Audi Workshop Service and Repair Manuals

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

Principle

On account of the overenrichment of the mixture in the cold start phase the percentage of unburnt hydrocarbons in the exhaust gas is higher. The injection of secondary air improves the post-oxidation in the catalytic converter and thus reduces pollutant emissions. The heat liberated by the post-oxidation considerably shortens the start-up time of the catalytic converter and significantly enhances the emission quality in the cold-running phase.

Function

• ◆ In the cold-running phase the engine control unit -3- actuates the secondary air pump -1- via the secondary air injection relay -2-. Air is routed to the combi valves for secondary air injection -4- and -8-.
• ◆ In parallel with the above the secondary air injection valve -5- is actuated therefore allowing vacuum to reach the combi valves for secondary air injection -4- und -8-. The appropriate combi valve for secondary air injection thus permits the passage of secondary air to the exhaust ducts of the cylinder head.

• Secondary air pump motor
  -V101
• Secondary air pump relay -J299

• Engine control unit -J220
• Combi valve for secondary air induction
• Secondary air inlet valve
  -N112
• Non return valve
• ◆ Note installation position (light side/ dark side): As shown in Fig, arrow faces in direction of flow
• To intake manifold
• Combi valve for secondary air induction
• Vacuum reservoir
• ◆ Location: In front left wheel housing beneath wheel housing liner