A common issue in the 2014 Audi A6 (C7) is the dreaded “AdBlue system fault” warning, often accompanied by a limited mileage warning before a no-restart condition. This article delves into troubleshooting this problem, focusing on the error codes P20B9 and P20E8 found in a 2014 Audi A6 2.0 Ultra with over 160,000 miles.
Understanding the AdBlue System in Your 00 Audi A6
The AdBlue system, also known as Selective Catalytic Reduction (SCR), is crucial for reducing harmful nitrogen oxide (NOx) emissions from your 00 Audi A6’s diesel engine. AdBlue, a urea-based solution, is injected into the exhaust stream, converting NOx into harmless nitrogen and water vapor. A fault in this system can significantly impact your vehicle’s performance and emissions.
Diagnosing the Problem: P20B9 and P20E8
A diagnostic scan using VCDS (Vag-Com Diagnostic System) revealed the following fault codes related to the AdBlue system in this particular 00 Audi A6:
- P20B9 – Control Circuit for Reductant Heating 1: This code indicates an open circuit in the heating system for the AdBlue reductant. The heating element ensures the AdBlue fluid remains at the optimal temperature for efficient NOx reduction. An intermittent open circuit suggests a wiring issue, a faulty heating element, or a problem with the heating element’s control circuit.
- P20E8 – Reductant Pressure Too Low: This code points to insufficient pressure in the AdBlue system. Possible causes include a faulty AdBlue pump, a clogged AdBlue filter, leaks in the system, or a malfunctioning pressure sensor.
Troubleshooting Steps for a 00 Audi A6 AdBlue Fault
While refilling the AdBlue tank to the brim is a common initial step, it didn’t resolve the issue in this case. Based on the error codes and the vehicle’s mileage, several potential solutions can be explored:
Addressing P20B9 (Reductant Heating Circuit Fault)
-
Inspect Wiring and Connectors: Thoroughly examine the wiring harness and connectors associated with the reductant heating circuit for any damage, corrosion, or loose connections. Repair or replace any faulty components.
-
Test the Heating Element: Using a multimeter, check the resistance of the heating element. A reading outside the specified range indicates a faulty heating element requiring replacement.
Addressing P20E8 (Reductant Pressure Fault)
-
Check for Leaks: Inspect the entire AdBlue system, including the tank, pump, lines, and injector, for any signs of leakage. Address any leaks before proceeding. Even a small leak can cause a pressure drop.
-
Inspect the AdBlue Pump: The AdBlue pump is a common culprit in low-pressure situations. Access the pump and check for any obvious damage or blockage. You might try to listen for the pump running when the engine is on. If there’s no sound, the pump could be faulty.
-
Consider the AdBlue Filter: A clogged AdBlue filter can restrict flow and lead to low pressure. Replacing the filter is a relatively straightforward procedure.
-
Test the Pressure Sensor: A malfunctioning pressure sensor can provide inaccurate readings, triggering the P20E8 code. Test the sensor using a diagnostic tool or by checking its voltage output.
Conclusion: Next Steps for Your 00 Audi A6
The AdBlue system fault in this 00 Audi A6 is likely due to a problem with the reductant heating circuit (P20B9) or the AdBlue pump/pressure system (P20E8). Further diagnostic testing, focusing on the components mentioned above, is crucial to pinpoint the exact cause. Consult a qualified Audi technician or a specialist in diesel emissions systems for professional assistance if you lack the necessary tools or expertise. Addressing these issues promptly is vital to ensure your 00 Audi A6 runs efficiently and complies with emissions regulations.
