P1172 Toyota Rear A/F Sensor Bank 1 Sensor 1 Circuit Out Of Range High

P1172 Toyota Rear A/F Sensor Bank 1 Sensor 1 Circuit Out Of Range High

Possible causes
– Faulty Air/Fuel Ratio Bank 1 Sensor 1
– Air/Fuel Ratio Bank 1 Sensor 1 harness is open or shorted
– Air/Fuel Ratio Bank 1 Sensor 1 circuit poor electrical connection
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
P1172 Toyota Description

The Air/Fuel Ratio (A/F) sensor 1 is installed in the exhaust system and detects oxygen content in the exhaust gas. The A/F sensor transmits output voltage to the Engine Control Module (ECM). A heater for the sensor element is embedded in the A/F sensor (sensor 1). It is activated and heats the sensor to stabilize and speed the detection of oxygen content by controlling current flowing through the heater. An increase in the current levels off as the applied voltage to the element electrode reaches a certain range because the amount of oxygen which is led through the diffusion layer is limited. The current amperage is proportional to oxygen content in the exhaust gas, so the air/fuel ratio is detected by the measurement of the current amperage. The ECM compares a set target air/fuel ratio with the detected air/fuel ratio and controls the fuel injection timing.

If the A/F sensor (sensor 1) voltage is low, the air/fuel ratio is lean, and the ECM uses A/F feedback control to issue a Rich command. If the A/F sensor (sensor 1) voltage is high, the air/fuel ratio is rich, and the ECM uses A/F feedback control to issue a Lean command.

Toyota Vehicle:Toyota Prius,Toyota Celica,Toyota Supra,Toyota Carina,Toyota Camry,Toyota MR2,Toyota Aygo,Toyota 4Runner,Toyota Avalon,Toyota Camry,Toyota Corolla,Toyota FJ Cruiser,Toyota Highlander,Toyota Land Cruiser,Toyota Matrix,Toyota Prius,Toyota RAV4,Toyota Sequoia,Toyota Sienna,Toyota Solara,Toyota Tacoma,Toyota Tundra,Toyota Yaris,
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