P0420 - Nissan Maxima 2000

[brushandcr]

Hi,

After spending a few bucks for a reader/code clearer, it turns out I received what seems to be a dreaded P0420 code. I cleared the code about a week ago, but came back yesterday.

I had the MAF sensor replaced due to roughness on start up, and since the MAF was replaced (shop advised I get Nissan MAF as it was only $8 extra) and reprogrammed the start up and ride has been perfectly fine - so the problem was corrected.

I did a bit of research and found a TSB from 6/2004 (007A) related to this code/reprogram. I contacted a local Nissan dealer/service center and asked what they suggest I do and whether there would be any cost to reprogram. They responded back saying they would suggest a reprogram before replacing anything related to the catalytic converter and would be $110.

Note: I have 74K miles and I believe the catalytic converter itself is warrantied until 80K miles (im in New Jersey if it makes a difference).

Questions:
- Can you confirm that there there truly should be a cost for code coming up possibly due to issue represented by a TSB? The local Nissan service center manager says its $110. I would obviously bring this up with the local shop that did the reprogram, but not sure they can handle per second question.
- The local shop did perform a reprogram; would there reprogram include this TSB fix or will it only be included in the dealer reprogram?
- Ive read this code may not be the catalytic converter itself but a related part not covered under warranty. If it is determined that the programming is fine, would the dealer service center charge to determine the cause or just replace the catalytic converter as I got in writing? I believe normally for them to just look at it for a few minutes is $110.

Thanks for any help.

[MTZI30]

Heres a few answers: If your car is a 2000, its more then 8 years old so it wont qualify for any emissions warranty.

Yes, there is going to be a cost for a tsb related issue. Recalls dont cost anything, Tsbs are different. If the car was under warranty there wouldnt be a cost.

They can try a reprogram but it sounds like you need a catalytic converter, it is a known issue on these cars. An 02 MAY cause a similar code but then you should have 02 codes.

I had the same code you did, however this happened when my car was still within the 8 years of the delivery date and luky me, at 78k miles so I was covered. From what you wrote, I cant see your car covered by any warranty. Like i said sounds like you need a new cat. A car at that age is going to be 100% customer pay.

No offense but your post is kind of hard to understand....hopefully this was helpful.

[the converted]

That reprogram is because they started using different MAFS for those cars, and there is no way that the shop could have reprogrammed it. I don't think that the two are related, but it is always a possibility. If you are looking for the cheap way out, you can either put an o2 simulator in the car, or you can try using spark plug anti-foulers on the o2 sensor.

[loystock]

PO420 points to Bank 1 Pre-cat problem and/or related Front and Rear O2 sensors. It could also be caused by intake/exhaust leak or misfire. Since your car idles smoothly and as long as you don't have acceleration issue, then we can eliminate the leak or misfire as cause.

Your car has 3 catalytic converters - Bank 1 Pre-cat, Bank 2 Pre-cat and Main cat. Bank 1 (cylinders 1-3-5) is towards to firewall while Bank 2 (cylinders 2-4-6) is towards the radiator. We'll focus on Bank 1 since that's where the problem is. Bank 1 Pre-cat is mounted horizontally, under the engine. In front of Bank 1 Pre-cat is the Rear O2 sensor. The Bank 1 Front O2 sensor is mounted on the vertical portion of the exhaust pipe.

How long was the engine running rough before the MAF sensor was replaced? A rich fuel-air mixture can cause the O2 sensors and cats to fail prematurely. OEM cat is expensive, cheaper with aftermarket cat but questionable quality and durability due to lower level of Platinum-Palladium-Rhodium inside. OEM Bosch O2 sensors are also expensive, @ $150 each, but NGK/NTK sensors can be had for $50-90 each.

Only the dealership can re-program the ECU to address this particualr issue. You car is past the Federal Emission warranty, 8-yr/80Kmiles, unless NJ has a longer warranty. If I were, I'd have the ECU re-programmed. If it didn't fix the problem, then replace both Bank 1 O2 sensors. I will only replace the Pre-cat as a last resort.

There is no harm is checking the intake and exhaust for obvious signs of leak. Check the air filter too and replace if dirty.

[brushandcr]

I had thought the warranty was 8 years OR 80K miles and since I was at 74K miles it would be covered. If not, this likely isn't a good situation unless it turns out to be the reprogramming.

