Case IH F-4334-01 - ECU – Engine Control Module (ECM): DEF / AdBlue Pressure Sensor Voltage Below Normal

The DEF (Diesel Exhaust Fluid) / AdBlue pressure sensor voltage is below normal or lower than expected. This means the sensor is returning a voltage signal to the controller that falls below the acceptable operational range. This condition is typically caused by a short circuit to ground, an open circuit in the sensor wiring, a failure of the 5V sensor power supply, or a completely failed pressure sensor.

• MAGNUM AFS Connect
• Magnum (180 through 370)
• Steiger (350 through 600)
• Maxxum (110 through 140)
• Puma (130 through 215)
• Axial-Flow 5130
• Axial-Flow 6130
• Axial-Flow 7130
• Axial-Flow 7230
• Axial-Flow 8230
• Axial-Flow 9230
• Patriot 4430
• Titan series
• Farmlift series

1. 1

   Visually inspect the DEF supply module and wiring harness for physical damage, rodent damage, or severe urea crystallization (white crust) which can cause electrical shorts.

2. 2

   Test the electrical harness at the DEF supply module connector. Verify that Pin 2 is receiving a steady 5V from the ECM and that Pin 4 has a solid ground.

3. 3

   Check Pin 3 (pressure sensor signal) for a short to ground or an open circuit.

4. 4

   Ensure there are no external leaks in the DEF lines that would prevent the system from building pressure (though a voltage code usually points to electrical issues).

1. 1

   Clean the area

   Thoroughly clean the area around the DEF supply module with distilled water to remove any dried urea crust and dirt. Do not let debris fall into the fluid loops.

2. 2

   Disconnect power

   Turn off the machine and disconnect the battery to prevent electrical spikes.

3. 3

   Repair wiring harness

   If the diagnostic checks revealed a short to ground or broken wire in the harness leading to Pins 2, 3, or 4, repair the damaged wiring and re-test.

4. 4

   Replace DEF supply module

   If the wiring is intact and the 5V supply is present, the pressure sensor itself has failed. On Bosch Denoxtronic systems, the sensor is integrated internally and cannot be serviced separately. Replace the entire DEF Supply Module.

5. 5

   Replace DEF filter

   If replacing the module, or servicing an older module, use the specialized extraction tool to remove and replace the internal DEF supply module filter. Be careful not to scratch the inner walls of the pump housing.

6. 6

   Reassemble and clear codes

   Reconnect the fluid lines and electrical harness. Reconnect the battery, use a diagnostic scan tool to clear the F-4334-01 / SPN 4334 code, and run a manual DEF dosing test to verify system pressure.