CAR OBD CODES

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

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.

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

• 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

• 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.