4.2.190. SPN 520202, FMI 4, ECU Main Relay 0 short circuit to GROUNDΒΆ

Description

The high and low power outputs of the ECU are supplied via the main relays (the FET transistors). When short circuit to ground or battery is detected, Main relays (MR) will automatically shut off. To ensure whether the short circuit to GND or bat is either temporary or permanent, the MR shall be reactivated after the delay time. If the monitoring system detects a continuous short circuit to ground or bat, the MR will be shut off.

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 (from the high pressure pump) the MPROP wiring terminal surfaces and the pins for possible oxidation in connection surfaces.
  • Measure the high side (hp1) from wiring terminal to the engine ground, to see if there is a short circuit to ground.
  • Measure between the low side (hp 2) from wiring terminal to ECU connector (pin A05), to see if there is a fault cable.
  • Measure between the high side (hp 1) from wiring terminal to ECU connector (pin A04), to see if there is a fault cable.

Solution2:

  • Check the ECU operation with another EEM4 controller. If the system is functional with the replacement ECU, then the original ECU is defective.