Possible causes

– Faulty Air/Fuel Ratio Sensor Bank 1 Sensor 1
– Air/Fuel Ratio Sensor Bank 1 Sensor 1 harness is open or shorted
– Air/Fuel Ratio Sensor Bank 1 Sensor 1 circuit poor electrical conection

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1133 TOYOTA Description

The Air-Fuel ratio (A/F) sensor varies its output voltage in proportion to the air-fuel ratio. Based on the output voltage, the Engine Control Module (ECM) determines if the air-fuel ratio is RICH or LEAN and adjusts the stoichiometric air-fuel ratio. The ECM also checks the fuel injection volume compensation value to check if the A/F sensor is deteriorating or not. A/F sensor response deterioration is determined by the ratio of the A/F sensor output voltage variation and fuel trim variation.

TOYOTA Technical Service Bulletins for P1133 code