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Principle and functionBecause of the over-enrichment of the mixture in the cold startphase, the percentage of unburned hydrocarbons in theexhaust gas is higher. The injection of secondary air improvesthe post-oxidation in the catalytic converter and thus reducespollutant emissions. The heat produced by the post-oxidationconsiderably shortens the start-up time of the catalyticconverter and significantly enhances the emission quality inthe cold-running phase.

In the cold-running phase the engine control unit -J623--Item 4- activates the secondary air pumpmotor -V101--Item 2- via the secondary air pump relay -J299--Item 3-. Air will then reach thecombination valves for secondary air system -5- and -9-.

At the same time, the secondary air inlet valve -N112--Item 6- will be activated, allowing vacuumpressure to reach the combination valves for secondary air system -5- and -9-. In this way, thecombination valve opens a passage for the secondary air system to supply air to the exhaust ports inthe cylinder head.

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1 - From air cleaner housing

2 - Secondary air pump motor -V101-

Fitting location Fig.

Removing and installing Chapter

Check using vehicle diagnosis, testing and information system -VAS 5051 A- in the function GuidedFault Finding

3 - Secondary air pump relay -J299-

Fitting location Fig.

Check using vehicle diagnosis, testing and information system -VAS 5051 A- in the function GuidedFault Finding

4 - Engine control unit -J623-

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

Fitting location Fig.

Checking Chapter

Removing and installing Chapter

6 - Secondary air inlet valve -N112-

Fitting location Fig.

Check using vehicle diagnosis, testing and information system -VAS 5051 A- in the function GuidedFault Finding

7 - Non-return valve

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 (left-side) Fitting location Fig.

Checking Chapter

Removing and installing Chapter

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10 - Vacuum reservoir

Fitting location: in front left wheel housing beneath liner

Fitting location of secondary air inlet valve -N112-

Inserted on retainer plate for solenoid valves at rearof engine -arrow-.

Fitting location of secondary air pumpmotor -V101-

On longitudinal member (right-side, bottom) -arrow-.

Fitting location of secondary air pumprelay -J299- and secondary air pump fuse-S130-

In electronics box (plenum chamber,passenger's side).

1 - Secondary air pump relay -J299-

B -Secondary air pump fuse -S130-

(50 amp)

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Combination valve for secondary air

At rear of cylinder heads.

Note

Illustration shows valve on right side.