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I have a car that I’m trying to diagnose what’s wrong with it. Has P0420 code on it, ~120K miles (which is probably when o2 sensors should be replaced by now)
When I hook up my scan tool it only shows data for one o2 sensor but car has 2 sensors. One behind cat looks pretty crispy/rusty. Car runs pretty good otherwise. Once I delete code it comes back 2-3 months later. Don’t want to replace cat if I don’t have to and it might not be issue here. Should I replace rear 02 sensor first?
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Eric has a pretty good video about diagnosing a P0420 code…
This code does not cause drivability issues unless the Cat is clogged.
Sometimes the Cat is bad, sometimes it isn’t… Best to diagnose… Toyotas were known for easily throwing this code and did re-flashes for certain model years…
As far as I am aware, there is no TSB for a Re-flash of the ECM like they did on the 2003+ Corollas.
If you chose to replace the O2 sensor, only use Denso brand, trust me on this one.
There are ways to trick the rear O2 into not throwing this code, but they are illegal.. A google search will show you this way…
Also, be aware that some aftermarket cats can cause this issue right out of the box, even though they are working withing emissions specifications…
Good luck and keep us posted…
-Karl
I took some temp readings after driving it today. It definitely has hotter temps before cat and after cat it’s cooler so that makes me believe that cat is clogged to some degree.
I had that same code on my 2000 4Runner. took the Cat down and back flowed it with solvent and a water hose, then dried it well. Runs better now! Made sure the sub strait is intact! 😉
Which solvent did you use? I was thinking maybe I can use simple green or something in the bucket and let it soak overnight.
So I’ve replaced cat, put new gaskets on as well and I guess CEL is back on. Probably same P0420 code. What should I try next, maybe replacing rear o2 sensor?
Check the vehicle with a scan tool and CONFIRM it is a P0420. Try reseting the PCM or disconnect the negative battery cable for a couple of minutes and then drive the vehicle to get the code again. It takes a certain amount of time/speed to set the P0420 code, so it may come back…
Note as I said earlier, an aftermarket cat can cause the same issue and only use DENSO O2 sensors…
-Karl
Wanted to note that old cat was definitely pretty clogged up. I shined some light into it and there was barely any light coming out the other end.
There’s also another cat right after the header, it looks like a bit of pita to take off, but I might be able to clean it if its clogged up cause its over $300 for one of these.I used Brake Cleaner, flushing it well, then Grill Cleaner De-greaser letting it soak for several minutes. Back flowed with lots of water, then dried it very well. Inspect sub-strait before attempting this. Still running fine with no codes too. I started using Shell gasoline now. [quote=”mitmaks” post=83212]Which solvent did you use? I was thinking maybe I can use simple green or something in the bucket and let it soak overnight.[/quote]
Just confirmed P0420 code. This is for bank 1, so should I change precat or postcat sensor? Being that rear sensor is the one that measures cat activity I should replace back one?
[quote=”ToyotaKarl” post=83237]That is not a cat after the header, that is a resonator…
-Karl[/quote]
Are you positive? cause when I took exhaust pipe with the cat on it, and looked inside the header there was a “honeycomb” element. Maybe this is “california” spec camry :unsure:
This is how it looks like http://www.carparts.com/details/Toyota/Camry/EvanFischer/Catalytic_Converter/2001/REPT960310.html?TID=80000000CP&origin=pla&CP=1&CP_SRC=PPC&003=27372932&010=cpevcaco01toyotacamry19972001evanfischerrept9603101&gclid=CPCjj5ijxbsCFSISMwodEBkAdA
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