I don't see many of these successful fixes posted, so let me share my story:
2009 F150 with the 4.6l (code W) V8 engine, 4WD, Auto trans. 26,000 miles on it. The check engine light came on last week and I'm not the type that likes to take a vehicle to the dealer. So I bought a code reader (about $100 at Autozone) and read out the code. It was a P2197 code, which is Oxygen Sensor Signal Biased / Stuck Lean Bank 2 Sensor 1.
Looking at the fuel trims, they didn’t seem way out, but the bank 1 matched the bank 2 exactly. I assumed that this was just the computer’s way of dealing with a bad sensor. Ignore the bad one and set both banks to the same as the good one. The bad one was stuck at an EQ ratio of 1.999, which is basically the maximum lean reading. It never seemed to move. The other sensor varied around 1.000 as it should. So either something was causing a very lean condition on only the driver’s side cylinders, or the sensor was indeed bad. I poked around under the hood and listened and looked for anything that would explain a bad vacuum leak on only the driver’s side. I didn’t see or hear anything. I also used a mechanic’s stethoscope to listen to the injectors, and they all sounded the same. So I was pretty convinced that I didn’t really have an extremely lean condition on the driver’s side, while the passenger side worked fine. I guess there is a lot of other things I could have tried to verify that, but at this point I rolled the dice and bought a new sensor. It was about $100 at Checker (O’Reilly) and was the exact same Bosch sensor with the exact same plug as the OEM part. It was pretty tight clearance getting it changed. Luckily my hands are not very big. I was able to use an open end 7/8” wrench to remove and replace it. The hardest part was unplugging it from the harness. I could only get one hand in there at a time. I thought I might have to drop the front drive shaft to do it, but I finally managed to disconnect it. Installing the new one was easy. Again I used the open end wrench, so I just guessed at the torque. I bought a sensor socket (actually a crows foot) but no way to get it positioned to where my torque wrench would do any good. So I snugged it down to ‘exactly’ 30 ft-lbs, ran the engine for a couple of minutes to get it pretty warm and then re-snugged it.
To my delight, the new sensor reads good. I cleared the error and took it for a good long test drive, and it continues to be good. I probably got a bit lucky. I didn’t really rule out every possible thing that could have caused a lean condition, but everything led me to believe that the sensor was the issue.
I also got lucky on the code reader I bought. I went in not knowing what I wanted, so I was just going to get a simple reader. But luckily I ended up with one that showed real time data. That helped a lot to convince me the sensor was the issue. Seeing the fuel trims and the sensor readings moving was great. A logging one would have been nice, but I just snapped pictures of the screen with my cell phone to ‘record’ the readings.
One final thing. I bought a Haynes manual for the 2009 F150 and it is worthless. There is almost zero specific information on the vehicle. It is more of a generic repair manual. The only thing I could even use it for was to check for the location of the number 1 cylinder, but even that was ambiguous. No indication of if you were looking at it from the front or rear. I had to use the internet to be sure. Would labeling the diagram with a “Front” have been so hard? The wiring diagram are a joke. The instructions to change the sensors are – Unplug the old one. remove the old one. Install the new one. Connect the new one. Gee, thanks. Very helpful…..NOT!
Save your money.
Nice job Terry.
I do this for a living and although you may have gotten lucky on the "code reader" that gave you some "live" data too, you approached the repair with an understanding of the pitfalls and avoided them nicely.
Thanks! I know I lucked out, by it was at least a calculated gamble. Now that I have been done this path once, I can see the wisdom in spending the extra coin for a reader with logging capability. But then again, I wouldn't be unhappy if I never get the chance to use my reader again (since I don't make a living at it).
Good job Terry...glad to hear you got it all worked out. I have been kicking around the idea of getting a code reader for my Sequoia because I have all sorts of lights on (my traction control, abs, etc.) for a long time now. The brakes work fine etc. and I have brought it to Toyota and spent some coin on them trying to figure out what it is.. They said "Oh it came back with some HARD codes (well duh!) but couldn't pinpoint what the part really was. They said most likely it is the main brake controller which is a $2500 part from Toyota I did fine that same part (if that is what it really is) for $350!!!!!
I have yet to replace it but want to get it replaced soon. I wonder if the code reader would really point me in that direction?
Rob, disabled VET USAF.
My Mod Thread 2013 F150 Platinum, Ego-Boost, 3.73, max tow, skid plates, and bed liner, 32% ceramic tinting.
