Indicates that front oxygen sensor (at the input of catalytic converter) detects higher than expected percentage of oxygen in exhaust gasses. Could be due to the unbalanced air-to-fuel proportion at the engine, fault oxygen sensor or other systems.


  • Check Engine dashboard light is ON
  • Possible lack of power and car dynamic
  • Unstable work and sound from engine: stumbles, shakes


  • Faulty or dirty mass air fuel (MAF) sensor
  • Malfunctioning fuel pump
  • Clogged fuel filter or injectors
  • Vacuum leak
  • Faulty oxygen sensor
  • Leaks in exhaust system

Severity - moderate

Does not have immediate danger effect to the car or driver, but at longer period could lead to engine overheating and damage. .


  • Check and clean MAF sensor
  • Inspect vacuum and air intake systems for leaks
  • Inspect and replace, if required, fuel filter
  • Inspect and replace, if required, fuel pump
  • Review and correct, if required, fuel injectors, exhaust system, other systems that have DTCs.