o2 sensor

[robdancarter]

It looks like my o2 sensor is bad on my 2001 Qx4. Is there a cheap and easy way to get this fixed? I'm thinking of just ordering the part and then taking it to a mechanic to get it replaced. Any tips or estimates on the cost of this? I know it is a common problem with the Qx4s.

[RR425]

Just changed the bank 2 sensor 2 (downstream drivers side) sensor on friday. Bought it online for $75 and changed it myself. Drove around for 30 miles and the check engine light came on. Does this mean the cat converter is bad??? I have to pass emissions by next month.

[Mark Sheriff]

@robdancarter, you can probably replace the sensor yourself, those are not hard at all

@RR425, it could be your cat thats blocked up, did you get the code for the check engine light you have?

[RR425]

Don't have the code on me (need to get a code reader) but shop said bank 2 sensor 2.

Has anybody here replaced cat converters on the QX4? Looked at it today and it looks super difficult. Can't even remove the heat shields around the cats. If I even manage to reach a bolt, it is super rusty. Looks like it will be a challenge.

Stupid question: if cats are blocked up, can they be cleaned out or do I need new ones? Never changed them before and don't know anything about them.

ps. The cats on my car seem to get really hot after even short driving. Car drives fine, but when stopped there's always this tin-tick-tin-tick noise hot metal makes as it cools. And now that I got under the car today it seems to be the cats. So they probably are blocked up.

[Mark Sheriff]

the sounds you hear are normal and its caused by the heat expanding and contracting the metals, if your cats however are getting extremely hot and if you look at it and its kind of red, then yeah you have some bad cats lol, the cats can be hallowed out i believe(gutting the cat of the honeycomb material inside it), this will be like you have no cat but the car will function normal and you shouldn't have any check engine light, in fact the car would probably run better

[RR425]

I hate Nissan right now. Such a pain in the *** trying to remove the heat shields from the catalytic converters on the QX4. Can't remove the cats without doing that. The screws on the heat shields won't even budge. I'm down to beating them with a chisel, but there are 4 that I can't even reach with a chisel or metal saw. Thanks a lot Nissan!

Would I pass emissions with hollow cats?

[Mark Sheriff]

you would pass emissions because they wouldn't know the cats are hollowed out lol, they will see the cat as present but they dont know whats going on inside it

try starting the car and making that cats real hot and therefore the bolts will be hot and maybe easier to come out

[RR425]

the sounds you hear are normal and its caused by the heat expanding and contracting the metals, if your cats however are getting extremely hot and if you look at it and its kind of red, then yeah you have some bad cats lol, the cats can be hallowed out i believe(gutting the cat of the honeycomb material inside it), this will be like you have no cat but the car will function normal and you shouldn't have any check engine light, in fact the car would probably run better

So really, no check engine light? Wouldn't the downstream o2 sensor be going crazy? I have to fix this to pass emissions. I don't think my cats are red, but my check engine light has been on because of the downstream sensor. Replaced it and it still came on 30 miles later. So I assume the cats are bad. I would happily hollow them out if the damn CEL would leave me alone.

Edit: ok just saw your previous post. Thanks for the info. Seems like a set of chisels and a metal saw does the trick as far as removing the heat shields. Got 2 so far 2 more to go.

For the hollow cats- I'm not worried about the emission poeple as much as the o2 sensor. And they won't let me pass emissions if the CEL is on.

Do you have hollow cats on your Pathfinder? Anybody done this on QX4?

[Mark Sheriff]

i haven't done this to my pathfinder but i would do it if my cats went bad, i have removed my resonators though and i have a flowmaster muffler on
it really cant hurt to hallow out the cat because either way if it doesn't work, you still need a new cat lol
i say hollow it out and screw it back up, screw your o2 sensor in it, then unplug the car battery and reset the ecu, then drive and see if the cel ever comes back on

[RR425]

I assume my cats are bad because I replaced the downstream o2 sensor and light still came on. If they are definitely bad then yes, I'll hollow them out, can't hurt

So exhaust is a known problem for these cars?

[atraudes]

I had to get the cats replaced on my 01 QX4 when I bought it. I spent an afternoon just trying to get the shields off (never mind the bolts to the headers) and gave up. I ended up having a shop do it. After seeing what they were up against, I'm still not sure how they did it!

I don't give up easy, but I'm still glad I did that time. Life's too short to bust my knuckles on that mess.

[QX4ME]

you can probably replace the sensor yourself, those are not hard at all

I looked underneath without lifting the car and didn't see where the O2 sensor is. Maybe I didn't go inward enough. Does Bank 2 Sensor 2 needs dealer reprogram (or rest)? I got confused that some sensor does others don't.

Code P0158 came on recently. I erased the code twice. It came back on in about 80 miles.

