ABS, EPC, TC, Engine Light fixed if removing rear light bulb (Solved)


New Member
Hello everyone!

I've been fixing my A2 now 2 years in. Cause time apparently don't grow on trees.
It all started with someone thinking it was a good idea to change just one out of two timing belts.
Had it standing at my brother for a year, "outside" before I had time and place to fix it.

Engine runs fine when cold but triggers ENGINE, ABS, TC, EPC after a while and gets a ruff idle until it settles for 1100 and I can't rev the engine anymore. Notice a weak rear light, maybe just a bad ground to the rear light. Got new lights bulbs just to be sure its not just the bulbs. Lights works fine now, still same engine problem / ABS lights. Disconnected the rear light left and right just to check (Middle still connected). Engine now runs like it should and throws just EPC after 3km trip. Engine idles just fine.
Disconnect the brake light switch instead. Same results as disconnecting the rear light. Disconnected the ABS module to see if that was the issue but did no difference.
Tried a new brake light switch but did no difference.

Can't see any damage on the cables I looked at so far.

17912 Air intake system leak detected <-- goes away then I remove rear brake bulb
17961 Altitude sensor signal/intake manifold pressure Implausible ratio <-- goes away then I remove rear brake bulb
01314 Engine Control module

This sounds similar but I can fix it with removing the rear brake bulbs.


New Member
Did the throttle calibration just to eliminate some kind of fault, and now everything works just fine. So cleaning or touching the throttle body without calibrating might trigger many interesting faults. I will keep posted if the faults stay away or come back.


New Member
Going to try to explain what I was told.

So if the throttle body is cleaned the car notice this as a vacuum leak. This is why you will have an engine light. Since the abs has the ability to control the throttle body this will also be triggered by this error cause the car will not respond in the expected way.

So doing a throttle calibration is VERY important after cleaning. Cause everything connected to the throttle body will go nuts.

Hope this helps someone in the future.