2.2.376. SPN 639, FMI 19, CAN BUS: CAN A Bus Off (Powertrain)ΒΆ

Description

The EEM monitoring system is not able to communicate with other ECUs through the powertrain 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.

The CAN A bus is a powertrain bus connected to:

  • the 1.46 and the 1.47 ECU pins

Reaction in EEM

The FC is stored and the warning lamp is activated. The EEM4 controller will start to use the hardwired throttles for speed control. In case there are no hardwired throttles, the engine runs at low idle speed.

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.
  • If a vehicle connector is used, check the wiring from the ECU to the vehicle connector.
  • Check the connectors and the contact surfaces of the connector pins (possible oxidation).