P1157: Lack Of HO2S22 Switch - Sensor Indicates Lean
MediumPowertrainO2 Sensors
What does P1157 mean?
P1157 is a diagnostic trouble code indicating "Lack Of HO2S22 Switch - Sensor Indicates Lean". The engine is running with too much air relative to fuel (lean condition). This can cause hesitation, rough idle, and potential engine damage if left unaddressed. The o2 sensors needs attention.
Common causes
- Vacuum leak (intake gasket, hose, or PCV valve)
- Weak or failing fuel pump
- Clogged fuel injectors
- Dirty or faulty mass airflow (MAF) sensor
- Exhaust leak before the O2 sensor
What should you do?
Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.
Get a diagnosis for YOUR car
Code P1157 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.