3.2.273. SPN 520203, FMI 3, ECU Main Relay 2 Short circuit to HIGH SOURCEΒΆ
Description
The high and low power outputs of the ECU are supplied via the main relays (the FET transistors). When a short circuit to ground or battery is detected, the 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 the fan drive operation.
- Measure the voltage between the fan drive (the ECU pin 1.74) and the engine ground, to see if there is a short circuit to bat.