l know that some older cars do not have o2 sensors past the headers. l was wonderinf if anyone knew if the 300zx is have o2 sensors around the catalyc converters, and if so are they before or after the cats. This information would be great

Before the cats.on the exhaust manifolds, they are quite well hidden!!! You can access through the front wheel wells behind the tires, there is an access area.

One on each side between the battery & rear cyl head passengers side careful around the A/C hoses with the wire on the side of the intake & inside of the brake booster left side with the three wire plug on top middle of the motor. Preaty much a straight shot with a O2 socket & 1/2 wrench & 14'' extension easier with the hood taked off. Passengers side u might want to play it safe & disconnect the battery. l toched the battery & the ac hose with my extension & wrench once & caused a A/C hose leak

There r 2. One is just to the right of the battery. Its easy to see & easy to reach if u take battery out. The other is under the brake booster. This one is hard to reach with out extentions on ur socket. Use the o2 senson removing tool (9.00 parts store). Only thing u make have to worry about is the last person did not us any anti-seize gel. This will call the nut that screws into the exausht header to come out with the sensor. They r a pain in the butt to get off the sensor. You may want to buy two at ur local nissan dealer just incase. Only other thing is weaving the harshness of the sensor around. Should only take about an hour to hour & half with proper tools.