Code PO135, PO155

[Tunerguy1989]

I know these two codes are for O2 sensors I just need to know the location of the O2 sensors...Or can someone provide me a link to the a code thread..

[Towncivilian]

These codes are for both of the upstream O2 sensors heaters. Before replacing either, check the circuit. Instructions are on page EC-246 of the factory service manual.

[Tunerguy1989]

That was great help thx maN. so after diagnosing the problem I realized that All four O2 sensor connections are not getting any juice. So theRe seems to be a short some wHer between the harness and the ecu or the battery. Has Anyone else had this problem and could give me a starting point. I really don't want to rip out the harness and folLow the wiring to fiNd the short.
Damn electrical problems r the worst. All other connectors are fine so this seems so weird to. Its hard to believe corrosion would only affect the O2 wiRing.

The pathy has 190000 miles runS strong no other problems or leaks. I need to sMog it so this is a problem.

[Towncivilian]

Check the 15A fuse labeled "ENG CONT" behind the driver coin tray.

[Tunerguy1989]

I found the burnt out fuse, tHx for the help u saved me alot Of grief. But now I have a p0420 and p0430. Codes saying my catalytic converters are shot, Is that the only eXplanation for those codes?? I'm thinking the car was running rich for a while and it burned them out.

[Towncivilian]

Glad it was just a fuse.

Yeah, your cats are most likely shot. If your Pathfinder burns or has burned a lot of oil that really degrades the health and life of the cats. Running rich and/or cylinder misfire also dumps unburnt fuel into the cats which isn't good either.

Check for air intake leaks by spraying starting fluid or brake cleaner around the intake plumbing and vacuum lines; if engine RPMs raise momentarily, you found a leak.

Run some Chevron Techron fuel system cleaner (use the bigger 20oz bottles) in a couple tanks of gas back-to-back.

How many miles do you have on your Pathfinder? If you have 105k miles or more, were the spark plugs replaced with NGK PLFRA-11 plugs around this time?

[Tunerguy1989]

I did a full tune up around 160,000 miles, premium Iriduim plugs, cleaned K&N filter, and fuel filter was done around 120,000. It currently has 190,000miles. Why should I look for a leak? could an intake leak cause the catalyic converter code? I may try the Injector cleaner but I feel like that won't really do anything since I have read about injector testing with those cleaners and the difference made was very insignificant if any change at all.

But if it is the converters there are only two correct? someone told me there were four at one point but I thought they were full of it. I just want to verify, I think the guy was getting the resonators confused with the cats.

Damn Im looking at 400 dollars for both huh............. Sh#@ fml

[Towncivilian]

There are two cats on this vehicle.

Techron contains polyether amines, a chemical that has been proven to clean effectively without leaving behind its own deposits. It's nothing like that useless Lucas injector cleaner snot or the like. It's relatively inexpensive, give it a try. I would change your fuel filter after running two back-to-back tanks containing 20oz bottles of Techron, as the fuel filter has 60k miles on it and it'd be wise to change it out at that mileage in my opinion.

Intake air leaks are listed as a potential cause for your codes, so rule them out.

What specific spark plugs did you use?

[Tunerguy1989]

NGK platinums,the best ones they sell. I have my smog Extension for Another tWo weeks, I'll check the intake for leaks then give the techron a shot. I'll let u know how it goes. Fuel filter is easy I do thaT after as well.

Thx again man u've been a great help