2018 A4 2.0T Rough Idle and CEL Flashing

ClearTheCode guidance (Audi · Engine & drivetrain)

Summary: For 2018 A4 2.0T Rough Idle and CEL Flashing, work through these steps on your 2016+ vehicle:

1. Confirm the symptom — note when it happens (cold start, highway, after fuel fill, etc.).
2. Scan codes — save all pending/stored DTCs; don't clear until you've recorded them.
3. Check TSBs & recalls — look up your VIN for open campaigns and known fixes.
4. Inspect the obvious — related fuses, connectors, fluid level, and recent repairs.
5. Test the common fix — follow model-specific service procedures; one change at a time.
6. Escalate if needed — burning smell, no brakes, overheating, or stalling in traffic → shop visit.

Owner reported: My 2018 Audi A4 2.0T Premium Plus has been acting up lately. It started with a slight rough idle, but now it's pretty noticeable, especially at stop lights. The check engine light came on and occasionally flashes, which I know is serious.

I've also noticed a slight decrease in fuel economy and the car just doesn't feel as smooth as it used to. I'm worried about driving it like this, especially wi…

This is educational guidance, not a substitute for hands-on diagnosis.