What do this code mean p1133 and how to fix it.?

P1133 = HO2 sensor 1 insufficient switching.

Possible causes,

An exhaust leak close to the O2 sensor,

Silicone gasket material contaminated O2 sensor,

Silicone in the fuel,

Leaded fuel added to the fuel tank,

Damaged wiring,

Engine oil consumption,

Engine coolant consumption,

Faulty O2 sensor.