New Holland 3426 – ECU: Low Efficiency in DPF Filter

The Diesel Particulate Filter (DPF) is not effectively removing soot and particulate matter from the engine's exhaust. The Engine Control Unit (ECU) monitors DPF efficiency using the DPF differential pressure sensor. When the pressure difference before and after the DPF falls outside the expected range for the current engine load and speed, it indicates the filter is not capturing enough soot or is becoming blocked. Prolonged operation with this fault can lead to a clogged DPF, reduced engine power, and the activation of 'limp mode' to protect the engine.

• T4.120
• T7.175
• T7.190
• T7.210
• Workmaster 33
• Workmaster 37
• Workmaster 50
• Workmaster 60
• Workmaster 70
• Boomer 33
• Boomer 37
• C232
• C238
• B110C
• B95C
• L225
• L230

1. 1

   Check for other active or stored fault codes using a diagnostic scan tool, particularly those related to temperature sensors, NOx sensors, or the EGR system, as these can impact DPF operation

2. 2

   Visually inspect the rubber or metal hoses connected to the DPF differential pressure sensor for cracks, melting, kinks, or soot blockages. Ensure connections are secure at both the sensor and DPF housing

3. 3

   Verify engine operating conditions. Ensure the machine is operated under sufficient load to allow for passive or active regeneration, as frequent light-load operation or excessive idling prevents proper regeneration

4. 4

   Test the DPF differential pressure sensor. Back-probe the connector to verify a 5V reference voltage. At idle, the signal voltage should read between 0.6V and 1.2V and increase with engine RPM. If voltage is stuck, the sensor is likely faulty

5. 5

   Attempt a manual (forced) regeneration using a diagnostic tool in a safe, outdoor location. Monitor DPF soot levels before and after; if regeneration fails or soot does not decrease, the filter may be physically blocked or damaged

1. 1

   Replace DPF differential pressure sensor

   If the sensor fails testing, disconnect the negative battery terminal. Disconnect the electrical connector and pressure hoses, unbolt, and remove the old sensor. Install the new sensor, ensuring hoses connect to the correct inlet and outlet ports. Reconnect the battery, clear fault codes, and test drive.

2. 2

   Remove DPF filter

   If the DPF is blocked and regeneration fails, allow the exhaust system to cool completely. Disconnect attached sensors, remove and discard the securing clamps, support the weight of the DPF, and carefully remove it from the vehicle.

3. 3

   Clean or replace DPF filter

   Send the removed DPF to a specialist for professional cleaning (baking in a kiln) or replace it with a new or remanufactured unit. Reinstall using new clamps and gaskets.

4. 4

   Perform Ash Model reset

   After installing a new or professionally cleaned DPF, use a diagnostic tool to perform an 'Ash Model reset' to inform the ECU that the filter has been serviced.