How to change Air Fuel sensor - P2197 DTC Code

Ok, first and foremost, be sure it's the sensor. A P219x code could actually be almost a dozen different things. It could be a relay, it could be a bad harness, it could be a bad computer. One of the most common causes is a vacuum leak (for lean conditions). There could be a reason you're running rich or lean. This write up assumes you're done some trouble shooting and ruled out everything else, it has to be the sensor. So here we go....

For this particular situation we're dealing with P2197 -
Oxygen (A/F) Sensor Signal Stuck Lean (Bank 2
Sensor 1)

Here's some reading material to look over that might be helpful: http://www.toyotapart.com/Engine_Bank_1_and_Bank_2A-F_and_O2_Identification_T-SB-0398-09.pdf

Bank 2 is the driver's side. The pdf's will tell you but another way to tell is bank 1 is always the front-most cylinder bank.

See how cylinder 1 sits slightly in front of cylinder 2? From what I understand that's a dead giveaway.

Tools needed:

If you're doing this yourself we'll assume you have a socket set with an extension. You may or may not have a breaker bar, but you may or may not need one. The only thing that is pretty mandatory that you might not have is an oxygen sensor puller or socket (7/8"/22mm) and you might want a thread chaser. Neither one should cost more then $5-$8. You'll need a deep socket to fit the thread chaser if you don't already have one. Here is another style of o2 socket that will also work:


First thing to do is spray a little PB Blast on it the night before. I hit it again the next day on my lunch hour too. I've read a lot of horror stories about getting these out.

Next it needs to be unplugged. Follow the wires starting at the sensor itself and you'll find the wire runs thru a metal clip keeping it supported so it doesn't melt. There are actually two. You can see the first one looking in thru the engine bay.

Wiggle the wire out of there. There's a second one farther back you have to get the wires out of also. It's so deep in there I couldn't get an angle to get a pic of it. It's exactly like the other one though. I found it easier to get at from underneath the truck, reaching up along side the exhaust.

Now it's time to unplug the harness. This wasn't bad but I had a second set of hands.

Here's the harness looking up from underneath the car, feet towards the bed. Just take your time and follow the exhaust, you'll run into the sensor. Then follow the wires to the harness. It's not hard to find once you find the angle on it. I was trying to wedge a screwdriver in the clip, I tried just flat-head bits, eye glass screwdrivers. I was having a hell of a time getting it unclipped. Here's where a second set of hands saved me a ton of aggravation. The problem I had was I could only get one hand at a time on the plug and couldn't unclip it and pull it apart. If you can, more power to ya. Skip the next few steps. The bottom line is it has to get unplugged, anyway possible. Here's how I did it.

Pop these two plastic tabs out from inside the wheel well and just let the rubber piece fold over.

The pic of the rubber pice folded down didn't upload right, but once you can see in there it's pretty easy to see what you were just working on. Feel around and follow all the pipes and wires again so you're familiar with where it all is. I still couldn't reach the plug. I still couldn't reach the damn thing. If I were by myself I would have taken the tire off the get at the harness. I really couldn't see any other way. Luckily, I had extra hands around the house.

Show you're helper the wire coming off the sensor and then get under the truck. Don't worry, you'll be able to see you helper's hands from underneath to make sure they got the right part.

Pinch here and have your helper give the wire a tug, it should pop right out. When you pinch the clip you should feel the clip open, somewhat like maybe pinching a clothes pin maybe? You'll feel the part your finger is on give and open up.

 

Ok, now we have it unplugged. Now to remove it. Most of the directions say to disconnect the battery before we unplugged it. The reason I didn't is because it's good to run the engine for a minute to warm everything up. Heat makes things expand. The idea is the manifold expands and makes it easier to get out. If you have any galling issues this will help the removal process. So that was my next step:

BE CAREFUL NOT TO BURN YOURSELF

Run the engine for a minute.It doesn't take long at all for that pipe to warm up. Then take your o2 socket and your extension and breaker bar or socket wrench and have it. Just slap it on there and go. You've unscrewed stuff before. It might be seized up though. Hopefully the PB blast and warming it up did the trick. If not a breaker bar will do the trick. I got a 1/2" drive, 25" long breaker bar at HF for $14 that did the trick nicely.

Now I disconnected the negative battery terminal.

You should be left with a gaping hole in your exhaust.

Clean it up some. Use a rag, not a paper towel, and clean up the threads of any PB blast and whatever. Now's where, if you had a bitch of a time getting the old sensor unscrewed, you'd run the thread chaser thru the hole just to clean it up. Being that I'm changing this at 30k, I didn't have any issues.
Here's the old sensor


And the harness side if you want to see more of what you're trying to unclip earlier


Now it's time to install the new one. I used a Walker brand sensor. http://www.walkerproducts.com/index.php/products/find-your-parts/It was about $60 less than NGK or Denso. Use whatever brand you prefer. I'll report back and edit this write up as to the performance of the Walker as time goes on.


