Emission Control Systems: Description and Operation

2000 Volkswagen Jetta Sedan (9M2) V6-2.8L (AFP)SECTION Description and Operation



Secondary Air System
Function
During a cold start (+15°C to +35°C coolant temperature), the secondary air system blows air behind the exhaust valve for 65 seconds. This enriches the exhaust with oxygen, and starts after-burning, thereby reducing the catalytic converter warm-up phase. Control passes from the engine control unit 0220) across the air injector reaction pump relay 0229) to the secondary air valve (N 112, switch-over valve) and combination valve. In addition, on every subsequent start of the engine (up to a maximum engine temperature of 851C), the secondary air system will idle for 5 seconds after a delay of about 20 seconds and the self-diagnosis is run.

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.