3.2.371. SPN 521001, FMI 4, DEF heater relay shorted to groundΒΆ

Description

The EEM4 monitoring system has detected a short circuit on the DEF heater main relay control circuit.

Possible causes are:

  • The DEF heater main relay wiring is defective. (Shorted to ground.)
  • 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.

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 relay is defective.