Replaced the oxygen sensor hooked it up correctly did battery thingy to reset car and 100 miles later check engine light came on with same code... anything else need to be changed or could be the cause of it?

 

Whats the code?

 

do u have test pipes or hfc? if so, lol, and the code will keep returning.

 

Dudegetamoreinfo

 

Vague problem gets vague answer.

 

no exhaust mods whatsoever.

can't remember code but now the check engine light is back on codes are p0420 and 0430 which are both side catalysts.

I do not believe they are both bad at the same time something else must be causing the engine light.

gas mileage is averaging 16mpg when before my check engine light problem it was averaging 19mpg in the city.

what else could cause something like this.

I've run emission cleaners before and it keeps the light off for about 2-3 weeks and then it comes back on.

 

p0420 - Catalyst system efficiency below threshold Bank 1
http://www.nissanhelp.com/diy/obd_codes/p0420.htm

p0430 - Catalyst system efficiency below threshold Bank 2
http://www.nissanhelp.com/diy/obd_codes/p0430.htm

I am going to say you have bad Cat's. You may want to drop them and inspect them. They may be coming apart

 

yes i know but something is causing it besides the catalytic converters

 

Possible cause:

* Three way catalyst (Manifold)
* Exhaust tube
* Intake air leaks
* Fuel injectors may be faulty
* Fuel injector leaks
* Spark plugs may be faulty
* Improper ignition timing
* Engine Control Module (ECM) program

 

would you notice if the fuel injectors were bad or if the air intake was leaking?

 

The cats have an 8 year 80,000 mile warranty hopefully you haven't passed that mileage.

 

What have you recently updated/mod'ed?

 

subscribed for solution to problem

My CEL is on as well due to failed sensors in both banks

 

past that mileage currently at 117k

recently changed oxygen sensor cuz code kept coming up oxygen sensor before that was shocks and before that was control arms... that's as far as i can remember back. spark plugs were changed at 100k so was pcv valve and valve cover itself.

 

I'm guessing a broken cat, but check for air leaks, bent exhaust pipe and bad plugs. Possibly even bad packs. The fact its throwing both banks codes bother me. If it were throwing one, a bad cat would make more sense but the odds that both cats went out at or around the same time is odd. That makes me think something may be off alittle further backward up the sytem, such as with the fuel system but that should have thrown a mixture code as well. Also check to see if you bottomed out on the cats and possible broke them that way. Generally you can hear a rattle if the cats are bad, plus you'll generally feel a power loss.

 

no power loss just up with gas mileage i did hook it up to a live data code reader in may and it showed that both the upstream o2 sensors were running rich but before changing out my right side one last week i pulled the code and it was just showing it for that one.

 

Why is it impossible to believe you need cats @ almost 120k? If both sensors are switching back and forth and almost mirroring eachother you have bad cats. The rear O2's should hover around .5V on a perfect running car.

 

Ive seen someone on craigslist selling their cats for under $200

 

if there is a leak, spraying carb choke cleaner or brake cleaner all around the plenum flange will cause the rpm to rise

not sure how to check injectors

 

because what if its not the cats

i'm trying to go by what costs the least and if at the very end i need to buy cats i'll buy em but if its not them and i spent $200 + install i will feel