OBD-II FAULT CODE
P1138

Lack Of HO2S12 Switch - Sensor Indicates Rich

Reference information for P1138. Because this is manufacturer-specific, confirm the exact definition for the vehicle before using the diagnostic guidance below.

Manufacturer-specific code

This code can have different meanings depending on vehicle make, model and year. Treat the definition below as a reference and confirm it with OEM service information before diagnosis or repair.

PowertrainSystem
Fuel trim / rich conditionCategory
MediumSeverity
  • Check Engine light
  • Poor drivability or reduced fuel economy depending on fault
  • Poor fuel economy
  • Fuel smell
  • Black smoke in severe cases
  • Leaking injector
  • Faulty fuel pressure regulator
  • Contaminated MAF/MAP reading
  • EVAP purge stuck open
  • Scan all modules and record freeze-frame data before clearing codes
  • Check battery voltage and related fuses
  • Check fuel trims, fuel pressure, injector leak-down and purge valve operation
  • Repair leaking injector/pressure issue, clean/replace faulty airflow sensor, repair purge system fault
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Disclaimer: Information is provided for general guidance only and may not apply to all vehicles. Always consult a qualified technician.