CEL with PO420 code

I have a 1999 California emissions Maxima with 105000 miles. In July the CEL went on with a PO420 code indicated. My Nissan dealer wants to sell me a new catalytic convertor, but I am hoping it is something less costly. I have always used regular gas with no apparent problems. Could this be the culprit and besides changing to high test (which I have done) what else can I do? Thanks in advance. Ross

Yes, running 89 can cause issues with your O2 sensors. IIRC, 0420 is the downstream O2 sensor that needs replacing. It's within the cat and is easily replaced. Buy the part at www.oxygensensors.com and follow my directions: http://forums.maxima.org/showpost.php?p=2962352&postcount=16

~THT

yo im lookin to see if anybody can help me out on how to hook up a 1996 automatic nissan maxima im open to any advice

Try starting your own thread...

~THT

THT
Thanks for the info. I have ordered the rear O2 sensors. My Maxima has 2 rears. Waiting for them to arrive from Oxygensensors.com. The salesman was VERY helpful and I would recommend the company to all on this thread.

hey most of the time when u get a p420 or p430 its not an o2 sensors but its the cat yours would be the front flex pipe its salty but if have 80,000 or less miles on it its warranty

Hi all, I'm a new member with a similar problem.

Subject vehicle is a 96 GMC Sierra, 5.0 liter, 97,000 miles. I am reading a MIL code PO420-catalytic system efficiency below threshold(Bank 1). All the oxygen sensors seem okay, I see their outputs range from about .2 to .85 volts, and they seem to respond fairly quickly with throttle position changes. If the cat converter is bad, and I continue to run the vehicle will it effect the engine performance, fuel economy, etc? Is there any way to fool or permanently change the value the computer uses to determine the cat efficiency threshold. There is no vehicle emissions testing in the rural area where I live, and though I don't wish to be a ecological Neanderthal, the truck runs fine and I'd rather not spend several hundred in repairs if I can avoid it.

Thanks all