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.