Secondary air system: Principle
Due to over-enrichment of the mixture during the cold start phase, there is an increased amount of un-combusted 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 pump -3-. Air reaches the combination valves for Secondary Air Injection (AIR) -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 (AIR) -5- and -9-. The appropriate combination valve for Secondary Air Injection (AIR) thereby opens the path for secondary air to the exhaust channels of the cylinder head.
NOTE:
The following list refers to items in Fig 1.
- Secondary Air Injection (AIR) pump relay -J299-
- Removing and installing, see SECONDARY AIR INJECTION (AIR) SOLENOID VALVE -N112-, REMOVING AND INSTALLING
- Checking, see SECONDARY AIR INJECTION (AIR) PUMP RELAY -J299- AND ACTIVATION, CHECKING
- Motronic Engine Control Module (ECM) -J220-
- Combination valve for secondary air injection (AIR)
- Secondary Air Injection (AIR) solenoid valve - N112-
- Installation position, see INSTALLATION LOCATION OF SECONDARY AIR INJECTION (AIR) SOLENOID VALVE -N112-
- Secondary Air Injection (AIR) pump motor -V101-
- Installation position, see INSTALLATION POSITION OF SECONDARY AIR INJECTION (AIR) PUMP MOTOR -V101-
- Check valve
- Installation position (light/dark side): Arrow points in direction of flow, as shown in figure.
- To intake manifold
- Combination valve for secondary air injection (AIR)
- Vacuum reservoir
- Installation location: Under wheel housing liner in wheelhousing