[Mark Sheriff]

yeah look around better, should be easy to spot, i don't think you have to have anything done like reprogramming the sensor at all, just swap out
i know when i look under my hood i can see my upper o2 sensors and when i go under the car i can see my o2 sensors right before the resonators, in my case i don't have resonators because i removed it so i see them before my straight/intermediate pipe.

[RR425]

I got the P0430 code. Looks like there might be a hole in the exhaust somewhere. Probably don't even need to replace the cats. Spent all weekend removing the heat shields for nothing

[QX4ME]

... i don't have resonators because i removed it so i see them before my straight/intermediate pipe.

What does resonator do? To tune the exhaust sound? Do you gain a bit power with resonator removed? Any sound change?

Thanks.

[attofarad]

I have a similar problem, P0430 after replacing a bad downstream sensor. Comes and goes. i.e., I can reset it and it may stay gone for weeks.

This code will appear when the upstream sensor is changing phase (rich-lean-rich-lean) slower than 1.33 times as fast as the downstream sensor. This can be because the cat is bad, so that the downstream sensor is switching too fast. I'm guessing that it can also be because an old upstream sensor has gotten slower to switch as it ages, even if the front sensor is not slow enough to trigger a P0133/P0153 code. Combined with a fresh downstream sensor, maybe the switching ratio creeps over the limit.

I bought a replacement front sensor 3 months back, but the code went away so I had not installed it. Last week, the P0430 came back. With 188k miles on the original front sensors, I should replace them anyway, to get better mileage and better gas catalytic converter life. Maybe weekend after next.

Manual says other things that can cause the P0430 code:

Possible Cause
Warm-up three way catalyst
Exhaust tube
Intake air leaks
Injectors
Injector leaks
Spark plug
Improper ignition timing

[RR425]

Just went to a shop today and they said 99% P0430 means cat converter. My car only has 120,000 miles and the check engine light has been on since I bought it with 98,000. It was an o2 sensor so I didn't pay it much attention.

Also, he said it could be a software update thing. My QX4 was built 6/00, so I probably need to go to a dealer to check for updates. As far as I can understand, my ECM Part Number should be 23710-4W000 or W001 or W002.

[Mark Sheriff]

... i don't have resonators because i removed it so i see them before my straight/intermediate pipe.

What does resonator do? To tune the exhaust sound? Do you gain a bit power with resonator removed? Any sound change?

Thanks.

resonators aid in keeping the cars exhaust quiet and can also help reduce the raspiness sound. i have removed the stock muffler, the muffler/silencer near the tailpipe and also my resonators, i have a flowmaster exhaust on there and that's it, luckily i have no raspiness after removing the resonators.

[RR425]

Do after market cats work fine? No codes? Can get those for $250 a piece.

[Mark Sheriff]

any cat that fits your vehicle correctly should work fine, also check to make sure the o2 sensor openings are in the right spot on the cats before buying, just to make sure everything will fit correctly

[RR425]

http://www.energeticforum.com/renewable ... ulers.html

Instead of replacing the cats, that is what I tried to do. It costs $15 and it works. The only problem- on the QX4 passenger side the transmission is in the way and the modified sensor will not fit.

[robdancarter]

So if my 02 sensor circuit high volts (bank 2 sensor 2) is bad, what part do i need to order? Admittedly i don't know much about cars. There is too much to choose from on Rock Auto.

[attofarad]

robdancarter:

One choice is to get the "universal" one, and cut your old cable and splice it to the new
sensor (splice comes with the universal sensor), so that you re-use the original connector
to the harness. Problem is, that it can be difficult to get a sufficient length of the old cable
out, because it is impossible to reach the anchor points. This is especially true for the
downstream/rear/sensor2 on the passenger side, but also difficult on the driver side.

I found it easier to just pay the extra dollars to get the one with the correct connector.
Be aware that the connector changed during the 2001 QX4 year, either a green connector
or a gray connector -- these are not interchangeable, will not fit. You need to look
at the connector yours has, and then go to the Bosch site at
http://www.boschautoparts.com/VehiclePa ... inder.aspx
enter your year/model, select oxygen sensors, etc. Eventually, you will find
"early" and "late" production choices. For the Universal one, it is the same part number,
since you would reuse the connector/cable. For the OE fit one, there are two
different parts. For instance, the downstream left side (I think that is bank2 sensor2,
but you need to verify)
http://www.boschautoparts.com/VehiclePa ... _num=13651
for late production, and
http://www.boschautoparts.com/VehiclePa ... _num=15445
for early production

RockAuto is one of the few parts sites I found with actual photos to show which connector.
They were also about the cheapest, and I ordered from them.

Gary

Edit: The rear/downstream sensors themselves are easy to get to from under the vehicle.
You can fish the connector/cable through with a fish tape or coat hanger or some such.
The fronts, which I'm planning to replace, seem very difficult to get a wrench on.
Anyone with advice (especially driver side front O2 sensor) of how to get at it?