P0420 & P0430

Well...my truck has been taken over by these two elusive codes.

Both codes turned on within about 100 miles of my truck running out of gas (that's another story, my gauge showed 1/4 of a tank). It ran out on the side of the road near my parents house, and they brought me some gas - nobody knows the origins of that gas - small chance it was premixed with some 2 stroke oil. I only put about 1/2 a gallon in the tank and drove the truck to the gas station and topped it off and put just about 21 gallons into it.

Fast forward 100 or so miles and the CEL turns on. I cleared it with my ScanGauge but it showed up again about 50 miles later, and has been consistent, with both codes showing up every other drive or so.

I took it to the stealership and they said both cats are bad...not wanting to drop ~$2000 on a potential non-issue, I bought a Live Data Scan Tool and have been working on a diagnosis.

I followed the TFSM steps for diagnosing a P0420 and P0430, and watched the voltages on the A/F and O2 sensors. And both appear to be behaving normally (slight fluctuations around .55 volts). But when I check the Freeze Frame Data, the O2 sensors will both show a very low voltage ~ .01-.1 volts. Everything else looks good on the freeze frame - A/F sensors show near the same voltage, ~3.2 volts, the CATs are both running with a few degrees of each other @ ~1100 degrees.

Would you all agree that I probably have some "lazy"/slow O2 sensors? Any other ideas? I have also cleaned the MAF....and I can't find any exhaust leaks...

 

I would definitely replace O2's before dropping that much coin on some new cats. Maybe just but one O2 and see if that side's code goes away.

 

which cats? the headers cats or the two that are further down the exhaustpipe? I installed a full exhaust system new Doug Throley headers. Ionly kept two out of the 4 cats and installed the URD rear o2 stimulator. I have never had a check engine light. Butthat was only knowing that both of the cats that I had were in good shape. Try new o2s first

http://urdusa.com/Electronics-Rear-Sensor-Simulator/c66_170/index.html

 

if your truck has less than 80k miles on it, Toyota should (has to) replace them at no cost (but they wont tell you that if you don't know it). if it has more there are a couple tests/fixes:

1- turn the truck on and let it heat up. while it's running check the temp of the cats at both ends. if it is hotter at the back end (the "out" end) it's working correctly. if it's cooler at the back end, it's most likely bad.

2- spark plug spacers. buy a set of spark plug spacers (search the forum to find out the size) and drill them out to 1/2 inch. take out the rear two O2 sensors, screw The spacers into the holes where the sensors were, then screw the O2 sensors into the spacers. disconnect the battery to reset the codes. drive the Truck. if the codes come back, it's most likely bad sensors. if not, it's most likely bad cats. at about $6- this is also way cheaper than the O2 simulator.

if your cats are bad, you can:
1- pay the $2k (more if you live in CA...for the same part but with a "carb approved" stamp)

2-get a header and run spacers or the O2 simulators

3- just run with the spacers or simulator......it will even pass the california smog check (dont ask how I know)

***check the laws in your area before choosing suggestion 2 or 3***



on a side note: anyone have a suggestion on which headers I should get, DTLT or JBA long tube?