P0135 — O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
What it means
P0135 is an OBD-II diagnostic trouble code: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1).
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.