I get this noise, sounds like a piece of tin can blowing across concrete.
Not very loud yet very annoying mentally.
Comes from the rear wheel area. Sound Familiar to anyone?

P0420
Had lean codes, extreme maf cleaning has cleared them for weeks.
Now the 420 has shown, think I should replace maf before sulking in a corner over the other option. I am gonna clean it again, and maybe some lead foot b4 wallet opens.

Oh, and the boot open light, Is there a clear write up on troubleshooting that, I did not see one in the quick links

 

When DTC P0420 is present, the catalyst on Bank1 (RH side of engine when viewed from driver's position) must be replaced.

You can waste time and money replacing oxygen sensors and cleaning the MAF sensor, but the catalyst is either damaged due to a misfire or the core has broken apart resulting in the noise you hear.

 

I figure on that. Is it the hard cat to get to?
I never had any misfires.
And the noise is only while moving, from the rear of the car.

 

Read this. It is Not necessarily your Cat going bad. So No it is not a waste of money and time to try other things. I had p0420 a couple of years ago and I replace the o2 sensor. I haven't had any problem since. P0420 DTC Code - Catalyst System Efficiency Below Threshold (Bank 1)

 

That is very interesting that you were able to clear P0420 by replacing an oxygen sensor. Which sensor did you replace?

I am interested in knowing how you accomplished that since that has not been my experience. I have seen individuals use 'spacers' on the oxygen sensors to not trigger the MIL, but that does not change how the catalyst functions. The vehicle will still fail an emissions test unless the catalyst is operating correctly.

 

Well the 0420 cleared, I did not even fantasize that it would be the overfilled gas tank that caused it, but appears so.
I never fill the tank, but had them dam grocery store points and packed it full and it was not 20 minutes later the light came on. Now that it has ran thru the test cycle again it has cleared. YEEHAA!
Finally got a clean code for my emissions test.

Now I am gonna work on the rear end, noisy, 170K miles.

Going to read now and see if the whole hub has to be replaced like the parts store shows for a wheel bearing.

 

Passed emissions!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Now I can fix the AC, wheel bearings, headliner, trunk latch, that dang rattle
And then buy another, I need a wagon for a pickup truck conversion.