Nissan Repair: Nissan 2001, oxygen sensors, threshold bank

Question
QUESTION: I have a 2001 Nissan Maxima. I bought it used at 45k miles. It now has 136k miles. For 3 years now, every year my service engine light comes on. I spend over $2k per year and the light returns after 6 mos or a year.  I can't get it inspected without the light off. I went to a garage and was told my catalytic converter has a leak and needs replacing as well as my oxygen sensors. I am discouraged because I think I am just being taken because its not fixed and I'm throwing money at this car every year. It runs fine and does not run any different after the garage repair. What would you suggest I do?

ANSWER: Hi Theresa -

Perhaps you have "nuisance" codes that pop up and cause the engine service light(SES)to come on. There are hundreds of sensors that can cause the SES light to illuminate, and you need a special reader called and OBD to get the codes. Once the codes are read, then you can start the repair.

Do you have that information? I will need the codes that were downloaded in order to determine what kind of problem you are having.

Alternately, you can have the codes erased using the OBD. Usually it takes a while for the SES light to reappear at which time you can get the vehicle inspected. I know you are not fixing the issue this way, but at least it will buy you some time.

Hope this helps -
aloha
calvin




---------- FOLLOW-UP ----------

QUESTION: Codes are: P0430 & P0420. I don't have what the codes were in the past year or two. This is what came up now.

Answer
Hi Theresa -

The code definitiions are as follows:

P0430 - Catalyst system below threshold bank #2
P0420 - Catalyst system below threshold bank #1

This means that the sensors are not reading the right parameters in both catalytic converters driver's side (bank 2) and passenger side (bank 1).

I know you said that you were told the cats were leaking and O2 sensors need replacing. In my opinion, I do not agree with that just yet. Because BOTH sides are getting the same reading, I would suspect the trouble is happening more up line, could be as simple as a vacuum leak.

Unfortunately I do not have the car in front of me so I cannot do the troubleshooting, so, please, as challenging as it is, find a trustworthy mechanic who will take the time to find the cause of the problem diligently rather than guessing on the parts that need replacing.

Hope this helps
and keep me posted
aloha
calvin