I was hoping someone may be able to shed some light on a problem I've been having with error codes related to the Bank 1 O2 sensor. I've been getting several codes related to the sensor, including P1131 and P1171, indicating a lean fuel mixture. I've done about everything I can think to do myself, including replacing air and fuel filter, checking for leaks to the best of my ability, and I finally replaced the offending O2 sensor as well.

Unfortunately, the codes kept appearing, so I took the truck to the Ford dealership thinking they could help. The only thing the dealership told me me, though, $90 later, is that the O2 sensor needs to be replaced again, which I just did myself 2 weeks ago. I'm skeptical, to say the least.

Does anyone have any other ideas? I've heard some people mention a fuel injector flush - anyone have any recommendations here? I'm just about to the point of waiting for the Check Engine bulb to burn out. I would have thought the Ford dealership would be more helpful.

Thanks for your help!

 

First let me say Welcome. Sorry I can not give you a quick answer but if you do a search on the topic there is plenty of info in here.
Good luck.

 

Try this:
http://www.fordf150.net/howto/throttlebodyclean.php

and this won't hurt either:
http://www.fordf150.net/howto/clean-...low-sensor.php

 

welcome to my world. if you have a faulty o2 sensor you get crappy gas mileage. i currently am getting 5mpg in my 97 f150. hopefully i can get it fixed, when i do i will tell you what they had to do.

http://en.wikipedia.org/wiki/Oxygen_sensor

 

Just an update on this for those who replied (Thanks!):

I tried cleaning the MAF sensor a couple months ago - didn't fix the problem. This week I went ahead and put on new ignition wires and replaced the O2 sensor again, as the dealer recommended ( I had replaced the o2 sensor just two weeks before taking it into to the dealership). I also snooped around the PCV valve. I'd been hearing a slight hiss where the valve connects to the vacuum hose. Actually, there's about two inches of hose that connects the PCV to the main vacuum hose. I'm not sure if this is how the lines were orginally designed, or if a previous owner did this themselves. Replacing that two inch hose did not get rid of the hiss, so I poured silicone sealant over the connection point - not sure if this will hold for long, though - I heard silicone doesn't handle gasoline well.

After a few days and a couple hundred miles of driving, the check engine light is still off. Not sure if I fixed the problem or not - time will tell.

Now to figure out why the hell the ABS light comes on about once a month!

4.2 liter '99 V6

 

I had a similar problem, but afraid I won't be much help because I ended up replacing many things that I planned to any way - all manifold gaskets ,polished insides of throttelbody, updated injectors w/the tall skinny ones(better spray pattern), New Plugs, Ford factory COP's - (not those Gantenelli's-overkill and need governing, or Motor-crafts, that do work). Rewired the harness to except updates and replaced just the one O2 sensor that fails the most out of the four - Upper Driver-side. Problem free after that ..runs as good ,if not better than new.

What O2 sensor did you replace? I can't believe you fixed the problem yet , but if so that's great!!! If you get a MIL again, from what I have read it seems that O2 sensor I replaced is the common one that fails.

Hope this helps in some way...

 

is your truck 4x4? i had a vacuum leek in the vac part that engages the front wheels. and that caused hissing sound,.

 

Well, the fun continues. The Check Engine light came back on again last night while I had been idling for awhile, then went away this afternoon after I had driven on the highway for awhile hauling a boat.

The most frustrating part about these O2 sensor codes is that they tend to be intermittent, going away and coming back again for awhile.

All of the codes are referring to the Bank 1 pre-cat sensor, which as I said, has been replaced twice. At this point, I'm thinking of trying one of these fuel system flushes that a few mechanics advertise these days, then giving up on trying to find a solution. I'm not sure if it's worth the cost in lost gas mileage to spend the money replacing all the intake gaskets and cleaning the throttle body, which I don't want to do myself.

The truck is a bare bones 99 4.2L v6 F150XL. No 4x4.

Thanks to all for the replies and suggestions.

 

Code P1171 = rotor sensor fault

 

Hey, just checking - did you remember to reset the computer after you replaced the sensor first and second time? Maybe it's an old code?

I also noticed that when I changed my O2 sensor, I still got the CEL light once or twice after I did it, but then it came good. I did reset the computer and it takes a few driving cycles to sort itself out and optimise its running, after first reset computer does a kinda sorta average of everything...

 

P1171 is not a valid code (doesn't exist on F-150 systems).

There's also no Rotor or rotor sensor on a 4.2L V6.

If, OTOH, he meant a P0171, he's got a vacuum leak that is affecting bank 1 only and all the new O2 sensors in the world won't fix that.

Steve

 

I am not sure if this will help or not. I have 262k miles on my 5.4L. I have never had a sensor fail. But what I found out last year when I had my truck inspected is that my tuner has turned off ALL of my sensors. The sheet had N/A next to each one of my sensors. Maybe if you cant get the problem fixed get a chip and have them turn off the sensors. My truck still runs great I get 19 mpg on the highway and 15 in the city with 3.73 gears.

 

Yes, you are correct. It was P0171, not 1171. My mistake. The other codes I've been getting related to this are P0133 and P1131. They don't all come on at once, but after resetting the computer by discharging the battery, at least one or two of them continue to appear after completing the drive cycle. Again, all seem to be related to the bank1 pre-cat O2 sensor.

And Steve, contrary to what you said, the diagnostic stuff I've found on the internet says that these codes could indicate a whole host of problems, not just a vacuum leak. See this link: http://limos.infopop.cc/eve/forums/a...2/m/5481099822

Is there anything that makes you believe it's definitely a vacuum leak?

 

After scanning the codes again this morning, I found both P0171 and P1132. As mentioned, I've had P0171 before, but P1132 is a new one I haven't seen before. Apparently, this one indicates a rich mixture, which is the exact opposite of the other code. I'm thoroughly confused...

 

It's not the O2's - the codes prove that they are working, It's the MAF, Vac sytm or Man Gaskets.

I had to dig deep for 1171 Steve lol - It's a Ford Generic code - Model unspecified. From back in the distributer days.

rundrums - what kind of air filter are you using?