Controller Area Network (CAN) System

Controller Area Network (CAN) System
The controller area network (CAN) system is a high speed serial interface between the ECM and the Electronic Automatic Transmission (EAT) ECU. The CAN system uses a 'data bus' to transmit information messages between the ECM and the EAT ECU. Because there are only two components in this CAN system, one will transmit information messages and the other will receive information messages, and vice-versa.

Conditions
The CAN system is used by the EAT ECU and the ECM for transmission of the following information:
^ Gearshift torque control information.
^ EAT OBD information.
^ MIL request.
^ Vehicle speed signal.
^ Engine temperature.
^ Engine torque and speed.
^ Gear selected.
^ Gear change information.
^ Altitude adaptation factor
^ Air intake temperature
^ Throttle angle/pedal position

Function
The CAN system uses a twisted pair of wires to form the 'data bus' to minimise electrical interference. This method of serial interface is very reliable and very fast. The information messages are structured so that each of the receivers (ECM or EAT ECU) is able to interpret and react to the messages sent.

The CAN 'data bus' is directly connected between pin 36 of connector C0637 of the ECM and pin 16 of connector C0193 at the EAT ECU, and pin 37 of connector C0637 of the ECM and pin 44 of connector C0193 at the EAT ECU.

The CAN system can fail in the following ways:
^ CAN data bus wiring open circuit.
^ CAN data bus wiring short circuit.

In the event of a CAN data bus failure any of the following symptoms may be observed:
^ MIL illuminated after 2 drive cycles (NAS only).
^ EAT defaults to 3rd gear only.
^ Harsh gearshifts.
^ 'Sport' and 'manual' lights flash alternately.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook.