P1156 — Lack Of HO2S21 Switch - Sensor Indicates Lean

What it means

P1156 is an OBD-II diagnostic trouble code: Lack Of HO2S21 Switch - Sensor Indicates Lean.

Typical fix

Confirm the code with an OBD-II scanner, then inspect the component or circuit named above. Consult a vehicle-specific service manual for the full diagnostic and repair procedure.