4.2.254. SPN 521001, FMI 4, DEF heater main relay open circuitΒΆ

Description

EEM4 monitoring system has detected open load on DEF heater main relay.

Possible causes are:

  • The DEF heater main relay wiring is defective.
  • The DEF heater main relay is defective

Reaction in EEM

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

NOTE: The present fault is classified as an emission related fault. Engine power will be reduced after a certain time defined by an authority.

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 DEF heater main relay wiring, the connectors and the contact surfaces of the connector pins (possible oxidation).
  • Check the operation with another DEF heater main relay to see if the main relay is defective.