intra

I have a 2004 350z that I just picked up a couple months ago. It seems to have issues starting when the front right o2 sensor is plugged in

Without this sensor plugged in the car works perfectly normal. When the sensor is plugged in the car will start, but will not idle. There is no input to the RPM meter, it will not allow input from the gas pedal, and after it shuts off it takes about 3 to 5 seconds for the car to receive power from the battery. After the car has stalled the airbag light, seatbelt light, and battery light all stay on for over 1 minute after the key has been removed.

So far I have tried replacing the sensor with aftermarket parts as well as a brand new OEM part. There are no kinks or tears in the wire and no other indications of bad wiring. There is a Stillen Cat-back exhaust system installed as well. Only the right front sensor causes this issue as when all the sensors are unplugged it runs fine, but when all sensors except this front right one are unplugged it won't idle.

It is also worth noting that I had to tear out wires from an audio system the previous owner had installed. The radio did not work and there were extra wires everywhere that were hanging loose in the trunk. Before these were taken out the car had the same issues except instead of stalling it would turn over but wouldn't start with the sensor plugged in. It seems every time wires are removed or grounded the car gets closer and closer to starting.

Could this possibly be a bad CPU or more likely a short somewhere in the system?

Chihuahuamaster

Are you talking about the upstream o2 sensor, located on the header? You definitely want these working, otherwise your AFR's will be off, and could be what's causing the idle issue. Yet when the sensors are unplugged, the car may go into 'limp mode' and still be able to idle, is there an RPM limit when you have them unplugged?

You can try to reset the computer and plug all of the sensors in, and see if there is a change. (Unplug battery for an hour or so).

It does sound like an electrical issue, (maybe a lack of ground), perhaps the sensor is not receiving the correct voltage.

You should be able to read the voltage output of the o2 sensors by using one of those OBDII scanners, and a phone app like 'Torque.' It may be different on older year models, but on an 2008, I am able to see the o2 sensor voltage readings, using this method. As for what they should output to see if they are correctly functioning, I know there is a thread on here giving that info.
I'm not the best with electrical stuff, but maybe this will give you some ideas if you haven't already tried these methods.

intra

Sorry, I should've clarified, its the downstream sensor on the right side. The car operates without any issues at all with it unplugged, no RPM issues, no extra lights on or anything. It only seems to occur when this sensor is connected.

Thank you for the suggestions!