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