U Codes and Weird Sound at High RPM

Hey guys - not sure if this is connected, but I have the following U Codes: U0073, U0123, U0124, and U0126. I’m also experiencing a strange vibration/noise that sounds like it’s coming from the engine bay/under the center of the dash when accelerating and rpm >4000. I found this post on here for these codes that indicates a possible bad connector: https://www.tacomaworld.com/threads/can-communication-issue.571362/

anyways, hoping someone could help me out here. Hard to tell if these is a loss of power because the truck is so underpowered (I’ve had it since 2012).

Here is a video: https://youtu.be/DuHRYfosYWA?si=f5D8RP8mmzCzG31e

thanks!

 

I really don't think any of those issues are related.

Noises can be difficult to diagnose in person, over the internet it can be impossible. If you could post a video clip of said noise maybe someone would have some ideas of things to check.

What makes you suspect it's down on power?

 

Good call - here’s a vid: https://youtu.be/DuHRYfosYWA?si=LGTODMmScFq82itr

like I said, I’m not sure if it really is down on power since the truck is underpowered to begin with. It may be that I’m subconsciously avoiding higher rpm to avoid the noise so it feels a bit extra gutless.

 

I can't be certain but I'm thinking restricted catyletic converter and the noise your hearing is the backpressure overcoming the springs that hold the exhaust pipe up to the manifold and the exhaust leaking by.

You would have to remove the upstream AFR sensor and install an exhaust backpressure gauge to confirm.

 

Would that not throw a check engine light?

 

Nope, there's no pressure sensor in there to tell it if it's plugged.

I've never seen a plugged/restricted converter cause a CEL aside from sometimes a P0420/430 (catalyst efficiency low), main symptom is typically low/no power and sometimes a hissing/farting noise from the exhaust gases backing up and escaping somewhere rhey aren't meant to.

The 2 ways to confirm a plugged/restricted exhaust are a backpressure gauge screwed into the AFR/O2 sensor port or in-cylinder pressure waveform using and oscilloscope and pressure transducer.

 

Gotcha. When I floor it and it drops a gear (gears?), I do get more power and can accelerate still and pass cars when needed while the noise/vibration is occurring. Would that be indicative of a plugged exhaust or maybe something else?

 

Just depends on how restricted it is, I'm just going by the noise and that you said you thought it was somewhat down on power.
If you brought it to the shop with those symptoms exhaust backpressure is gona be one of the first things I check.

 

Appreciate the input.

 

So new info - this morning on the way to work both the TRAC light and the CEL came on. Had the codes ready again and came back as P0420 - catalytic converter efficiency. I’m thinking an exhaust leak? Or could just be my cat starting to plug off. 133,000 miles on it.

 

That further points to the converter, again the only way to know for sure is to test.

You may check with the dealer, there was a Special Service Campaign to replace the converter on 2010-2014 Tacoma's with the 2.7L so you may be able to get it fixed for free.

 

Wow that is great info, thanks. Any way I can verify if my VIN is covered or is the only way to contact a dealer?

 

You could try putting it in the Toyota owners website and see if it shows anything, otherwise yea you would need to contact a dealer.

https://www.toyota.com/owners/

 

You rock. Service campaign shows up for my VIN. Guess I’m calling Toyota tomorrow.