Audi A4 2009–2012 — technical service bulletin
Bulletin 01138320330011 · NHTSA communication 10228360 · issued Mar 29, 2013
Technical service bulletin
communication type
Engine and Engine Cooling
component
2009–2012
model years
12
vehicle entries
Official summary
Under certain driving conditions, the secondary air ports in the cylinder head can accumulate carbon over time, causing a restriction.
Vehicles covered
What a TSB means. Technical service bulletins are repair guidance manufacturers send to dealers — they are not recalls, and repairs are not automatically free (warranty extensions are an exception worth checking). The full document is available via NHTSA’s vehicle lookup.