Faulty Air Fuel Ratio (A/F) 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 connection
Faulty Engine Control Module (ECM)
Engine Light ON (or Service Engine Soon Warning Light)
The Air Fuel Ratio (A/F) sensor generates a voltage that corresponds to the actual air-fuel ratio. This sensor voltage is used to provide the Engine Control Module (ECM) with feedback so that it can control the air-fuel ratio. The ECM determines the deviation from the stoichiometric air-fuel ratio level and regulates the fuel injection duration. If the air-fuel ratio sensor malfunctions, the ECM is unable to control the air-fuel ratio accurately.
The air-fuel ratio sensor is a planar type and is integrated with the heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are narrow types. The heat generated by the heater is conducted to the solid electrolyte through the alumina, and therefore sensor activation is accelerated.
In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) components in the exhaust gas, a three-way catalytic converter is used. For the most efficient use of the three-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric level.
The Diagnostic Trouble Code (DTC) is set when there is an open or short in the air-fuel ratio sensor circuit, or if the air-fuel ratio sensor output drops. To detect these problems, the voltage of the air-fuel ratio sensor is monitored when turning the ignition switch to ON, and the admittance (admittance is an electrical term that indicates the ease of flow of current) is checked while driving. If the voltage of the air-fuel ratio sensor is between 0.6 V and 4.5 V, it is considered normal. If the voltage is out of the specified range, or the admittance is less than the standard value, the ECM determines that there is a malfunction in the air-fuel ratio sensor. If the same malfunction is detected in the next driving cycle, the MIL is illuminated, and a DTC is stored.