Heated oxygen sensor bank2 sensor1 heated oxygen sensor bank2 sensor 1 pending
SOURCE: E-Check Light P0125 and
Air/Fuel Sensors are mounted upstream of the catalytic converter. They are located on the exhaust manifold side of the catalytic converter (pre-converter - Sensors 1). Oxygen Sensors are mounted downstream of the catalytic converter (post-converter - Sensors 2). The catalytic converter has two chambers (left and right). Bank1 is left, drivers side. Bank2 is right, passengers side. The Bank2 Sensor1 sensor (Air/Fuel Sensor) is the one located on the 'right and ahead' of the converter. The PowerTrain Control Module (PCM) is reporting that the heater or circuit ( wiring / plug-in) of the sensor is malfunctioning.
SOURCE: HI I have toyota avensis verso
Air/Fuel Sensor Heater Circuit. (Bank 1 Sensor 2)
The A/F sensors are positioned high in the manifold before the cat and are used to make adjustments to the air/fuel ratio of the fuel injection system. The heated oxygen sensors are positioned after the cat and check the efficiency of the cat (what happened in there as a result of the A/F sensors above). They too can signal changes to the air/fuel ratio. These latter sensors only work when they are hot and need to be electrically heated quickly to give decent information quickly. They work by comparing the oxygen inside the exhaust with the oxygen on the outside.
You could say that the ones before the cat make large adjustments and the ones after make smaller refinements.
It is worth remembering that a fault code could have been stored because at some stage the sensor went outside of its range and for this reason it is always worth cancelling any stored codes as this sometimes puts the light out. There are also several other reasons why a sensor could be showing a fault (it is correctly saying that something else is causing incorrect air/fuel ratio) such as leaky EGR valves or vacuum pipes so just have a look around to see if there is anything obvious.
The DTC code will normally indicate the exact sensor that is faulty or at least showing out of range and not the group of sensors. In this case as you stand looking at the engine from in front of the car it is the top one on the drivers side.
Keep in mind they are sensitive devices (read that as fickle) and although you should start there you can often end up changing more than one and some cases even the cat before you can get them to settle down.
Good luck.
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