential. The clutch torque and default mode status are some of the main signals sent out by the control module.
The following table shows the messages that can be displayed in the message center of a high-line instrument cluster relating to the electronic rear differential:
| Message | Description | Chime |
|---|---|---|
| 'TRANSMISSION OVERHEAT' 'SLOW DOWN' |
Rear differential temperature has reached or is approaching the overheat threshold. | None |
| 'TRANSMISSION FAULT' 'TRACTION REDUCED' |
Transfer box control module has stopped transmitting CAN bus messages. Defaults to open center differential. Message also displayed when fault occurs with electronic rear differential. |
None |
| 'TRANSMISSION FAULT' 'STOP SAFELY' |
Fault has occurred with electronic rear differential. Stop vehicle at earliest opportunity. | Single |
On vehicles fitted with the low line instrument cluster, in place of the message center there will be a status lamp, which has the following logic:
- Amber - Over temperature
- Red - Failure, stop vehicle