ive had a problem with my tacoma not running right.it felt off.so i tuned it up plugs wires,fuel filter, mass air flow,all three coils and both o2 censors, cat twice.once with a smaller on now a bigger magna high flow.the front cat is gone.it has a trd super charger.the truck had soooo much more power before.the code is 0420 and its pending.now a 0171 system too lean(bank 1)its also pending.my next idea is a a/f censor. dont know were or what. please help

I had a 0170 trouble code on my Tacoma. It could be anything from a vacuum leak, bad mass air flow sensor, bad O2 sensors, clogged injectors, etc. Lucky for me, it was only a bad mass air flow sensor and didn't cost an arm and a leg to replace.

When you say you changed the air flow, what do you mean? Did you increase air flow by using a high flow air filter or did you replace the mass air flow sensor? If you mean that you changed your air filter, then check your mass air flow sensor.

You say you changed out your catalytic converter with a high flow one, then it could be sensing too much oxygen (if you installed a high flow air filter) in the exhaust gases and tripping that code. Try putting a stock air filter back in the filter box and see if the code goes away. If not, check to see if the O2 sensors are operating within spec. If they are, then look at the mass air flow sensor and your aftermarket catalytic converter. It could very well be one of those two items.

There's a reason I won't mess around with a high flow air filter or the catalytic converter. The high flow air filter lets too many smaller particulates in that normally wouldn't get in if using a stock air filter. These particulates gets filter oil stuck on them as they pass through and gums up the mass air flow sensor. They then get into the combustion chamber and wears down your piston rings, which is why all suped up vehicles will eventually start burning oil and spewing grey smoke from their tailpipes. An aftermarket catalytic converter just don't last as long, or do the same job as a stock one, thereby causing other conditions like the ones that are plaguing your truck right now.

Hope this helps.

The P0420 code is you cat code. Meaning that its not performing to the specs the ecm is looking for. With the aftermarket cat on there if its brand new it could still be not performing to spec. and there for throwing that code. Dont worry with changing your o2 sensor all your going to due is waist 200 to 300 bucks per sensor. As for the p0171 I belive thats going to be the mass air flow sensor