oxygen sensors on 1990 Nissan 300ZX

Does the oxygen sensor directly measure the amount of oxygen in the exhaust gases or is it a thermocouple type device that measeures exhaust gas tempatures and this information is then used to determine the amount of oxygen in the exhaust gases? Is there a way to test a oxygen sensor out of the vehicle with a VOA meter or other device to determine that it is working? How many oxygen sensors are on a 1986 Nissan 300zx? Is the sensor or sensors located in the exhaust manifold or elsewhere? Thanks, awaiting a reply.

by in Marina del Rey, CA on February 27, 2009
1 answer
ANSWER by , February 27, 2009
The O2 sensors in your car measure oxygen left in the exhaust after combustion (they do not measure temperature). The O2 sensor generates a small voltage. The fuel injection computer uses this input to trim the on time of the fuel injector on time to keep the engine running at a desired air fuel ratio. The O2 sensor generates a low voltage when the fuel mixture is lean and a higher voltage when the mixture is rich. This is best tested using an oscilloscope to view the out put pattern. You can use a digital voltmeter to see what is happening. Driving the mixture rich the a voltage will be about .8v and driving the mixture lean the voltage generated should be .1v but it is the response time and speed of change of voltage you need to have experience looking at to judge if the pattern is good or bad. There is one sensor per exhaust bank on your engine. Our web site has an extensive article on emission control systems, and you can find removal procedure and locations at this site. http://www.autozone.com/N,9010961/initialAction,repairGuide/shopping/vehicleSelect4.htm