U 520243

Massey Ferguson U 520243 – Engine Controller (EEM4) / SCR dosing control unit: Urea level plausibility error: Signal not plausible

Issue description

The control system is receiving an erratic, out-of-range, or illogical reading from the Diesel Exhaust Fluid (DEF) / AdBlue tank level sensor.

Verify the actual fluid level in the DEF tank and ensure the fluid is clean, as contamination can trigger sensor faults.
Inspect the DEF tank cap and breather to ensure dust and moisture are not entering the tank.
Inspect the urea fluid sensor wiring harness, checking the power supply and terminal circuits for open circuits, shorts to ground, or corrosion at the connector.
Connect a diagnostic scan tool to observe live data from the Urea Tank Level Sensor to see if the signal is stuck, dropping out, or reading empty when full.

Clean the Area
Before opening the DEF system, thoroughly clean the area around the DEF tank header. The system is highly sensitive to contamination; treat the tank neck as 'spotless'.
Drain the Tank
If fluid contamination is suspected, drain the DEF tank completely and flush it with distilled water or fresh DEF.
Disconnect Power
Turn off the machine and disconnect the battery to prevent electrical shorts.
Remove the Sensor
Disconnect the electrical harness from the DEF level sensor/header assembly. Carefully unbolt and remove the sensor unit from the top of the DEF tank.
Install the New Part
Insert the new DEF level sensor/header assembly into the tank, ensuring the O-ring or gasket is properly seated to prevent leaks and air ingress.
Reassemble and Refill
Bolt the sensor down, reconnect the electrical harness, and reconnect the battery. Refill the tank with fresh, high-quality 32.5% urea DEF/AdBlue.
Clear Codes
Use a diagnostic scan tool to clear the U 520243 fault code and verify that the live level reading is now plausible and accurate.

(2)

DEF Level Sensor / Urea Tank Header Assembly
4351064M2
The DEF level sensor is often integrated into the DEF tank header unit, which also houses the DEF temperature sensor and fluid pickup tubes. Match the specific part number to your machine's serial number via an AGCO parts catalog.
4351064M2

DEF Level Sensor / Urea Tank Header Assembly
4355030M2
The DEF level sensor is often integrated into the DEF tank header unit, which also houses the DEF temperature sensor and fluid pickup tubes. Match the specific part number to your machine's serial number via an AGCO parts catalog.
4355030M2

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