Audi Workshop Service and Repair Manuals

The secondary air system is designed to enable the catalytic converter to heat up and reach its operating temperature more quickly after a cold start.

Principle of operation

Due to the extra mixture enrichment during the cold-start phase, an increased amount of unburnt hydrocarbons is carried in the exhaust gas. The secondary air system improves the afterburning (oxidation) process in the catalytic converter, and in this way reduces toxic emissions. The heat generated by oxidisation accelerates the "light off" of the catalytic converter and significantly improves exhaust gas quality during warm-up.

• Secondary air pump relay -J299
• ◆ Location => Fig. 26-42
• Engine control unit -J220
• Cylinder head
• Secondary air inlet valve
  -N112
• ◆ Location => Fig 26-41
• Brake servo
• Non-return valve
• ◆ Installation position (light side/ dark side) as shown in illustration. Arrow indicates direction of flow
• Combination valve for secondary air system
• ◆ Location => Fig. 26-42
• ◆ Removing and installing
  

• Air cleaner
• Secondary air pump motor -V101
• ◆ Location => Fig. 26-41
• Intake manifold

→ Fig.1    Location of secondary air inlet valve

-N112

• ◆ Installation location: rear left side on bulkhead -arrow-.

→ Fig.2    Location of secondary air pump motor

-V101

• ◆ Fitting location: front right of engine compartment below alternator or A/C compressor

→ Fig.3    Location of secondary air pump relay

-J299

• ◆ Fitting location: under cover on left side of bulkhead

•     1 -    Relay for secondary air pump -J299
•     2 -    Voltage supply relay for Motronic -J271

→ Fig4    Location of combination valve for secondary air system

• ◆ Installation location: left on cylinder head