O2 sensor problems

My guess is the gas your using is damaging the sensor's

What exact code are you getting (with the check engine light)?

I suspect you might be replacing the wrong O2 sensor.

Nirav

The code I'm getting is P0420. I'm pretty sure the O2 sensor that has been used is the correct one. I went to the dealer and gave them the VIN. That's when they informed me that my car was california emmisions. When I bought this car used the dealer(not a nissan dealer) had informed me that he'd just replaced the O2 sensor himself. A week after I bought the car they check engine light came on again. I took it back to where I bought it and he replaced the sensor again. Later the light came on again. I had since moved away and cash was low after taking the car to Autozone and finding out it was the O2 sensor again, I waited. Just about a year later that sensor got replace. This time I went directly to the dealer and got the part as I mentioned before. I've been reading around this group and noticed some folks that had to get their software updated in the 2000 models. Perhaps this is my problem?

That's a converter efficiency error. It often means it's time for a new converter. How many miles on it?

From the FSM:

DTC P0420 (RIGHT BANK, -B1), P0430 (LEFT BANK, -B2) THREE WAY CATALYST FUNCTION FOR CALIFORNIA

On Board Diagnosis Logic NFEC0214 The ECM monitors the switching frequency ratio of front and rear heated oxygen sensors. A warm-up three way catalyst with high oxygen storage capacity will indicate a low switching frequency of rear heated oxygen sensor. As oxygen storage capacity decreases, the rear heated oxygen sensor switching frequency will increase. When the frequency ratio of front and rear heated oxygen sensors approaches a specified limit value, the warm-up three way catalyst malfunction is diagnosed. Malfunction is detected when warm-up three way catalyst does not operate properly, warm-up three way catalyst does not have enough oxygen storage capacity. Possible Cause NFEC0504 I Warm-up three way catalyst I Exhaust tube I Intake air leaks I Injectors I Injector leaks I Spark plug I Improper ignition timing

It's over 100,000. If I remember right it's around 109,000. Unfortunatly the cat's were all replaced over this summer. That was a costly procedure that I never want to go through again.

What kind of cats were used? Some of the aftermarket ones can cause this problem.. As someone else said, sometimes the kind of gas being used can trigger this, does it use any oil?

The cat's were OEM but this problem first came up before the cat's went bad. I had a coil go bad and it took the mechanic longer then I would have hoped to fix it. By the time it was fixed, the cat's were blown. But like I said this O2 sensor problem came up before the blow cat. As far as gas, I guess that could be a problem. I just use regular. But no it doesn't eat up oil at all. Get's changed every 3000 on the dot. I figure with all the problems I have with the thing, the least I can do is change the oil on time. Sorry to be a broken record but is it not the ecu firmware? I know there have been a few threads in here about folks getting the p0420 code and having to switch out the firmware because of it being to "sensitive". Thank you all for your help so far. I really do appreciate it.

I had the same p0420 on my 2k cali SE with 104k and one dealer said to replace the cat, already had the new coils put in around 74k well i went for a 2nd opinion. Replaced the MAF (car however ran with a low idle/stalling) and had ECU flashed. Ever have the MAF upgraded to the new part number? That needs the reflash. Dont know if it does anything for the rear o2s. Running regular maybe a problem too, at least run mid grade!

I bought the car at 87k. At around 90k had to change all the coils due to severe engine shaking. Unfortunetly I let that problem go on for too long and ended up blowing out the cats. Got those replace around 95k. I've never replaced the MAF, but that's not saying someone else didn't. Is there a way for me a check that? If I do have the ecu flashed, is the dealer the only one that can do that? Ohh and I'll be sure to upgrade to mid-grade from now on!

What I've seen is you can get a false "bad rear O2 sensor" if the cat isn't doing it's job. These computers aren't perfect!

Yep, that's a bad idea on these cars. It causes the timing to be retarded ALL the time which makes the cats run much hotter than normal. WHile they say "It's OK" it's not good for the car. Also seen problems with certain brands (cheap?) like QT etc causing weird problems like this. Clear the codes and switch to a quality mid grade and see what happens..

nothing wrong with the sensor,,you need the software updated, and it should be covered under the emmissions warrantee,,,

M>The code I'm getting is P0420.

Just general gritching here - I had an 84 Max wagon - console fell apart & I passed it on the my kids to learn to drive on. Then we sold it to their friend several years ago. It's still wandering around the country just fine. Daughter 1 then got an 84 Max sedan. She drove it to 260k with no major problems. But we thought she needed something better for, say, D.C. Got her a 99 Max. She started driving it a few months ago. Check engine light has been on ever since. Just yesterday she found out her gas mileage has dropped to 18 from a consistent 32. We can't get it in to be tested until Dec. 12. Daughter 2 acquired a 91 Accord, drove it to 260 k. We upgraded her to a 98 Max. w/ about the same 80 k on the engine. Her Accord looks great, but mechanically it's dead. The 84 Max looks like death warmed over, but ran w/o a hitch, hence the interest in Maximas. D-2 just had NAPA replace an O2 sensor in Cal. to the tune of $260, and a week later the check engine light came back on.

kids into 57 Fords, and teach them how to change distributors and rebuild carburetors, and get the one kid out of LA! Good grief - are these things going to give them nothing but grief? Is the company really owned by the French these days?