When a diesel particulate filter (DPF) becomes excessively clogged, a forced regeneration using VCDS (Vag-Com Diagnostic System) might be necessary. This article discusses a specific case study of a Vcds Force Regen attempt on a 1.6l TDI engine and the troubleshooting steps taken when the initial regeneration didn’t resolve the issue.
Understanding the Problem: Initial Diagnosis and Force Regen Attempt
After a DPF cleaning and refitting, a vehicle continued to experience issues. A VCDS scan revealed the following fault codes:
- 16856 – Particle Filter P2463 00 [175] – Excessive Soot Accumulation: This code confirms excessive soot buildup in the DPF, triggering the malfunction indicator lamp (MIL) and potentially causing limp mode.
- Freeze Frame Data: The freeze frame data captured at the time of the fault provides valuable information such as engine RPM, load, speed, temperatures, and pressure readings. Critically, it showed “Particle filter: soot mass measured-MASS_SOOT_PHY_PF: 40.00 g.”
Following the Ross-Tech wiki guide for Diesel Particle Filter Emergency Regeneration for UDS engines, a forced regeneration was initiated using Adaptation Channel “Service regeneration of particulate filter while driving” due to the unavailability of the “Service regeneration of particle filter” option.
During a 45-minute test drive, measuring blocks IDE00434 (calculated soot mass) and IDE00435 (measured soot mass) were monitored. IDE00434 remained constant at 54.60g, while IDE00435 decreased from 75.12g to 11.63g. Despite this decrease, the DPF light remained on, and the vehicle stayed in limp mode. The “Particle filter: soot mass measured” value in the engine scan also didn’t change from 40.00g.
Further Troubleshooting Steps
Following the unsuccessful force regen, additional steps were taken:
- New Sensor: A new exhaust gas temperature sensor was installed, but it reported the same values as the original sensor. This ruled out a faulty sensor as the primary cause.
- Basic Settings Relearn: A basic settings relearn procedure was performed via VCDS, but it didn’t resolve the problem.
- New Fault Code: A new fault code, 14356 – Exhaust Gas Temperature Sensor 4 Bank 1 P246E 00 [167] – Electrical Malfunction, appeared after the forced regen and test drive. This suggests a potential issue with the exhaust gas temperature sensor circuit, which could be affecting the DPF regeneration process.
Potential Causes and Solutions
The persistent DPF light and limp mode, despite the observed decrease in measured soot mass during the forced regen, suggest several possible causes:
- Faulty Exhaust Gas Temperature Sensor Circuit: The new fault code related to the exhaust gas temperature sensor points to a potential problem with the sensor’s wiring, connector, or the sensor itself. Thoroughly inspecting the circuit for damage or corrosion is crucial.
- DPF Pressure Sensor Issues: While not directly indicated in the fault codes, a faulty DPF pressure sensor could be providing inaccurate readings, preventing the system from recognizing a successful regeneration.
- DPF Regeneration Control Issues: There might be a problem with the engine control module (ECM) or its software, hindering the proper execution of the regeneration process. Checking for ECM software updates is recommended.
- Blocked DPF: Although the DPF was cleaned, there’s a possibility it wasn’t cleaned effectively or that a blockage has reoccurred.
Conclusion: Next Steps
This case highlights the complexities of DPF issues and the need for thorough diagnostics. The next steps should involve:
- Inspecting the exhaust gas temperature sensor circuit: Address the P246E fault code by checking wiring, connectors, and sensor functionality.
- Checking the DPF pressure sensor: Inspect the sensor and its wiring for any issues.
- Consulting with a qualified technician: A professional with expertise in diesel engine diagnostics and DPF systems can perform more advanced troubleshooting and repairs. Using specialized tools, they can analyze live data streams during a forced regen attempt to pinpoint the root cause.
