Ok, as you can tell, I am having the P1151 Code problem. Better start with the basics. I am the proud/frustrated (still extremely proud) owner of a 2002 F150 with a 4.2 V6 and an auto tranny, with 95,000 miles. I am have had the truck for 2 months, and now I am having Service engine code problems. The SES light came on, and I started losing power, and it decided to start binge drinking gas. At 95,000 I decided to throw a good tune up at it. Gave it a new Upstream 02 sensor in bank 2 (went with the P1151 code), new fuel filter (first time ever changed), new air filter, new motorcraft plugs (first time every changed also). Started it up and the light went out, power was back and gas mileage got better. Four days later leaving the parking garage after work and the light came on while sitting on a down hill ramp while stopped. Now it gave me a P1131 and P1151 code. Cleared the code and the truck straightened right out except for fuel mileage. Now another four days later, heading down hill out of the parking garage and the light is back on. I mean I checked every hose for vacuum leaks, checked the upper and lower intake gaskets, no leaks and look new. I really need help with this, it is driving me crazy, and I just want my truck back to normal. I guess my next check with be the MAF, but any help or ideas would be great. Any hidden vacuum lines or little tips that could clear my truck up would be great. I love my F150, I mean even on a bad day I can still out run a honda, and you can't beat that.

 

Its probly the MAF in one way or another. I dont know if it works with ford, but with other cars you can unplug the MAF and the car will switch over to speed-density calculations and it will figure out how much air should be running through the engine. If you do this and the truck runs great, its a MAF problem. I'm not sure what the codes specifically are, but i know that anything Px1xx is air/fuel related. IAC is another thing that could be the problem, but more likely the MAF.

 

Perhaps bank 1 is bad too? Perhaps you picked the wrong one...? It was 50/50 right?
P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P1151 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2
And I would check the MAF too.

 

P1131 and p1151 codes are almost always due to lazy/faulty upstream O2 sensors. Other causes are, indeed, possible, however, these codes are fairly reliable indicators of wornout sensors.

Start with some background:

Specifically, which sensor did you replace? Remember, there are four sensors on your vehicle.

Specifically, what did you use as your replacement part, ie, Motorcraft, Bosch, etc...

Vacuum and MAF issues typically post P0171/P0174 fault codes. The IAC valve usually only sets idle speed-related codes.

TSB 01-9-7 (available through the menu at the top of the page) provides in depth background information and tips for resolving these faults.

If you can watch the O2 sensor output on a graphing scan tool, the signal is much easier to evaluate.

Steve

 

Thanks to all of you for responding. I replaced the upstream on the drivers side (Bank 2). I only changed this one with a Bosch, because the only code coming up was P1151. It was after changing this one that I finally received P1131 with P1151. I did try running the truck with the MAF unplugged, and it ran a heck of a lot better, and quit trying to die at low idle. I am going to have to wait to get more in-depth with it till weekend, because I don't have a garage, and Ohio is getting our first real snow of the year today, and during rush hour no less...go figure.

 

Need a little more help. Ok, for the first time this week, Ohio broke out of negative temps and negative windchills, and I was able to check out the truck a little more. I disconnected the negative battery cable, and reset the SES light. Now I am able to hear something new. When I hit the gas, it makes a Gasp for Air, and then revs up...So now I am thinking vacuum leak. Are there vacuum lines that are hard to find, on the back of the motor, or that I might just be missing. I don't think it is the intake gaskets because after testing them, I can't find anywhere missing a leak, and I did have that problem with my old explorer, so it gave me a lesson in putting in those gaskets. Really any help one these vacuum lines would be great...If I can't find the leak, I am afraid I will have to go and drop a hundred on computer diagnostics, and I hate to let anyone else touch my truck. Thanks