4.2.251. SPN 521000, FMI 8, DEF pump temperature signal duty cycle in failure rangeΒΆ

Description

The measured DEF pump temperature signal duty cycle is in failure range.

Possible causes are:

  • The DEF supply module wiring is defective. (Shorted to high source or an open circuit.)
  • The DEF supply module is defective.

Reaction in EEM

The FC is stored and the warning lamp is activated. The CAN message indicates active fault. The SCR system might be unable to dose and the engine will derate when the emissions are exceeded due to the SCR system malfunction.

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