Case IH 3798 – Engine Control Unit (ECU): Diesel Particulate filter Pressure sensor : SRC low for PFlt differential pressure sensor

The engine's control system has detected that the signal voltage coming from the DPF Differential Pressure Sensor is below the minimum acceptable threshold (SRC = Signal Range Check low). This condition typically points to a short circuit to ground in the sensor's wiring, a completely failed sensor, or a severely damaged/disconnected hose line that prevents the sensor from reading exhaust pressure.

• Farmall
• skid steer
• Steiger
• Puma
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)

1. 1

   Visual Hose Inspection: Inspect the differential pressure sensor hoses (the lines connecting the sensor to the upstream and downstream ports of the DPF). Ensure they are not melted, cracked, blocked with soot, or disconnected.

2. 2

   Wiring & Connector Check: Inspect the wiring harness and the electrical connector at the DPF differential pressure sensor for corrosion, bent pins, or wire chafing that could cause a short to ground.

3. 3

   Voltage Test: Verify that the ECU is sending the correct 5-volt reference and ground to the sensor.

4. 4

   Live Data Monitoring: Use the Case IH Electronic Service Tool (EST) to monitor the sensor's output voltage. If the voltage remains stuck low regardless of engine RPM/exhaust flow, the sensor or circuit is dead.

1. 1

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

2. 2

   Locate the DPF differential pressure sensor, which is typically mounted on a bracket near the exhaust aftertreatment/DPF assembly.

3. 3

   Carefully disconnect the electrical harness connector from the sensor.

4. 4

   Disconnect the two pressure hoses from the sensor.

   Mark the hoses (upstream vs. downstream) so they are not swapped during reinstallation.

5. 5

   Remove the mounting bolts securing the sensor to its bracket and remove the faulty sensor.

6. 6

   Install the new DPF differential pressure sensor and secure it with the mounting hardware.

7. 7

   Reconnect the pressure hoses to their respective ports and plug in the electrical connector.

8. 8

   Reconnect the battery.

9. 9

   Connect the Case IH EST (or a compatible diagnostic scanner) to clear the 3798 fault code.

10. 10

    Run the engine and, if prompted by the ECU, perform a stationary DPF regeneration to reset the soot load model and verify the sensor is reading differential pressure correctly.