3.2.361. SPN 520393, FMI 19, ECU 1 CAN C Bus OffΒΆ

Description

The EEM4 system is not be able to communicate through the ancillary CAN 2 bus.

Possible causes are:

  • A control unit malfunction on the CAN bus.
  • There are too many/few terminating resistors on the CAN bus.
  • The CAN bus wiring is defective.
  • A poor connection.

In the 3,4,6 and 7 cylinder engines the CAN C bus is an ancillary bus and it is connected to

  • the 2.17 and the 2.18 ECU pins

In the V12 engines the CAN C bus is a private bus connected to the ECU 2. The pins in the ECU 1 are

  • the 2.17 and the 2.18 ECU pins

Reaction in EEM

The FC is stored and the warning lamp is activated. The CAN message indicates active fault.

Solution

First save the error log and then erase it. Restart the ECU after erasing the error log. If the fault occurs again during the next driving cycle, check the following paths:

  • Check the CAN bus for a short circuit or an open load on the CAN bus.
  • Check the ECU connectors and the contact surfaces of the connector pins (possible oxidation).
  • Check the ECU operation with another EEM4 controller. If the system is functional and the fault is not active with the replacement ECU, then the original ECU is defective.