Open up the box and CAREFULLY add a little anti-seize lubricant to the threads CAREFULLY. You don't need a ton.


Screw it in the hole where the old one was. Start it by hand, just make sure the engine has cooled enough. Be careful not to get anti-seize all over the place, especially on the fancy end. Make sure as you screw it in you guide the wires so you're not twisting the hell out of them.

The box says torque it to 35ft lbs.

Now it's time to plug it in. Run the wires back thru the metal clips and make sure they're good and snug so they're not going to touch anything hot or you'll be back under here again. The Walker sensor had a fairly longer lead so I ended up zip tying some of the slack to one of the hard lines it ran next too.



I put some dielectric grease on the new plug and it slipped into the connector no problem. Button up your wheel well, and reconnect your battery. This should have reset the CEL. You should be good to go. I've driven 30 miles so far and no lights, the truck is running much better and smoother, and it was about $500 cheaper than having it done by Toyota.


That's really all there is to it. Unplug it, unscrew it, screw in the new one, and plug it in.



Follow Up 02-09-15; So far, so good with the less expensive Walker sensor.

 

Rep for you man. Good write up.

 

Thanks. This was my first write up.

 

Good pics and writeup. I am adding this to my maintenance favorites folder. Probably never need to do it but you never know.....

 

op are the two front sensors the same or are they different

 

Yes, the sensors in front of the catalytic converter are the same on both sides. The sensors behind the cat are different than the pre-cat but also the same from left to right. As long as you have up-stream and down-stream right you're fine. For peace of mind you can go to NGK's website and see they use the same part numbers.

 

alright thanks man +1 for you

 

I just had this issue in my 2010 with 44k miles. Mine was on the right side and I did it alone. I removed the front wheel to do it alone and it was simple. This post was excellent. Thank you.

 

Threw the P2197 code just before a road trip. Ran good but seem to empty the tank pretty fast.

 

I replaced the driver side A/F sensor in my truck this weekend because of the P0051 code and I found an alternate way of disconnecting that wiring harness after attempting what the OP suggested.

If you have fat arms like I do, you'll find that you may not be able to get your arm far enough in from the driver's side to release the harness in back of the engine no matter which place you stick your arm. In addition, I think some Tacomas like mine have more crap in the engine bay near the brake master cylinder that makes it really hard to reach in behind the engine from that side.

What worked the best for me is to get up on a small ladder on the passenger side of the engine bay and lean over the engine using your right arm to rest yourself on top of the engine. Stick your left arm down behind the middle of the engine and release the plug while a second person pulls on the sensor wire from the driver's side.

 

Late to the party here, but is it possible that the sensor isn't reading correctly but doesn't trip the check engine light? I have no codes, but I get like 12 miles to a gallon combined..ive cleaned the MAF, new spark plugs, clean k&n cold air intake cone, I don't know what else it could be. The plugs when I replaced them were rich. Could it be the sensor about to go bad?

 

Did you have any luck? Im in the same boat and am basically 100% sure its due to a lazy sensor. However with no code i cant tell which one. All in all would probably be beat to replace both upstream.

 

Well, after 7 years and an odo reading of 94k I got my first cel on Monday morning. Trip to auto zone on the way home from work got me code P2197. Google/TW search got me this thread. Thanks for providing the part # op. It is still relevant and I found it on Amazon

$113 Walker Products 250-54006 4-Wire Air/Fuel Ratio Sensor

https://www.amazon.com/gp/product/B000C8ZJME/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1. Biggest pita of the job is disconnecting the plug. While the op went from below I didn’t want to bother dropping my skid to access from underneath. I ended up kneeling on the rad support and leaning on the engine to get my right hand shoved in to unplug. I reached in around the drivers side of the engine following the wire to the plug. My pic shows how I gripped the plug, with my index finger being where the release latch is on the harness side. I was eventually able to unplug it myself. I did the job yesterday, cleared the cel by disconnecting the battery and have run a bunch of errands today and no cel so far. Guess I’ll wait a few days before I’m confident it’s fixed correctly. Also, after resetting the clock, my stereo and seat belt chime I’m buying a code reader so I can read and clear codes myself and no more reset shenanigans.

 

On the 2010 Tacoma with a V6 engine, the sensors are different part numbers. Bank 2 (Drivers Side) is a

$131 Denso 234-9067 Air Fuel Sensor

Denso 234-9067. Bank 1 (Passenger Side) is a Denso 234-9084. If you lay the two upstream sensors side by side, Bank 1 wire length is about an inch longer.

 

With 130k on the 06 4.0, I think my sensor broke. I replaced the downstream and that didn't fix it so I'll try the upstream. Thanks for this write up.