O2 Sensor Lean

Been having issues with my 2012 2.7L 4cyl manual Tacoma. It’s been surging/ jolting for a bit without a code and it was driving me nuts. Replaced the plugs and didn’t help. It finally threw a P2195 code for the O2 sensor stuck in the lean condition. From the way the truck is running it does seem to be an air/fuel issue. Has anyone else had this? I’m thinking 1)bad o2 sensor, 2)bad MAF sensor, or 3) leak in air intake somewhere. Any help would be appreciated.

 

How many miles on engine and plugs?

 

Engine at 107xxx plugs are brand new

 

What brand plugs?

 

Bosch

 

You changed the plugs yourself? Allotta questions, I know

 

Yup. My mechanic hooked up his computer to it afterwards and they were all firing fine. The problem was the same before and after I changed the plugs.

 

Uh Oh.

https://www.toyotanation.com/threads/bosch-spark-plugs.404896/

https://www.tacomaworld.com/threads/bosch-spark-plugs.212970/

 

Plugs aren’t the problem

 

There is part of your problem.

Bosch I garbage.

Aside from that, while it is unlikely your plugs are the main contributor to your issue they can and will be an issue nonetheless. Toyota likes Denso/ NGK plugs.

You may want to get smoke checked for vacuum leaks because that indicates a stuck rich or lean scenario (I can't remember which) either way, you have to rule out vacuum leaks and incorrect MAF reading issues. Your next step would be to check fuel pressure to make sure that is okay as you have a 2012 and the pumps on 12-15 Tacomas were bonafide garbage as well.. you have to rule out fuel delivery issues entirely because it is likely that air fuel sensor is fine and it is just reporting an air fuel issue it is seeing further upstream.

 

I’m not sure there is a way to check fuel pressure on my engine without cutting any lines. If there is a way to do it that’d be great.

 

There is a quick disconnect fitting Right in the engine bay. You can literally pull it off with your hand.

Disconnect the fuel pump relay, give it a crank and wait until the engine dies and then disconnect the line to check your fuel pressure at that fitting. It should be on drivers side close by to the brake booster (most likely) V6 runs the lines there, I4 may be a different story.

 

I’m not sure that there’s the qd on the 2.7..

 

Do not dead head the fuel pressure into a gauge it will give you readings that are too high and incorrect.

Instead of the intelligent tester you can run the fuel pump by starting the engine.

Pressure should be between 40.8 to 41.7 psig

Maybe this will help:

 

I’ll give it a try. Thanks

 

I'd just put a sensor in it.. of you had a fuel pressure problem or an air leak it would be setting a 171

 

No it would not.

That's the problem with diagnosing without facts and just throwing the parts bin at it, you wind up spending a lot of money that may not even be necessary. Codes on a Toyota are usually just a symptom code, it is not the actual cause of the issue most of the time..

I have had a downstream oxygen sensor code which wound up being the head gasket.

It's not black and white with these vehicles sometimes. Most of the time on Toyota actually. He needs to rule out the basics and ensure proper fuel supply because an air fuel ratio sensor stuck rich could be a lot of things.

 

Theres more than 1 oxygen sensor in the exhaust stream though. An upstream issue would cause both sensors to get stuck lean. Thats an advantage to having multiple sensors, they can cross check each other.

When both sensors see a persistent lean issue it usually sets a p0171

The computer will do self-check strategies where it will drive the system lean in a hurry and then see if both sensors reacted at the same time and in the same direction. If one reacts and the other doesn't the computer notices. It will also do it in the rich direction. those are the p2195 / p2197 (stuck rich/ stuck lean)

The code is not trying to tell you the whole system is stuck lean, its trying to tell you that a specific sensor is stuck lean, even for just a few seconds. This is in the same family of codes as "sensor slow response" and it means the same thing, replace the sensor.

A 5 minute test drive with short/long term fuel trims pulled up on a scan tool would tell if you had a fuel pump problem or an intake leak.

If anything, I'd look for an exhaust leak near that sensor, but thats about it.

 

That's what you think... I understand how the computers strategy works.. and honestly.. the code means nothing. It's a reference starting point more often than not, nothing more. This has been most often the case on Toyota more than any other brand I have ever dealt with. GM coming in close second.

You really gotta check the basics before you start replacing crap. I don't mean you I just mean in general. It just leads to a lot less heartache, more cash in your wallet and it makes for a more thorough, better educated, well informed mechanic who knows without a doubt in their mind that one section or another is known good and has been tested to confirm that. It separates the YouTube mechanics from the real mechanics.

Might it be the sensor? Yeah.. anything is possible, but when it comes to lean and rich issues involving codes like that, what I have learned over the years is that it's all out on the table, especially when the indicated drivability symptom is surging.

If the air fuel ratio sensor is stuck lean, don't you think that there may be a whole lot of other crap above it potentially mudding up fuel control? I have had that exact code before on my own piece of junk and you know what was causing it? A cloggage of EVAP flow in the canister every time I would fuel up. I darn sure was not surging though, and it sure wasn't the air fuel ratio sensor either, but you see where I'm getting at I hope.

Do me a favor @Gunmaker96 pull the mode 3 freeze data for me from the scanner if you can. What is your indicated short term and long term fuel trim data?

 

You're saying you fixed a p2195 by replacing/unclogging the evap canister?