Is this code p0420 rear bank 1 sensor located Upstream or Downstream?

 

P0420 is a catalyst efficiency code. Don't start buying parts till you understand whats going on. First, if you've got less than 8 years/80,000 miles, the cat is covered under warranty. If so, don't clear the code; the dealer has to see it. If you're not covered, the cheapest thing to try is several wide open accelerations, and some hi-way driving. The seafoam drive should do it. If you haven't seafoamed, do it. If the code comes back, try a can of bg44k in a quarter tank. Repeat the seafoam drive. If it comes down to buying a convertor, make sure you can get it warrantied. Also search p0420.

 

have a local muffler shop, a private owner place- ask for a cat and muffler inspection

Its usually free- they do a pressure and flow test to see whats needed, if anything
They have to document the reason for cat replacement to the govt- and these test must be included with the paperwork
Those guys know exhaust problems and can offer good advice

If you need do need a cat- our vendor Excelerate has standard and hi performace cats, the good one costing only 300, dealer wants 1000!

You could just need an O2 sensor, or maybe just the EGR ports are plugged and need to be cleaned- that will throw a low flow code too

Codes are NOT diagnosis~ they are CLUES!!!!!

remind us what year and current mileage- clean title?- not salvage/rebuilt car right?

 

if you get a hi flow cat like a RT Cat get a spark plug non fouler 'cus you'll need it. I actually had to use two to stop getting the P0420 codes and I replaced my 02 sensor in the process of the heater circuit fried.