Well, after my "Service Engine Soon" came on last night, I went to Autozone to get a free scanning. PO134(Oxygen Sensor) and PO328(Knock Sensor) came up. I thought the knock sensor didn't throw a code? Fucking lieing Nissan scumbags! Anyone know what might cause the O2 to have a problem? It's okay to drive, right? I'm calling Nissan Headquarters before I go to any dealership, since I've had problems due to my "heavily modified" Xterra (eyeroll) Any tips on how to deal with dealerships that might give me trouble about doing the work since I have soem mods on my truck? Thnaks in advance!

The knock sensor throws a code, it doesn't, however, trip the check engine light.

It's certainly ok to drive it, but your mileage may suffer.

I have had the O2 sensor code many times. Usually what I do is clear it and see if it comes back. O2 sensors are expensive and you have four of them. They can fail, but often it is an errant voltage that trips the code.

With my code reader, I can check the voltage values of the O2 sensors so when I get a code I clear it and then check the voltage values they are sending and check them against the ESM. If they are in spec, there are no worries.

A good code scanner can save you literally thousands in repair costs.

knock sensor does trigger a code but not MIL. I would erase the fault and see if it re-occurs. Sometimes O2 codes pop up and then never occur again. If the O2 code does present itself again you will want to do a resistance check on the sensor . The specs will be in the FSM (I lost my copy). If the sensor checks out you would want to check the wiring harness for the same readings at the ECU end to ensure there is continuity through the harness. If that checks out I would look for an exhaust leak before the sensors since something like a manifold crack that is leaking exhaust gases can give you a false reading at the O2 sensors sometimes depending on the location/size of leak. there are other things to check but these areas are where to start.


Do the sensor resistance check first, most likely your sensor just quit on you.

I have an extended warranty that expires at 75,000 miles/10/15/2008, will this cover them?

Perhaps...O2 sensors may be considered a wear item. You would have to check your warranty and what it says.

I remember reading about someone spraying their engine at the car wash then soon had problems with their O2 sensor. I had some mud caked to the engine and hood, two weekends ago I sprayed off the engine at the car wash (on low pressure) I have done this many times with my Toyota trucks. I'm going to go disconnect the battery now.

My junk used to throw these codes every time the inside of my engine compartment got wet. When I was still under warranty the dealer changed the wiring harness. Apparently the clips that sit on top of the engine can get water in them and cause a code to be thrown. Like Scott said
I now goop dielectric grease on all of those connections (thanks Scott) and if it still happens I clear the code, let it dry and all is well until the next time.

whew..i guess both the oxygen sensor and the knock sensor are causing your problems. Anyway, were you able to resolve these issues already?