The start up was semi-rough for a month or so (it wasn't bad and went away after 20 seconds) and finally came up with a code that showed LEAN on both banks. I brought the car in and the local shop cleaned the throttle body and did not resolve so the next day they replaced the MAF. That night when I picked it up it was much better - no roughness at all and had no issues for ~2 months until the light came on. I got the code and cleared it to make sure it wasn't a fluke and a couple of days later came back on.

Q's:
In regards to the reprogramming, the local shop did do this (and was charged as such - $60); are you all saying this reprogramming is not the same or worthless compared to what the dealer would do?

The warranty is definitely over if at 74K miles (10 years old)?

I can do some basic work on the car, but wont be able to do any of the O2 sensors, pre-cat, etc. What is the general cost for the pre-cat replacement, 02 replacement for parts/man hours?

With the car the way it currently is, am I doing more and more damage each trip to work and should have this examined asap? I will try and schedule the reprogramming as soon as I can, but if that is performed and it does not fix the problem, am I killing the car by continuing the drive 50 miles a day on it?

Thanks.

[loystock]

I had thought the warranty was 8 years OR 80K miles and since I was at 74K miles it would be covered. If not, this likely isn't a good situation unless it turns out to be the reprogramming.

The start up was semi-rough for a month or so (it wasn't bad and went away after 20 seconds) and finally came up with a code that showed LEAN on both banks. I brought the car in and the local shop cleaned the throttle body and did not resolve so the next day they replaced the MAF. That night when I picked it up it was much better - no roughness at all and had no issues for ~2 months until the light came on. I got the code and cleared it to make sure it wasn't a fluke and a couple of days later came back on.

Q's:
In regards to the reprogramming, the local shop did do this (and was charged as such - $60); are you all saying this reprogramming is not the same or worthless compared to what the dealer would do?
-the programming was to allow the ECU learn about the new MAF sensor. It's not mandatory as the ECU can learn the new MAF sensor over time.

The warranty is definitely over if at 74K miles (10 years old)?
-Warranty is based on whichever comes first, duration or mileage

I can do some basic work on the car, but wont be able to do any of the O2 sensors, pre-cat, etc. What is the general cost for the pre-cat replacement, 02 replacement for parts/man hours?
-do the re-programming first and then go from there. There are several choices forthe O2 sensors and cat.

With the car the way it currently is, am I doing more and more damage each trip to work and should have this examined asap? I will try and schedule the reprogramming as soon as I can, but if that is performed and it does not fix the problem, am I killing the car by continuing the drive 50 miles a day on it?
-hopefully, the problem is just due to misdiagnosing the P0420 problem which re-programming may fix.
Thanks.

[brushandcr]

I e-mailed one of the local dealers and am waiting for a response about an appointment to get the reprogramming. I also called Nissan Corporate and they gave me a case number and told me that the 8 year/80K mile warranty on emissions will not apply as my car is 10 years old.

Lo and behold, this morning when I started the car the SES light is now gone - which is good and bad I guess. Perhaps as you had mentioned, it could be learning that it is not truly a problem.

Q's:
- What would cause the SES to disappear? Is it as simple as a period of time lapses with the car on and without the error returning it will automatically shut it off?

- Back to the question on the programming, I perhaps didn't ask it correctly. If I reprogram at the local shop (mom and pop) compared to doing it as Nissan is there a difference (will Nissan have newer programing with all of the TSB fixes that the mom and pop will not have?)

Thanks in advance!

[the converted]

If it went away, the condition that caused it has been gone for about 50 miles of driving.

There is NO WAY that the mom and pop would have been able to reprogram unless they went to the Nissan dealer themselves. They would have had to have a consult which Nissan won't distribute to anyone except the dealers.

[MTZI30]

I had thought the warranty was 8 years OR 80K miles and since I was at 74K miles it would be covered. If not, this likely isn't a good situation unless it turns out to be the reprogramming.

The start up was semi-rough for a month or so (it wasn't bad and went away after 20 seconds) and finally came up with a code that showed LEAN on both banks. I brought the car in and the local shop cleaned the throttle body and did not resolve so the next day they replaced the MAF. That night when I picked it up it was much better - no roughness at all and had no issues for ~2 months until the light came on. I got the code and cleared it to make sure it wasn't a fluke and a couple of days later came back on.

Q's:
In regards to the reprogramming, the local shop did do this (and was charged as such - $60); are you all saying this reprogramming is not the same or worthless compared to what the dealer would do?

The warranty is definitely over if at 74K miles (10 years old)?

