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Trouble code P0492 means:Secondary air injection system (Bank 2)
Troble code P0491 means:Secondary air injection system (Bank 1)
Trouble code P0491 means:Secondary Air Injection System Insufficient Flow (Bank 1)
For 1996 and newer Trouble code P0491 means:Secondary air injection system (bank 1)
The Audi S4 Avant debuted in 2001. In addition, that year Audi launched the Audi A4 (B6) model. Other Audi models were in production, but these 2 launched in 2001.
The 2001 Audi A4 has 20 valves.
The 2001 Audi S8 has 40 valves.
The 2001 Audi A6 has 30 valves.
The 2001 Audi S8 has a V8 engine.
The 2001 Audi A8 has a V8 engine.
The 2001 Audi A8 has 40 valves.
The 2001 Audi S4 has a V6 engine.