2016 Explorer Sport-3.5L EGOboost!
The code reader is just a tool. It lets you know the code, but for that to be useful, you need to know what that means, and what things could cause the issue. There is lots of good information on the web, but it takes lots of time to weed through it. I spent quite a few hours on the web looking at what could cause my lean O2 reading. I got a bit lucky, or else I could have wasted $100 replacing a perfectly good O2 sensor and still had the problem. In my case, the issue was pretty obvious, but if it was more subtle, I could have wasted both time and money.
I was able to repair the ABS on my motorcycle (yes, ABS on a motorcycle) for $100 in used parts instead of the $2200 (parts only) that the dealer wanted to fix the problem. So if you are motivated enough (or cheap enough) and have the time to spend doing the research, I think most problems can be fixed by the shade tree mechanic.
I seem to remember that some code readers include the ability to read ABS and air bag errors, but not all do.
Glad you got it all figured out, but 26,000 seems awfully low miles for the sensor to go out. Sure it could very well be an anomaly, and it more than likely is. But couldn't something else have made the sensor go bad in the first place? Just a thought. I don't know what would make it go bad, but it may not be a bad idea to run a scan for latent codes that do no trigger the CEL, and which normally cannot be read with the $100 Autozone scanners.
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I too have a 2009 with 4.6. The check engine light came on and I borrowed a code reader which gave me the P2197 code. While driving around with the graphing code reader plugged in you can see the values for the various O2 sensors moving up and down. I also found one bank to have an EQ ratio of 1.99 while the other bank was around 1.01.
This all leads me to think that one bank is lean (intake manifold leak?) or I've got a bad O2 sensor.
My problem is at "bank 2, sensor 1". From the above post it looks like bank 1 is drivers side and bank 2 is pass side? Can anyone confirm that? TIA
Mine was also bank 2 sensor 1, which is the drivers side, upstream sensor. Reading a bit, there are many things that could cause this fault besides a bad sensor. But it is hard for me to imagine that anything could cause one side to read full lean, while the other side reads spot on. Just to be sure, I poked around under the hood looking for anything that would cause a vacuum leak. A hose pulled off or something like that. I also used my cheapo mechanic's stethoscope to listen for all of the injectors 'firing'. They should all make a nice distinct ticking sound, and all sound the same. If one wasn't working it might explain a lean condition on only one side.
Driving around while whatching the sensor reading, mine never came off 1.99 (max lean), and the truck ran well otherwise. Also the fuel trims were the same on bank 1 and 2. All of these symptoms together made me reasonably sure that it was actually a bad sensor. At least sure enough that I was willing to gamble the $100 for a new sensor. There is still probably many other things that would cause the bad reading besides a bad sensor, so that's why I say I felt lucky that it was indeed the sensor on mine. I guess to be even more sure, you could pull the spark plugs and look for any signs that one has been running way lean compared to the rest.
I suppose another idea would be to switch b1s1 & b2s1. If the problem switches over to the other bank then it would almost have to be the sensor. I think I'll just change the sensor. I'll let you know what happens. Thanks again.
I also considered swapping bank 1 and bank 2 sensors. I wasn't sure if they were the same part number or not (maybe different cable lengths?). Good luck, and let us know how it works for you.
BTW, one suggestion I read was to warm up the engine a couple of minutes to make it easier to loosen the old sensor. Of course then you have to be carefull not to burn yourself. The hardest part for me was disconnecting the connector. I have 4WD, so the front drive shaft was in the way. I almost thought I would have to remove the drive shaft, but my hands are small enough that I could get one hand on it and managed to unplug it. I practiced on a connector under the hood that I could get to easily so I could understand the way to release the catch.
Changed the sensor and it worked! The check engine (MIL) light has stayed off for several days.
Just a few notes: 1) the old sensor was tight! a 7/8" end wrench fits but is very loose, a 22 mm wrench is a good tight fit, 2) I ended up going to NAPA and getting the O2 sensor tool - like a socket with a slot but offset square tool hole like a crows foot. That worked for me, 3) it was a pain to get the old wire out but the whole operation was very doable at home. 4) the new sensor was not in stock at NAPA and would have been over $200, it was in stock at the local dealer for "only" a $129.
I normally wouldn't condem a sensor so quick but in this case it was easier to change it and I got lucky.
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