Case IH F-4334-00 - ECU – DCU: DEF Pump Pressure Sensor Voltage High

The engine or dosing controller is receiving a voltage signal from the DEF pressure sensor that exceeds the normal operating range. This typically indicates a short circuit to a higher voltage source, an open circuit on the sensor's ground wire, or an internal failure of the pressure sensor itself. Because the sensor is integrated into the DEF pump assembly, a sensor failure usually necessitates replacing the entire pump.

• MAGNUM AFS Connect
• Magnum (180-370)
• Steiger (350-600)
• Maxxum (110-140)
• Puma (130-215)
• Farmall series
• Austoft 9900
• Axial-Flow combines (5130-9230)
• Patriot (4430)
• Titan series

1. 1

   Inspect the wiring harness leading to the DEF Supply Module for chafed wires causing a short to power.

2. 2

   Disconnect the DEF pump connector and check for DEF fluid intrusion (crystallization) or corrosion on the pins.

3. 3

   Verify the 5V reference supply to the UREA pressure sensor from the DCU.

4. 4

   Test the ground circuit for high resistance or an open circuit (an open ground causes the sensor signal voltage to default high).

1. 1

   Power Down

   Turn off the ignition and wait for the DEF system to complete its purge cycle and power down completely (listen for the pump to stop running).

2. 2

   Disconnect

   Disconnect the electrical harness and the DEF fluid lines from the DEF Supply Module. Be prepared to catch minor fluid spills.

3. 3

   Remove

   Unbolt the mounting bracket hardware and remove the faulty DEF Supply Module from the machine.

4. 4

   Install

   Mount the new DEF Supply Module, reconnect the fluid lines securely, and plug in the electrical connector.

5. 5

   Software Reset

   Use the Case IH Electronic Service Tool (EST) to perform an Inducement Counters Reset / engine unlock procedure before returning the machine to service.