2.2.277. SPN 520201, FMI 19, CAN BUS: CAN B Bus Off (Private)ΒΆ

Description

The EEM monitoring system is not be able to communicate through the private CAN bus.

Possible causes are:

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

In the 3,4,6 and 7 cylinder engines the CAN B bus is a private bus and it is connected to

  • the 1.71 and the 1.95 ECU pins

In V12 engines the CAN B bus is an ancillary bus connected to

  • the 1.71 and the 1.95 ECU pins

Reaction in EEM

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

NOTE: This does not affect the inline engine normal function because the engine CAN is only used for the R&D.

Solution

First save the error log and then do the procedure that follows:

  • 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).