2002 Tacoma 3.4, third brake light/electrical issue

Hey guys, first post here. I was dealing with some electrical issues recently(Had a P0302, and then a P0303/Random misfire error code) so I swapped a coil, didn't work and took it to the dealership. They cleared the codes, shrugged and said maybe I fixed the problem with that one coil change. Few months later now, I'm getting a P0420 code, catalyst system issue but not a specific bank, so idk if it's a sensor issue or the Catalytic converter itself(Aftermarket after theft). My third brake light as well as my driver side brake light went out, so I replaced the driver side with new bulb, and it works. But I'm scratching my head wondering if the 3rd brake light issue is actually a bulb or something internal, because I can't see how all 3 bulbs just go out?

 

unrelated

but
i have done this trick on a Subaru/Honda/Chevy.....without any issues
i still own/drive the Subaru (226kmiles)

from what i gathered, the CAT will throw CE lite if CAT is working below 90% efficiency
that 90% works for me.

https://www.youtube.com/watch?v=J1pOJ1Hn-wQ

lots of vids out there

 

So you're admitting to (edit: 3 counts of) fraud and an advocate for illegally modifying your emissions system. Nice.

"So this will trick it to think that the catalytic converter is efficient." sure sounds like it fits "attempts to fraudulently obtain a smog check or inspection".

 

90% efficiency
when i went to school, that meant i got an A in the class.

????

 

If your state has emissions standards, and you have intentionally modified your vehicle to pass inspection, that is 100% fraud. The law doesn't really mention or care about what grades you got in school.

Furthermore, telling people you have done that on the internet and explaining how to do it is just plain stupid, not to mention against the TW terms of use (regardless of whether or not your state has emissions standards). Specifically:

 

It's a bummer that the dealership didn't help you more.

I think you have a few separate issues going on.

The misfire codes - If you haven't done wires and sparks plugs in awhile just start there. Followed by the injectors, and finally the coils if not resolved.

Catalyst system - prolonged misfires can cause damage to the cats, but that doesn't seem likely if those were relatively recent. That being said, cats aren't life long items, and looks like you've already changed yours out due to theft. Do you know what cats you installed? The CA spec cats cost more but are more efficient. I believe every truck after 2000 or 2001 got CA spec cats regardless of the state they were sold in. There could be a few things here- the "new" cat might just not be up to spec enough, older than might think (aka, when was it installed?), or they may have been poorly installed and there is an exhaust leak allowing for a false reading. I'd look into that last one first.

The light systems are ground switching on these trucks, and notoriously have issues... If you have a trailer harness, that's a typical culprit. If not, start by inspecting all the grounds associated with the tail and third brake lights. They might just have some corrosion on them.

 

Sick thanks man. I called my insurance to see if they can cover me taking in my truck to get a diagnosis on their dime since it was them who replaced the cat, sounds like they will do it. I did have prolonged misfires and sat(and drove) with that P0302 code for a few months, so I could have done it by just not servicing it in time.

As far as the light systems, it's all stock so no trailer harness. I noticed some corrosion on one of my headlight sockets, after figuring out it wasn't a bulb issue either. Where could I find out where those grounds are located?