I can do some basic work on the car, but wont be able to do any of the O2 sensors, pre-cat, etc. What is the general cost for the pre-cat replacement, 02 replacement for parts/man hours?

With the car the way it currently is, am I doing more and more damage each trip to work and should have this examined asap? I will try and schedule the reprogramming as soon as I can, but if that is performed and it does not fix the problem, am I killing the car by continuing the drive 50 miles a day on it?

Thanks.

Some bullet points:

*Yes the warranty is 8 years or 80k miles. (Whatever happens first)

*You will prolly have to replace part of the catalyst. Dealership cost is going to be very high. One cat is prolly 1000.

*Now in the second paragraph be more detailed. Did that same lean code come back or did another code come up?

*The programming i cant imaging would be much different or different at all then what the dealership uses.

*Yes if the original delivery date of the car was before 1/4/03 its out of federal emissions warranty.

*Well depends on which cat you have to replace. Shops might charge anywhere from 1 hour to 4 hours of labor at anywhere from 80-150 dollars an hour. As for parts as i stated above one factory cat could go for 1000 if you buy at a dealership plus labor. I've used aftermarket cats and have never had a problem. As for the 02 sensors, an example, one guy asked for 2 hours with diag just for one 02 sensor, the part was 300. I got lucky since i work at a shop i got it in for one hour and bought an ngk plug from amazon.com for 70. (Thanks loystock) If you get some quotes look at how much time(labor) they're asking for and how much the part is. Also ask them where they get their times from, that dude wanted to charge two hours but the labor book only calls for one and IMO 1 hour for diag is too steep for me for a damn 02 sensor.

*I wouldnt worry about a bad catalyst. Just the 02 sensors are sayingto the computer its not doing its job of converting the exhaust gasses into less harmful materials so you have a cel (check engine light). Hope this helps....

[MTZI30]

If it went away, the condition that caused it has been gone for about 50 miles of driving.

There is NO WAY that the mom and pop would have been able to reprogram unless they went to the Nissan dealer themselves. They would have had to have a consult which Nissan won't distribute to anyone except the dealers.

Thats a good point. I remember at my old autoshop we had some generic cards that would get into our scan tool and had some generic software for most brands.

[brushandcr]

*Now in the second paragraph be more detailed. Did that same lean code come back or did another code come up?

I forgot the code that I received prior to the MAF installation - it was a code for running lean on bank 1 and 2 (or both banks if not called 1 and 2). After the MAF installation it came up with a P0420. Perhaps I can look back at the mom & pop shop invoice and it may have the code(s). If I find it I will post.

Based on the potential costs, I may be forced to buy a new car (or pre-owned) difficult to spend $1K+ on a mechanical issue on a 10+ year old car even though it has only 74K miles.

Update today: The car drove fine again today and the light did not appear.

Do you all suggest I leave it be and only go for the reprogramming if it comes up again? There were conflicting responses on whether the mom & pop shop and Nissan ECU reprogramming would be the same (MTZI30 - no and the converted - YES) so unsure if going to Nissan to get it done would even help.

[MTZI30]

Its a tough call. You got some low miles on it but 10 years of wear and tear, the car's gonna have some problems. Im kind of in the same boat. Cars getting up there in miles and age. Shes got a lot left but I do drvie a lot and eventually going to need to go another route. You really dont need to do anything unless your going to smog the car. Plus dont take my quotes above as exact estimates, just usually catalyst repairs can be pretty pricey.

[brushandcr]

Update: I had no error code for ~1.5 weeks and came back on again with 1 P0420. I am going to call up the mom and pop shop on Friday and find out if they can look up the TSB and let me know if they can follow or followed (or have the fix in their reprogram system. Worst case I will try to find a dealer that can do it for less then $110 and would be willing to examine/test the catalytic coverter and related parts at the same time (if possible).

[brushandcr]

Update: Over the last 2 months, the light has been coming on less frequently (one time in mid-March) and has not come back on for a month. About 3 weeks ago I went to the mom & pop that replaced the MAF sensor and said that it is possible that the computer needed to learn about the behavior of the new MAF even thought their flashes the EDU. The car is still riding good and hopefully the light is gone for good (or close to it). Hopefully this helps someone else in the same situation.

[loystock]

The re-programming at the dealership will most likely fix the problem since it involves changing the sensitivity of the ECU to prevent false warning. Other shops simply reset the ECU. Be sure to tell them the trouble code P0420 and they should be able to pull out the appropriate TSB for your car.