I thought I would offer my insight on trouble codes P0133 and P1131.

My problem was caused by a bad passenger side O2 sensor. The truck did not run funny and outside of the check engine light, nothing seemed amiss.

Replacing the O2 sensor was a frustrating job but manageable. You do not need an O2 socket to remove the sensor and unless you drop the exhaust pipe, I don't see how you could fit one in the tiny space. I intended to drop the exhaust pipe but I broke off an incredibly rusty yet securely welded exhaust flange stud. I decided not to try the second stud.

Undo the electrical connector first. You do not have a lot of room to work here. I used a long, skinny flathead screwdriver to push the clip's release in and pulled gently on the sensors wire.

To remove the sensor, You need an open ended 7/8" wrench. I sprayed the O2 sensor with PB Blaster twice over a 2 day period. You can see it from the passenger side wheel well. Not sure if it helped. I cut a cheap 7/8" wrench in half in an attempt to remove the sensor. This did not work as the short wrench did not offer the leverage needed to break the sensor free.

Lying under the truck, I wedged the full wrench over the exhaust pipe between the exhaust pipe and the heat shield. I worked the wrench onto the sensor and used a solid bar to push the wrench towards the outside of the truck. It's a tight fit and you have very little room to actually use your hand on the wrench, hence, the solid bar. You only need to turn the O2 sensor a quarter of a turn to break it free. You can then use your fingers or a short wrench to finish removing it.

Installing the new one is straightforward. Do not forget anti-sieze compound on the sensor. The wrench I cut in half earlier worked well for installing the new one. I installed it working from the wheel well, not under the truck. Probably could do it either way.

More notes on the code, I'm not a mechanic, but if your trouble codes show a problem with just one bank and the truck is not running poorly, you can probably rule out the MAF or a vacuum leak. I believe this issue would effect both banks.

 

Emsand1 Thanks for the info, I have the same two codes on my 97 Blue Ex!! It's 105 outside, I will try to tackle the job later this week maybe one cool afternoon. Picked up the 02 sensor from Autozone along with a can of PB Blaster. I will post back later this week with an update.

 

I need help. What's the best way to remove this sensor without dropping the exhuaust? It's a tight spot everything I try does not work my only options looks like dropping the exhaust...any tips I would appreciate.

 

After 13 years of rust, road salt and heat I was able to muscle off the O2 sensor B1/S1. All I can is be patient and take your time. Changing this sensor took care of trouble codes P0133 and P1131. I have been driving for a solid week with no issues and improvement in gas mileage....what a PIA



Detach the CAT might help to give you some play room in the tight spot....

 

i have the same problem on my F150, but i allready put in a new O2 sensor and the code still pops up. some times i also get a P0133. i also get the feeling the engine goes into safe mode as soon as the CEL comes on. gas/milage is a real horror.
i've allready put in a new fuel filter and injector cleaner, fixed a hole in the fuel tank. put in a new fuel tank vent vale that broke off, fixed the P1451 i had at first, checked exhaust for leaks, sprayed the engine with brake cleaner,...

i am getting a little frustrated cuz i'm allmost searching like for a month or so.

 

Check your fuel pressure, it sounds like the fuel pressure regulator is faulty or an injector or two is leaking.