3.2.223. SPN 4344, FMI 31, DEF supply module heater ECU power stage over temperatureΒΆ

Description

The EEM4 monitoring system has detected over temperature on the DEF supply module heater ECU power stage.

Possible causes are:

  • The DEF supply module heater relay wiring is defective.
  • The DEF supply module heater is defective.
  • The control unit 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 which is 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 supply module heater relay wiring, the connectors and the contact surfaces of the connector pins (possible oxidation). (see Supply module)
  • Check the operation with another DEF supply module heater relay to see if the relay is defective.
  • Check the ECU operation with another EEM4 controller. If the system is functional and the fault is not active with the replacement ECU, then the original ECU is defective.