A recent DPF cleaning and refitting on a 1.6 TDI engine resulted in a persistent DPF light and limp mode, despite performing a forced regeneration using VCDS. This article explores the diagnostic process and troubleshooting steps taken, along with the remaining issues encountered.
VCDS Diagnostic Scan Results
A VCDS scan revealed the following fault codes after the DPF cleaning and refitting:
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16856 – Particle Filter (P2463): Excessive Soot Accumulation. This fault indicates a significant buildup of soot within the DPF, triggering the MIL (Malfunction Indicator Lamp). Freeze frame data showed a soot mass measured (MASS_SOOT_PHY_PF) of 40.00g.
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14356 – Exhaust Gas Temperature Sensor 4 Bank 1 (P246E): Electrical Malfunction. This fault, appearing after the forced regeneration attempt, suggests a problem with the exhaust gas temperature sensor.
Forced Regeneration Procedure
Following the Ross-Tech wiki guide for Diesel Particle Filter Emergency Regeneration on 1.6l/2.0l R4 & 3.0l V6 CR-TDI (UDS) engines, a forced regeneration was initiated using VCDS. The “Service regeneration of particulate filter while driving” adaptation channel was used due to the unavailability of the “Service regeneration of particle filter” option.
Monitoring Regeneration Progress
During a 45-minute test drive, advanced measuring blocks were used to monitor the following:
- IDE00434: Soot mass remained constant at 54.60g.
- IDE00435: Soot mass decreased from 75.12g to 11.63g. This suggests the regeneration process was partially successful in reducing soot levels.
Persistent Issues
Despite the observed decrease in soot mass (IDE00435), the DPF light remained illuminated, and the vehicle stayed in limp mode. Furthermore, the measured soot mass (MASS_SOOT_PHY_PF) in the engine scan remained unchanged at 40.00g, contradicting the observed decrease in IDE00435.
Replacing the exhaust gas temperature sensor with a new one did not resolve the issue, and relearning the sensor via basic settings also proved ineffective.
Remaining Questions and Troubleshooting
The discrepancy between the decreasing soot mass observed in IDE00435 and the static value of MASS_SOOT_PHY_PF raises questions about the accuracy of the sensor readings or a potential issue with the DPF control module. Further investigation is required to pinpoint the root cause of the persistent DPF light and limp mode. Possible areas to explore include:
- Verifying the proper functioning of the DPF pressure sensor.
- Checking for any exhaust leaks that could affect regeneration.
- Inspecting the DPF for any physical damage or blockage.
- Consulting with a qualified technician specializing in VW/Audi diagnostics.
