Air Injection: Testing and Inspection

Secondary Air System







The Secondary Air Injection (AIR) system causes the catalytic converter to heat up more quickly, resulting in earlier operating readiness following cold start.

Principle

Due to over-enrichment of the mixture during the cold start phase, there is an increased amount of uncombusted carbon monoxide in the exhaust. Secondary Air Injection (AIR) improves secondary oxidation in the catalytic converter and therefore reduces emissions. The heat produced by secondary oxidation greatly reduces start-up time for the catalytic converter, therefore improving exhaust quality during the cold start phase significantly.







Function
- In the cold start phase, the ECM -4- activates the secondary air pump -2- via the relay for secondary air injection -3-. Air reaches the combination valves for secondary air injection -5- and -9-.
- The Secondary Air Injection (AIR) valve -6- is activated in parallel, which allows the vacuum to reach the combination valves for secondary air injection -5- and -9-. The appropriate combination valve for secondary air injection thereby opens the path for secondary air to the exhaust channels of the cylinder head.

1. From air filter housing
2. Secondary Air Injection (AIR) pump motor -V101-
- Component location, see fig. 2.
3. Secondary Air Injection (AIR) pump relay -J299-
- Component location, see fig. 3.
4. Motronic Engine Control Module (ECM) -J220-
5. Combination valve for secondary air injection (right)
- Component location, see fig. 4.
- Checking
6. Secondary Air Injection (AIR) solenoid valve -N112-
- Component location, see fig. 1.
7. Check-valve
- Installed position (light/dark side): Arrow points in direction of flow, as shown in figure.
8. To Intake manifold
9. Combination valve for secondary air injection (left)
- Component location, see fig. 4.
10. Vacuum reservoir
- Installed location: Under wheel housing liner in left front wheel housing







Fig. 1 Component location Secondary Air Injection (AIR) solenoid valve -N112-

- Bolted to holding plate for solenoid valves at rear of engine (arrow).







Fig. 2 Secondary Air Injection (AIR) pump motor -V101-

- At front right in engine compartment below air filter housing

1. Secondary Air Injection (AIR) pump motor -V101-
2. Electrical harness connector for Secondary Air Injection (AIR) pump motor -V101-







Fig. 3 Secondary Air Injection (AIR) pump relay -J299-

- In E-box, plenum chamber

3. Secondary Air Injection (AIR) pump relay -J299-
B. Fuse for secondary air pump -S130-







Fig. 4 Combination valve for Secondary Air Injection (AIR)

- At rear of cylinder heads

NOTE: Right valve is shown in illustration.