2010 Tacoma has the P0420, RPM drops at -30MPH speeds, and is blowing hot air.

2010 Tacoma 4WD 4L V6 with 296K Miles.

On the way home tonight I was going up a hill and after I made it up I saw the RPM jump up a bit and the truck started blowing hot air from the AC vent, I even turned on the cold air and that did nothing. I saw the check engine light come on and a minute later I hear a clunk/or something similar. I made it home 10 minutes later and checked the code and I got
P0420 Catalyst efficiency below threshold (bank 1)

The engine temperature did not increase on the way home. I have also noticed that when I am driving under 30MPH the RPM will drop down for a second and it feels like the engine needs some more power when that happens but it jumps back up to where it left. It feels a bit strong for a standard downshift in my eyes. I could be mistaken.

I plan on taking a look at the truck in the morning.
With these symptoms in mind, Mainly the P0420 and hot air blowing, where should I start?

 

Iss that the ONLY code? Those a/c vent stuff is crazy for a po420 catyletic related code.

 

Yeah that was the only one. The only thing was that the code popped up twice. But both say P0420 with the same exact message. :/

 

UPDATE: I checked the truck this morning. I have not taken it on a drive yet but the vent is no longer stuck blowing hot air, I wonder if it only happens while I drive the vehicle. I checked hot and cold and all the fan speeds, it was all normal. I will update this post again after driving it. The P0420 still remains.

 

Have you ever replaced your cats in those 296K miles?

 

I do not think so. Before I started driving it, it was my Fathers. I am 99% sure he never changed any of the catalytic converter's.

 

Mine didn't make it much past 100k miles. I think yours have had a good LONG life. Good chance you need new ones with the P0420 code.

 

is there any way to test a cat or is that kind of equipment only going to be in a mechanic shop?

 

No way that I'm aware of, but i'm very limited in my backyard mechanic skills. It was way beyond me, so I took it to a trusted off-road shop I use.

I will note that I hoped it was a sensor, so I swapped the O2 sensors after the cats from the left to right side to see if the problem followed the sensor, but it didn't. If you're actually seeing performance issues, though, I'd be more inclined to say it is definitely the cats.


I have heard of this, but I don't have an infrared thermometer:

Temperature check with infrared thermometer:
Compare the temperature at the inlet and outlet of the converter, the outlet should be significantly hotter

 

I think these are two seperate issues

 

When I ran into that P0420 code I bought a BlueDiriver OBD2 scanner from Amazon and used it and my tablet to check the actual values the 02 sensors were producing and see what that told me.

BTW...here's the Bluedriver $99:

$90 BlueDriver Bluetooth Pro OBDII Scan Tool for iPhone & Android - No Subscription Fee - OBD2 Car Scanner and Code Reader - Diagnose Check Engine, ABS, SRS, Airbag & 7000+ Issues on Vehicles 1996+

https://www.amazon.com/BlueDriver-B...33234&sprefix=blue+driver+obd2,aps,142&sr=8-1

Anyway....to get a P0420 code your taco goes through a long sequence where it first verifies your O2 sensors are functioning and then compares the readings from the two, calculates that cat efficiency and compares it to a standard. If it doesn't meet the standard it kicks out the code. Anyway...in checking that bluedriver, I was able to see that my cats were far-far-far below passing. It was like they basically weren't working at all (125K miles).

At that point I looked online and found a Walker brand replacement Cat assembly for about 1/3 what the Toyota OEM unit was and planned on installing it myself. Then, based on someone here mentioning that Toyota had put out a recall on bad cats at some point, I ran my vin through the toyota sight:

https://www.toyota.com/recall/

Where I found my truck DID HAVE an outstanding recall. Called my local dealer and they ordered the OEM Toyota parts and installed them on my truck...for free....even provided me with a loaner for the day it took to get them installed. That was 2 years ago. Check engine light has never returned.

Good luck!

 

UPDATE:
That clank was a misfire and it only got worse over time. I cleaned the throttle body (attached image so you can see how bad it was lol) but one can later and I was only able to clean around 2/3rds of it. But after that my idle RPM was very high. Next I replaced the spark plugs on the passenger side ( 1 | 3 | 5 ) and that has stopped the misfire and returned the idle RPM back to normal. I think the Cat code was just the misfires wearing away at the poor thing for so long. To this day I do not know what caused the hot air issue but that still has never happened again. I also have not felt any unusual RPM drops so that was likely coming from the old spark plugs as well. I still have A LOT more maintenance to do but for now it is running better than it has in several months.

 

P0420 bank 1 code is for cat efficiency. With that many miles it has likely failed/partially clogged since you mentioned you’re experiencing some bogging. If it’s clogged it will be getting very hot. My buddy’s mazda3 was partially clogged and was literally glowing red at one point.

I’m dealing with the same code, replacing my cat next week