how to test or diagnose o2 sensor before replacing stuff

[mvmcali]

Hi All
my 2001 Qx4 has just passed 125k miles. im now getting the p0420 and p0430 codes.

before i replace the cat convertors, is there an (easy?) way for me to check the actual o2 sensors before and after the cat to make sure they are working right ?

i see these $20 wifi adaptors for the obd2 port and also $10 software for iphone. can i actually use these cheapy things to see waveforms coming off those sensors or is that something only pro/expensive tools do?

thanks!

[atraudes]

rgk did a damn good run-down of what he did to test his O2 sensor. I think it's still an open issue for him, but he had some pretty good ideas.

I had the same codes when I bought mine, though, and they went away promptly after replacing the cats.

Let us know how it goes!

[rgk]

There's unfortunately no mistaking it: P0420 and P0430 are most certainly catalyst codes. Your vehicle is at that ripe old age when replacement becomes necessary. Although they might only be 10% below efficiency, having that CEL light on constantly is a safety issue.

I drove my Protege around for three years with a P0420 before I finally replaced the cat with a high-quality aftermarket part (about $250). The light has been off for nearly a year.

Keep in mind that a rich condition can be cause for fouling of the catalyst, so if you suspect you have this, take care of it before replacing the cat.

However, if you really want to check your sensors, a good place to start is the FSM. It has step-by-step troubleshooting directions without the use of a code tool.

In my case, I have a $120 code tool. It can't graph, but it can give me real-time and freeze-frame data, which can be very helpful.

[mvmcali]

thanks both for your respnoses..

regarding code tools.. it seems there are these small $20 obd2 wifi devices as well as $10 smart phone apps. do you know if these things can more or less give you the same info that the $100+ traditional tools do?

i shutter to think what its gonna cost to replace the 2 cat convertors. a while back i helped my GF sell her older toyota corolla. the car was worth $4500 and a local garage wanted $3k to replace the bad Cat! i ended up goign to a garage where no english was spoken and they did it for $300 but i think i got lucky!

[atraudes]

The cats are only $150-200 each, and I paid a garage I think $300 to swap them in, so $700 altogether. I would've done it myself, but I don't even know how one gets to the bolts attaching them to the headers.

I got Walkers, but I've heard good things about Bosal and you can get Magnaflows too.

[cr4west]

I am using a cheap OBD2 reader ($8 - ebay) that creates a bluetooth connection to my android phone. The app that I am using is called torque. It has a real time graph function that is setup to monitor the output of each O2 sensor as you drive. In addition it has the capability to read and clear fault codes as I try different solutions. It was instrumental in successfully dealing with the P1440 and other codes with EVAP and the charcoal canister. Did it all by myself but took my time using the infinity shop manual and eliminating problems one at a time. Saved a ton of money. (1999 QX4 with 200k miles and going strong)

[mvmcali]

thanks for the reply. yep. i heard of torque. unfortunately i just switched to iphone so i think i have to use a different app . btw - at about 80k miles i did my own replacement of the downstream o2 sensors. now at 125k it appears that my cat's need replacement... did you ever replace your cat convertors ? what other repairs have been done on your way to 200k? i hope mine lasts that long.. i love this car!

[cr4west]

At 200k I am still running all original cats and all 4 o2 sensors and just passed a smog check. Other repairs were front rotors, 5 sets of auto zone ceramic life time guarantee brake pads, front hub bearings and outer CV boots, steering rack, mounting bushings and steering pump, front lower ball joints, front and rear struts, alternator pto bearing, internal regulator and set of 50A diodes, transmission oil, pan gasket and filter (done at 75k and again at 180k), 3 sets of tires, valve cover gaskets, tail gate struts, tailgate hinge, many light bulbs, tie rod ends, evap charcoal canister, AC compressor clutch bearing. front engine crank shaft oil seal (done at 75k and again at 180k), All the repairs I did myself thanks to this site. Cost was parts alone.

[cr4west]

oh and timing belt, serpentine belt and water pump too.

[mvmcali]

thanks for the reply...
all that and you never had to replace your Antenna Motor !?
hmm. I have about 130k miles on QX4 and havent had to do most of what you mentioned yet.
I did have to replace oil cooler gasket... which was tricky in that one garage was fooled by the leak dripping onto the front diff and they wanted to rebuild that. 2nd garage correctly saw the problem and saved me lots of $
-do you burn much oil? mine is still fine
-did you have the drivers side electric seat problem? I do (the seat is stuck but havent fixed it yet.

[cr4west]

Still using the original antenna motor but have replaced the antenna telescoping mast with the plastic toothed track/whip three times now by getting the kit off ebay (parking under low trees trashes the antenna). Engine does not burn any oil. Driver's seat still works. I recall something about a gear in the seat drive assembly that sometimes goes wrong. The driver's seat fix is mentioned elsewhere in the forum, try:
post6344282.html?hilit=qx4%20driver%20seat#p6344282
post6636505.html?hilit=qx4%20driver%20seat#p6636505
post6344282.html?hilit=qx4%20driver%20seat#p6344282

[mvmcali]

thanks. I will check out the fix for Drivers seat. Ive just been ignoring it for now .. but reminded of the problem when i let someone shorter drive the car.

i had the ant mast break only once but there was a piece of it stuck in the motor assembly. I had to take the wheel off, then the wheel well cover and then strugged with the motor assembly. had to take the whole damn thing apart and after getting it back together i found a large retaining spring had fallen out earlier! ohwell.. it seems to work fine.

how about fit/finish? my paint job is holding up great but the 'pin striping tape' along the fender flares has faded and cracked and the black paint on the roof rack is also deteriorating.

I also notice my headlight covers are all foggy. have you replaced or polished them and if so did it make a big difference?