If tests show that a sensor is normal and cannot be causing any driveability problem, check wiring harness and connectors between that sensor and PCM for opens or shorts. : If none of the above is present the vehicle should be taken for an assessment by an A-grade facility. The exhaust mixes with the O2S and produces voltage output which will range 0.1V, which is a lean cylinder to 0.9V, which is a rich cylinder. The upstream O2S informs the PCM concerning the state of the oxygen in the exhaust for the best setting of the air/fuel mixture thats 14.7:1 to minimize emissions, fuel consumption, and achieve top performance. The downstream O2S appears similar to the upstream sensor it does not affect air/fuel ratio, but rather is employed for evaluating the functioning of the catalyst. O2S does not generate voltage until it ascends up to around 600 degree F, this period the PCM in turns runs with open-loop depending on other sensors. The flow of electricity should be accurately connected, the air supply should be unhampered in its quantity and access to correct operating temperature, and unleaded fuel is recommended. The EEC system of the O2S can monitor different problems and set the DTCs; when a fault is present, PCM will switch to the open-loop control. In checking, attach a voltmeter to the O2S connector; the reading should be positioned at about 400 to 450 mV with the ignition on. When the engine is warmed up the upstream sensor reading should be oscillating from 100 to 900mv and downstream should be steady at sometime in the same range. Also, perform a check on the battery voltage supply to the O2S heating circuits, specifically, with the ignition on, the amount should be over 10 volts. When removing an O2S, it is recommended to warm up the engine to make it easy for removal of the part; be careful not to damage the pigtail as well as the connector; prevent the accumulation of any contaminants; and do not use any cleaning solvents. When the vehicle is raised safely and secured, remove the electrical connector, use the right tool to remove the headset and if the compound is not pre-coated, apply the anti-seize on the threads, then fit in the new sensor, tighten it and fit back the electrical connector.