P0411 OBD II Trouble Code Secondary Air Injection System Incorrect Flow Detected

Detailed information on troubleshooting and repairing a P0411 DTC code which has to do with the secondary air injection system. Also includes links to relevant forum topics on the code.

Symptoms of P0411 OBD II Trouble Code

  • MIL (Malfunction Indicator Lamp) illumination
  • Backfiring in the exhaust under hard acceleration
  • Engine running rich (This is counter-intuitive. See explanation below)
  • Squealing belt

Common Causes of P0411 OBD II Trouble Code

  • Damaged or missing check valve
  • AIR pump intake port plugged/damaged
  • AIR pump clutch malfunction
  • Holes or damage to exhaust components