New Holland 3427 – Engine ECU: DPF Flow Resistance Low

The Engine Control Unit (ECU) has detected low flow resistance through the Diesel Particulate Filter (DPF). The differential pressure sensor is reporting an abnormally low pressure difference between the DPF inlet and outlet. This indicates that exhaust gas is passing through the filter with less restriction than expected, which typically points to a compromised filter element (cracked or missing), leaking sensor hoses, or a failure in the differential pressure sensor circuit.

• T4.85
• T4.95
• T4.105
• T4.115
• T5.95
• T5.105
• T5.115
• TD5.85
• TD5.95
• TD5.105
• TD5.115
• Workmaster 33
• Workmaster 37
• Boomer 33
• Boomer 37

1. 1

   Examine the pressure differential sensor hoses for any cracks, splits, disconnections, or signs of heat damage.

2. 2

   Visually inspect the entire DPF assembly and the upstream Diesel Oxidation Catalyst (DOC) for visible cracks, melting, leaks, or excessive deposits.

3. 3

   Check for water ingress in the differential pressure sensor by gently tapping it with the pressure ports facing down.

4. 4

   Verify sensor voltage with key on/engine off: check for a 5-volt reference supply, a good ground (0 volts), and a signal wire voltage between 0.6 and 0.8 VDC at atmospheric pressure.

5. 5

   Perform a pressure test with the engine running: pressure differential at idle should be around 0.5-1.5 psi. Revving the engine should cause a corresponding increase in both the pressure reading and the sensor's signal voltage.

1. 1

   Address hose leaks

   If cracks or leaks are found in the DPF pressure hoses during diagnostic checks, replace them and ensure connections are secure. Clear the fault code and operate the machine to see if the code returns.

2. 2

   Replace DPF differential pressure sensor

   If hoses are in good condition but the sensor fails voltage or pressure response tests, disconnect the electrical connector and pressure hoses (noting port orientation). Remove the mounting bolts, install the new sensor, and reconnect. Clear fault codes and verify live data is within the expected range.

3. 3

   Inspect and replace DPF internals

   If the sensor and hoses are confirmed good, remove the DPF canister from the exhaust system. Inspect internally for cracks or signs of light passing directly through the filter media. If damage is found, replace the DPF assembly.

4. 4

   Perform forced regeneration

   After any repair is completed, perform a forced DPF regeneration using a diagnostic service tool to verify that the entire system is operating correctly under load and high temperatures.