FITMENT
Compatible with Volkswagen Group diesel vehicles equipped with SCR (Selective Catalytic Reduction) AdBlue emission systems requiring NOx monitoring.
Common applications include:

• Audi A4 (B8 / B9 diesel SCR variants depending on engine)
• Audi A5 (diesel SCR variants)
• Audi S4 / S5 (select diesel SCR applications where fitted)
• VW Passat (B7 / B8 diesel SCR variants)
• VW Sharan (diesel SCR variants 2010+)
• Related VW Group 2.0 TDI / 3.0 TDI SCR platforms

Using reference numbers:

• 03L907807AD (OEM VAG part number)
• 5WK9 6688A (Continental/VDO sensor cross-reference)
• Common SCR NOx sensor family used across Audi/VW/Seat/Skoda systems

This sensor is part of the SCR exhaust aftertreatment system and monitors nitrogen oxide (NOx) levels to control AdBlue dosing and ensure emissions compliance.

FAQ
Q1: What is the function of this NOx sensor?
A1: It measures nitrogen oxide (NOx) in the exhaust and sends real-time data to the ECU to control AdBlue injection and reduce emissions.

Q2: Where is it installed?
A2: It is installed in the SCR exhaust system, typically before or after the catalytic converter depending on vehicle configuration.

Q3: What are symptoms of failure?
A3: Check engine light, SCR/AdBlue warnings, NOx sensor fault codes, reduced engine power, or limp mode activation.

Q4: Are 03L907807AD and 5WK9 6688A interchangeable?
A4: Yes, 03L907807AD is the OEM VAG reference and 5WK9 6688A is the supplier cross-reference for the same NOx sensor unit, but correct fitment depends on engine code and ECU calibration.