QuestionQUESTION: Hi Calvin, you gave me some advise on Feb.6th - Subject '02 Nissan Xterra SE S/C - Engine Service Soon lamp blinking. You advised me that it can possibly be my oxygen sensor and to take it someone with a diagnostic connector which I did. The tech wrote a code PO430 and on this same comment/report indicated; "CAT Malfunction Bank 2." "O2 move together most of the time." "105K plus + T-BOLT DUE." According to the tech/service manager, oxygen sensor is OK. The tech reset my "engine service soon" and is no longer on, but told me it will likely come back on in a few days... My warranty is 8 years / 80K miles and I currently have 83.5K miles so my dealer is telling me that my warranty has expired and if it's the catalytic converter replacement(dealership still has to diagnose this problem themselves if they perform any work or estimate). Does this sound like my only choice is to replace the catalytic converter? And my estimate is quoted around $1,000. from the tech who gave me the dianostiic and the dealership is roughly estimating $1,500. Could there also be other hidden/possible problems which I may have to expect? $1000-1500 was well beyond my expectation/budget for this problem... Always appreciate your advice. Mahalo, Terence
ANSWER: Hi Terence -
Yes, I remember you.
What I would do is read the fine print of the warranty and see if certain items are on an extended coverage. Sometimes they are.
Secondly, I would not take any action until the light returns, if it does, in fact return.
In my opinion, the cat converter is not a show stopper and the vehicle can run great, even with it not working properly. There are 2 O2 sensors, one before the cat, and one after. If the O2 sensor after the cat is picking up too much emissions (as compared to the first sensor), this means that the cat no longer has the ability to remove CO, and thus signals the EMC to turn on the engine light.
If you live in an area where the engine light has to be off to get registered, then you might have to replace it. Otherwise, I would just let it go. Perhaps you can find one for a better price on line, and install it yourself. It is not a hard process. You can probably get by with half that price, maybe less. I can walk you through it, but you have to get access to the tools.
Hope thie helps -
aloha
calvin
---------- FOLLOW-UP ----------
QUESTION: Hi Calvin, my '02 Xterra's engine service soon lamp came back on after the reset with 165 miles of driving... I checked my gas cap by taking it off and putting it back on, and drove all day with small trips and the lamp is still on.
So, I suppose I must rely on the first diagnosis which I explained previously ("P0430 cat malfunction bank 2, 02 move together most of the time, 105K plugs(?) + T-bolt due"... which I believe the tech wrote.) I live in Seattle, WA and I believe my emission test is due in May. My car is currently running fine with the engine light on; normal/smooth idling and ran fine today in city & freeway. I called Nissan helpline and they again told me my cat warranty is good til 80K miles or 8years, but of course they insist to take it to Nissan dealership to get it diagnosed to see if it's actually the cat w/problem since it can be possibly something else with a minor repair or something that can be covered under warranty(which I don't think nothing will be over 80K miles anyways..). I also was wondering about your previous comment/advice about the O2 sensors, but does my diagnostic result from the tech give any indications that my O2 sensors are OK? Especially if it's the sensors before the cat? Just wondering if it can be the faulty sensors before the cat and hoping my cat is OK...assuming this will be a less expensive repair too. Otherwise, if you feel the cat is the problem, I suppose I have no choice but to either try replacing the cat by some licensed mechanic or by myself. (again, the tech's estimate is $1000 for parts/labor repair and $1500 estimate by the dealership!) I'm hoping I'm doing the right thing/repair and do not want to find out later that it's something else other than an expensive cat, like my O2 sensors or bad spark plugs or ??? Or do you think it's still worth taking it to the dealership and paying again for another diagnostic test...with an high chance of getting similar and bad news on the expensive repair? Sorry with so many questions, but really appreciate your guidance. Mahalo, Terence
ANSWER: Hi Terence -
I wish you were here, I would do the diagnostic for free. It will also make things a lot easier if I had the car in front of me. It is very difficult to provide an accurate diagnosis "sitting on the bench".
With that said, my advice is to, as much as you can avoid the dealership as much as possible. I don't know if you have a reputable mechanic in your area, but it is important to find one that you trust, and will not take you for a ride.
I have one question. You mentioned that after 165 miles the light returned. Was that freeway driving, or city?
According to my chart, PO430 reads "catalyst system below threshold bank 2". This tells me that the second O2 sensor may be faulty, or the cat converter. I assume you have tuned up the car (at least replace spark plugs?), checked for vacuum leaks, etc.? Since it is running fine, maybe so.
Bottom line is, if it were my vehicle I would do anything that I can that I can do myself to correct the problem, i.e. replace plugs, O2 sensor, check wiring for the latter, etc.
Terence, I hope this helps.
aloha
calvin
---------- FOLLOW-UP ----------
QUESTION: Hi Calvin,I took it one mechanic that I can trust and gave me free diagnostic. The scan was the same PO430.
About your inquiry on my driving after 165miles when the light returned, it was combination of freeway and city driving(my use/commute is a split freeway & city driving). My commute one way is about 8-9 miles and the light came back on the 9th day w/165miles driving.
As far as tune up, my last work done was about 24Kmiles ago with dealership(60K miles service job, before my extended warranty expired) and it doesn't look like they changed my spark plugs at that time.
The first tech who gave me diagnostic also wrote no leaks on the exhaust so I'm assuming it's OK underneath. Although I may not detect it by myselft, I will also check under the hood for any possible vacuum leaks tonight. Another thing about my car is that long ago (60Kmiles ago), a car had hit my back corner which bent the exhaust tail pipe which the mechanic bent back w/crow bar, but possibly it's not fully straighten at the curve...however I believe it's not really causing bad exhaust flow.
Again, my car has been running fine. One small thing the tech mentioned, which I didn't think it was too important at the time & didn't listen in depth, was that my coolant (ph?)level had low figure I believe...which I told him my only risk is damaging my radiator which he nodded & didn't comment... Other than something out of the ordinary recently done to my car was that I topped off my oil with a quart of oil stabilizer on my last oil change.
Lastly what I can remember which sort of bothers me, was I had J-Lube give me Fuel System Cleaning Service about 10K miles ago. Immediately after the service was done, I remember I had a lot of white exhaust coming out of the tail pipe along with some rough idling. My normal idling came back within a half an hour of driving or so, but the more than usual smoke was coming out for the good part of the day. I'm thought this was normal at the time, but I hope this didn't aggravate or harm the cat/sensors by any chance...
I agree, as you mentioned, that I'm willing to do things myself to correct the problem... such as changing spark plugs, checking vacuum leaks. You mentioned about check wiring for the latter which I'm not familiar... and is there some other simple checks you can suggest which I can do by myself? Possibly by letting me know what you would do/check or "to do" priority step list? Just want to at least give it a try by myself before coming to a final verdict on a cat repair.
I hope I gave sufficient info for you to possibly analyze, I understand it's tough sitting on the bench there but I always appreciate your advice/suggestions... Mahalo, Terence
AnswerHi Terence -
First of all, just in case - this website cuts you off if the thread is continued too long, so if it does, my email is cjiwash@yahoo.com.
That fuel system cleaning service concerns me too. I would assume you cannot find out what exact product they used? Sometimes they may not be compatible with cats and oxy sensors.
What I meant by wiring is to check the runs for the oxy sensors, just in case they came into contact with the exhaust and somewhere lost connection to the EMC. Just a wild shot, but I say everything must be checked.
Yes, this is a tough one, and the last thing I want you to do is replace the cat converter and it is not it, however, from what you tell me, perhaps it will end up with replacement, as I am running out of suggestions.
Let me do some research.
thanks
calvin
