flykrs1

2000 4Runner California Emissions.

My check engine light has been going on and off over the last few weeks. I finally determined it was the dreaded p0420 code. It went off before I could get it to Toyota (still under Fed Emissions warranty). My truck has TRD headers (welded to cats for some reason, toy did install) and TRD Exhaust. The light finally came on again this weekend and I took the rig into Toyota Monday. They found the problem to be a cat. Then they accused me of replacing the stock cat with an aftermarket because they did not recognize it. I told them to check their facts again. So this morning they determined the cat to be a Toyota brand and also told me that both O2 sensors need replacing for $800ish. From what I have read I am not sure they can determine if the O2 sensors are bad until the cat is replaced.

Any help is greatly appreciated, thanks.

Greedy

"IF" you need both sensors (AFR and O2) get them from urdusa.com and install them yourself. It will probably run you $300 ish in parts and about 15 minutes of your time.

MTL_4runner

They are basically trying to cover their butt and get you to pay for it at the same time. The P0420 code can be caused by a few things but the 2 main ones are the O2 (front one is an A/F in your case) sensors and the cats. Usually you would replace the O2 sensors first since they are the cheapest parts and then the cats last since you would have narrowed down the problem. In your case since it is still under emissions warranty, they are trying to get you to do everything at once to ensure that if they do replace the cats, the CEL will go out (ie they tackled both the potential problems at once, pure blanket parts replacement). If it were my truck, I'd do as Greedy mentioned......have them put in the new cats and buy the parts from URD (few other places on YT as well) then put them in yourself for maybe $300 or so.

ebelen1

Weird thing for me was that PO420 came up first. Cleared it and then a PO171 came. After replacing my MAF, the code went away. Have you tried resetting it and then checking the code again?

flykrs1

Thanks for the help. I am sure they didn't do the voltage checks on the sensors, I didn't know if it would be worth it to do the checks myself or not.

I have cleared the P0420 once previous to this CEL and it came up the same this time. I've got 79k and according to a couple other posts thats not bad for O2 sensors.

Elton

Welcom to YotaTech ... try cleaning the maf sensor and see if that helps and also i have 135k on stock oem o2 sensors