Electronic Automatic Gearbox Interface - From 99MY

The ECM communicates with the EAT ECU via a Controller Area Network (CAN). This is used for the gearshift torque interface and as a means for transmitting OBD information between the two control units. The EAT ECU passes OBD data and requests to the ECM which controls the storage of diagnostics data and MIL activation. Unlike the GEMS ECM, the Bosch M5.2.1 does not store gearbox faults. The MIL activation request can be checked with Testbook.

The CAN network is a high speed serial interface operating at 500 k-baud. The system is a differential bus using a twisted pair. If either or both wires of the twisted pair CAN bus is open or short circuited, a CAN time out fault will occur and the EAT ECU defaults to third gear.

See AUTOMATIC GEARBOX, Description and operation.