P1138

P1138 OBD Code Definition:
P1138 Lack Of HO2S12 Switch – Sensor Indicates Rich

P1138 OBD Code Description

Lack Of HO2S12 Switch – Sensor Indicates Rich is one of the Definitions for the P1138; however your vehicle’s manufacturer may have a different Definition for the P1138 code.

Possible Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

Possible Solutions

  • Check Mass Air Flow (MAF) Sensor
  • Check Fuel Pressure Regulator
  • Check Fuel Pump
  • Check Intake/Exhaust System for Leaks
  • Check Secondary Air Injection for Leaks
  • Check Vacuum Lines for Leaks

Tech Notes

  • Fuel Trim Info
  • When this fault is stored and external vacuum leaks are not found, less obvious problems may be present:
    • Check Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80)
    • Check Brake Booster and Hoses
    • Check Electric Vacuum Pump ( If Applicable )
    • Check Crankcase Ventilation System for faulty components. When the PCV or Crankcase Ventilation System is faulty, vacuum is typically present under the oil cap and misfire faults are common.

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