Another Check Engine Light question (with code)

my CEL light came one, i scanned the codes, i have a code P0420!
checked what the code means- catalyst system below threshold.

a code website says it could be: o2 sensor, catalytic converter gone bad, engine coolant temp sensor, exhaust leak...

any tips on checking things out? which should i check first? how do i check my catalytic converter and o2 sensors?

the nice thing is that the code website says its something i can drive with no problems!

 

PO420 means the catalyst efficiency is below the threashold determined by the EPA, basically the internals of your catalytic converter have deteriorated to the point where it is not burning off the excess unburned fuel from your engine. Unfortunately the only fix is replacing the converter. You can go to an exhaust shop and have an aftermarket one put it, trust me its loads cheaper than going to the dealership, however, aftermarket ones are not built to the same standards as ones built by toyota and there is a chance that your check engine light will come back on. Im actually a toyota technician and ive seen in many times. So if you want my opinion.. take it to the dealership, you know it will get fixed right, instead of spending money twice. Some things you can go aftermarket, but sometimes its best not to.

 

what kinda price are we talkin?

 

Good luck with that one! My dad had that on his '96 2.4l and he could not get it to go away. Replaced the WHOLE exhaust system and oxygen sensors. Checked EGR valve and vacuum and whatever else emissions related. If you can do the labor yourself, it's cheaper than having a shop do it. Especially if you end up shotgunning parts at it.

 

Here ya go: Check there. Good starting place.

I threw a 0420 after replacing the O2 sensor. I think I fixed it by removing the O2 sensor and cleaning (wire brush) the mounting location real well. I also tightened my exhaust clamps (aftermarket exhaust).
That code is your O2 sensor telling your computer that the reading it is picking up (the gases in the exhaust) isn't what it should be. That could be corrupted by a leak in the exhaust system (like mine was in the new sensor mount and exhaust clamps). If you did work to your truck recently, you might be lucky and that is your fix. You might find a small hole in the exhaust. It could be that your O2 sensor is dying. See the link above to test it.
Start by checking the exhaust system, then test the O2 sensor. Many people here get the sensor from Rockauto or Amazon. Good luck!

 

on thing i noticed on the truck (96 2.7l) is that there is a hose running from the air box over the other side of the engine into the evaporative canister dealy (i think thats what it is) and there is a crack on the airbox side, not giving it a good tight seal. obviously i plan to replace this hose, but is it something that could be causing this code?

after i replace this hose, do i delete the code, or will the CEL go off on its own if the problem is resolved?

 

sorry for the elementary question, but what is a reliable method for detecting exhaust leaks?

 

Seafoam works very well. Use an intake vacuum line to slowly suck it in the intake while giving the engine some gas. It will smoke a ton and show leaks. Or...
Soapy water. Spray it on all flanges and around the EGR and manifold.

 

I just had that code last month and it was the o2 sensor's.

I would first check for any leaks, and if none. Then pull the o2 sensors and see what they look like. If there black and look like they have some burn spots. then there toast. get new once. And then go from there.

With the cats. You can tap on them and if they rattle, then there going bad. And also you will smell a wrotten egg smell from your exshaust if there bad.

Good Luck!

 

still searching for the problem...

i fixed the cracked hose the runs from the airbox,
scooted underneath the truck, both O2 sensors look pretty new, i didnt pull them but they have clearly been replaced at some point, very clean. also i think i remember the previous owner saying he replaced them, he took care of the truck. i whacked the catalytic converter and it sounds good, no rattles, my exhaust doesnt stink. have not done a thorough searched for an exhaust leak yet.
heres something else that might be linked... my vapor canister "toots" A LOT when the car sits....maybe related?

but here is my big question:
should i have erased the code when i scanned it to see if it comes back?