4.2.324. SPN 729, FMI 4, Grid heater voltage below normalΒΆ

Description

The measured grid heater voltage is below the normal operating range.

Possible causes are:

  • The grid heater wiring is defective (Shorted to ground.)
  • The gird heater relay is defective
  • The grid heater 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 grid heater wiring, the connectors and the contact surfaces of the connector pins (possible oxidation). (see Grid heater solenoid)
  • Check the grid heater relay operation. Measure the relay output voltage.
  • Check the operation with another grid heater to see if the heater is defective.