John Deere 3251.04 – Engine Control Unit (ECU): DPF Differential Pressure Signal Out of Range Low

The voltage signal from the Diesel Particulate Filter (DPF) differential pressure sensor is below the expected level. This sensor measures the pressure difference between the DPF inlet and outlet to determine soot accumulation. A falsely low reading can cause the Engine Control Unit (ECU) to incorrectly assume the DPF is clean, preventing necessary regeneration cycles. Over time, this can lead to a clogged DPF, reduced engine performance, potential engine damage, and symptoms like limp mode, sluggish acceleration, rough idling, or stalling.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5090M
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 204L
• 304L
• 6105M
• 8R Series (8245R to 8400R)
• 9RT Series (9470RT, 9520RT, 9570RT)
• 7400A TerrainCut
• 7500A
• 7700A
• 8000A E-Cut Hybrid
• Graders
• Excavators

1. 1

   Inspect Sensor Tubes: Remove the pressure tubes/hoses connecting the sensor to the DPF. Check them for soot blockage, condensation buildup, or cracks. Blocked lines can skew pressure readings.

2. 2

   Inspect Wiring and Connectors: Check the sensor plug and wiring harness for corrosion, loose pins, or chafing. You are specifically looking for an open circuit or a short to ground.

3. 3

   Test Sensor Voltages: Using a multimeter, check the DPF differential pressure signal circuit. Verify that the sensor is receiving the correct reference voltage (VREF) and that the signal ground (SIG GND) is intact.

4. 4

   Verify ECU Data: Use diagnostic software (like John Deere Service ADVISOR) to compare live pressure readings with actual exhaust flow.

1. 1

   Clean or replace sensor tubes

   If the diagnostic checks reveal soot or condensation in the sensor tubes, thoroughly clean them out or replace them if they are cracked or melted.

2. 2

   Repair wiring or replace connector

   If a short to ground or open circuit is found in the harness, repair the damaged wire or replace the corroded connector pigtail.

3. 3

   Replace the DPF differential pressure sensor

   If the wiring, voltages, and tubes are all in good condition but the sensor output voltage remains out of range (stuck low), the sensor itself has failed internally and must be replaced.

4. 4

   Re-calibrate and perform forced regeneration

   After replacing the sensor or repairing the circuit, clear the fault codes. It is highly recommended to perform a forced stationary DPF regeneration to verify the repair, ensure the sensor reads correctly under load, and clear any soot that accumulated while the system was in a derated state.