Air Injection: Description and Operation

Secondary air system, function/components

The secondary air system permits faster warm-up and thus makes the catalytic converter ready for operation sooner after cold starting.

Principle
Due to over-enrichment of the mixture in the cold start phase, there is an increased amount of unburned hydrocarbons in the exhaust gas. The injection of secondary air improves the oxidation in the catalytic converter and thus reduces emissions. The heat produced by secondary oxidation reduces start-up time for the catalytic converter therefore improving the emission quality in the cold-running phase.

Function
^ During the cold running phase, the engine control module -6- actuates the secondary air injection pump -1- via the secondary air injection pump relay 5-. Air reaches the combination valve for the secondary air inlet -3-.
^ Parallel to this the secondary air inlet valve -8- is actuated, which allows the vacuum to reach the combination valve for secondary air inlet -3. The combination valve for secondary air inlet thus allows the secondary air to enter the exhaust ducts of the cylinder head -9-.





1. Secondary Air Injection (AIR) Pump motor -V101-
^ Location Fig. 2
2. Air cleaner
3. Combination valve for secondary air inlet
^ Location: Fig. 4
4. Non-return valve
^ Position(light side/ dark side or direction of arrow) as shown in illustration, arrow faces in direction of flow
5. Secondary Air Injection (AIR) Pump relay -J299-
6. Engine Control Module -J220-
7. Vacuum reservoir
^ Location: In front left wheel housing beneath wheel housing liner
8. Secondary Air Injection (AIR) Solenoid valve -N112-
^ Location Refer to, Fig. 1.
9. Cylinder head





Fig. 1 Installation position Secondary Air Injection (AIR) valve -N112-
^ Location: below intake pipe
1 - Recirculating valve for turbocharger -N249- (green connection)
2 - Secondary air injection valve -N112- (brown connection)

Note: The illustration shows bottom view of intake pipe.





Fig. 2 Installation position for Secondary Air Injection (AIR) Pump motor -4101-
^ Front right in engine compartment beneath air filter housing





Fig. 3 Installation position Secondary Air Injection (AIR) Pump relay -J299-
^ In E-box in plenum chamber
1 - Engine control module
2 - Secondary air pump relay -J299-
3 - Power supply relay for Motronic -J271-
4 - Fuse S130 for secondary air pump





Fig. 4 Combination valve for secondary air injection
^ Right rear on cylinder head