Code p0137

Hi guys! First of all, thanks for reading! Second, my truck is an ’05 Tacoma 4.0 V6.


I’m writing because I honestly don’t know what else to do. I’ve got codes P0137 and P0456 showing up. I’ve literally tried everything—even swapped the ECU—but here’s the summary:


I started with P0137, so the first thing I did was replace the sensor. Same code came back. That first sensor was a Denso, and it didn’t work. Then I swapped the sensor from the good side to the bad side and, surprise, the code followed the sensor. So the mechanic and I assumed it was a bad sensor.


Then I bought another one, this time Bosch—same exact problem. After that I was told to only get one from the dealer, so I went and bought one directly from Toyota (and as you know, you can’t return oxygen sensors, so now I’ve got a collection). We put that one in and still no luck.


I took it to another mechanic, and he told me that if the code follows the sensor like that, the ECU might be sending bad info, so I needed to replace the computer. Since the cats were replaced just a year ago, he assumed they weren’t the issue.


So I bought a computer, it was fairly cheap ($300, already programmed from a company in Long Island, NY, with lifetime warranty). I swapped it in, but the same code came back. At this point I’m so stressed I just have to laugh, but the real problem is my emissions inspection just expired today. With the check engine light on, I won’t pass.


Do you guys have any idea what this could be?

 

First off are you sure you changed the correct sensor? P0137 is for Passenger Side Downstream.

If your certain you changed the right sensor then you really need to look at scan data and see what the AFR and O2 Sensors are doing on both banks.
I have seen a skewed upstream AFR sensor cause downstream sensor codes but typically P0138/158 for high voltage.
It's also very possible it's a broken/corroded wire between the sensor and ECM but my first step would be looking at scan data.

That guy has no clue, whenever someone tells you to just replace the ECM for a code like that without doing any testing it's just a pure uneducated guess.
This shouldn't a difficult code to solve for someone that can do drivability diagnostics and test signal circuit integrity.