Audi Workshop Service and Repair Manuals

Principle and function Principle Because of the over-enrichment of the mixture in the cold start phase, the proportion of unburned hydrocarbons in the exhaust gas is higher. The secondary air system improves the afterburning (oxidation) process in the catalytic converter, and thus 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.

Function

t	During the warm-up phase, the engine control unit -4- activates the secondary air pump -3- via the secondary air pump relay -2-.Air will then reach the combination valves for secondary air system -5- and -9-.

t	At the same time, the secondary air inlet valve -6- is actuated, thus allowing vacuum to reach the combination valves for secondary air system -5- and -9-. In this way, the combination valve opens a passage for the secondary air system to supply air to the exhaust ports in the cylinder head.

1 -	From air cleaner housing

2 -	Secondary air pump motor -V101-

q	Fitting location → Fig.

q	Removing and installing → Chapter

3 -	Secondary air pump relay -J299-

q	Fitting location → Fig.

4 -	Motronic control unit -J220-

5 -	Combination valve for secondary air system (right-side)

q	Fitting location → Fig.

q	Checking → Chapter

q	Removing and installing → Chapter

6 -	Secondary air inlet valve -N112-

q	Fitting location → Fig.

7 -	Non-return valve

q	Installation position (light side/dark side) as shown in illustration. Arrow indicates direction of flow.

8 -	To intake manifold

9 -	Combination valve for secondary air system (left-side)

q	Fitting location → Fig.

q	Checking → Chapter

q	Removing and installing → Chapter

10 -	Vacuum reservoir

q	Fitting location: in front left wheel housing beneath liner

Fitting location of secondary air inlet valve -N112- t  Bolted to retainer plate for solenoid valves at rear of engine -arrow-.

Fitting location of secondary air pump motor -V101- t  At front right of engine compartment, below longitudinal member. 1 -  Secondary air pump motor -V101- 2 -  Electrical connector for secondary air pump motor -V101-

Fitting location of secondary air pump relay -J299- t  In electronics box (plenum chamber) 2 -  Secondary air pump relay -J299- B -  Secondary air pump fuse -S130-

Fitting location of combination valve for secondary air system t  At rear of cylinder heads.   Note Illustration shows valve on right side.