A common issue with Volkswagen TDI engines is the “Mileage to Reducing Agent Deficiency” warning, often accompanied by a countdown to when the car won’t start. This warning usually indicates a problem with the AdBlue (DEF) system, requiring a Vcds Scr Reset. This article will guide you on how to potentially reset this countdown using a VCDS diagnostic tool.
Understanding the AdBlue System and the Need for a VCDS SCR Reset
The AdBlue system is crucial for reducing harmful NOx emissions in diesel engines. When a fault occurs, such as low pressure in the AdBlue injection system, the car’s computer initiates a countdown. Once this countdown reaches zero, the engine won’t start to prevent further emissions. A common fault code associated with this issue is P20E8 (Reductant Pressure Too Low). While the underlying problem requires repair, a temporary solution might involve a VCDS SCR reset to extend the countdown and allow you to drive the vehicle until a proper fix can be implemented.
Performing a VCDS SCR Reset: Exploring Options
One method suggested for a VCDS SCR reset involves using the “Long Adaptation” function within the VCDS software. However, this option isn’t always available in all VCDS versions or for all vehicle models. If you don’t see “Long Adaptation,” you can try resetting the “SCR Lock” and other SCR-related settings in “Basic Settings.”
Unfortunately, resetting these settings doesn’t always resolve the “Mileage to Reducing Agent Deficiency” warning or reset the countdown. This is because the underlying fault triggering the warning needs to be addressed.
Troubleshooting and Considerations for a VCDS SCR Reset
If the basic VCDS SCR reset procedures don’t work, further diagnostics are necessary. The fault code, like the P20E8 mentioned earlier, offers clues to the root cause. In the example provided, the fault indicates low pressure, suggesting a potential issue with the AdBlue pump or pressure sensor.
Examining the freeze frame data from the VCDS scan can provide more details. Key parameters to check include:
- Pressure sensor for reducing agent: measured pressure: A reading of 0 hPa indicates a significant pressure problem.
- Reducing agent pump: activation: This shows if the pump is working.
- Reducing agent injector: activation: This indicates if the injector is functioning.
Addressing the Root Cause
Ultimately, a VCDS SCR reset is a temporary workaround. To permanently resolve the issue, the underlying fault must be repaired. This might involve replacing the AdBlue pump, pressure sensor, or other components within the AdBlue system.
Conclusion
While a VCDS SCR reset might temporarily extend the drive time before the car is immobilized, it’s crucial to remember that it doesn’t fix the underlying problem. Using VCDS to diagnose the fault codes and freeze frame data is essential to pinpoint the issue and ensure proper repair. Consult a qualified mechanic or VW specialist for accurate diagnosis and repair of your AdBlue system.
