Located just below the four into one point of the exhaust manifold on the engine block side.—-
The Oxygen Sensor contains two porous platinum electrodes that produce an electrical output proportional to the oxygen level exiting the engine. Because it only operates efficiently at high temperature, in order to speed up the warm up cycle, a heating element is integrated into the sensor.
The oxygen level in the exhaust gasses gives the ECU a good indication of the Air Fuel Ratio. The ECU will adjust the injection system in order to maintain the correct AFR. This process is relatively “dynamic”(100mS cycle time) with the ECU continually re-adjusting, this can be seen by the swing in the Lambda output signal prior to blipping the throttle here . When cruising at a steady speed (not that often in a 7) the ECU will go into a closed loop mode using the Lambda sensor output to run the engine as lean as possible.