I'm getting the P0420 CEL code even though I have spark plug defouler spacers on the secondary o2 sensor on my 02 accord. I'm thinking that the o2 sensor might be going bad because I've been using the spacers for a few years now without issue and now it suddenly isn't working. Any ideas on what it could be other than a bad secondary o2 sensor? Thanks.

 

more often than not, P0420 is a strong indicator for a "worn" cat. converter. the defoulers are more a band-aid fix. they blind the ECU to the issue, but don't solve the issue. that issue being a degradation of the catalyst to the point it no longer pleases the EPA. so it worked at first, but as the catalyst continued to weaken in effectiveness it overcame the differential readings between the two sensors and threw a code.

the real fix it to replace the cat. converter.

 

Or, if you no longer have a cat, it's time for a tune/flash to turn off the catalytic deficiency error code.

What chassis are we talking about here?

 

right, good point.

I'm just assuming it's the four cylinder.

 

Yeah its the 4 cyl SE sedan. I was hoping to avoid having to buy a catalytic converter but I guess I'll have to start looking for one. I graphed the voltage for the o2 sensor and its bouncing all over the place.

 

rockauto has decent stuff for around $160 + shipping

 

I would avoid roach auto at any cost: they will sell you wrong stuff and then charge you for the return shipping.

Sam

 

that cost is typically about 50-100% more from the traditional sources.

they will sell you anything you put in the cart... return shipping costs money, no?

 

Try and support local when you can. I always call my local parts stores, including the dealership, and see what they can do for pricing and availability. 9 times out of 10 they have the part on the shelf, or can get it next day, and the prices are usually close enough. If you can find a local parts store that has that personal customer service. They will look after you if they figure they can keep you coming back.