I have a 98 ford f150 4x4 with a 5.4 and my cel came on so i had it checked at auto zone and the codes came up as po136 o2 sensor circuit malfunction bank1 sensor 2 and the other code was po141 o2 sensor circuit malfuntion bank 1 sensor 2 so i replaced the o2 sensor on the driver side behind the cat converter went back to auto zone to clear out my codes ,drove the truck about a 100 miles and the cel came back on took it back to auto zone and the same codes appeared has anyone had this problem before or know what the problem could be thanks

 

Bank 1 is passenger side.

 

those guys at auto zone told me it was the driver side if it is the passenger side is it the one behind the cat converter

 

Yes, sensor 2 is the one after the cat. It's not important anyway, all it does is monitor cat efficiency and does not affect the way it runs.

Autozone told you wrong. Bank 1 is the bank that contains cylinder #1, which is the front cylinder on the passenger side.

 

so a bad o2 sensor wouldnt make my rpms at idle waver a little and i have noticed its getting worse gas milage

 

It could once warm when the O2's take idle if their really bad. When cold it's all IAC.

let me get this straight , you changed your O2's and your still getting O2 codes? You should be getting around 16 mpg in 98.

The rear O2's have nothing to do with the motor.

 

the only o2 sensor i changed was the one on the driver side which was the wrong one ,when i get a chance i will change the other one maybe that will correct the problem or there might be something else wrong.

 

those almost never fail. I bet you have another problem.

 

Only if your getting codes, but it's a general to replace both forwards' at the same time. You didn't answer the codes question , so I assume your not getting them. If that's the case, you need to pull maintenance on your vehicle.
Go tru it. MAF, fuel filter, etc.. - Clean it up.

 

yeah im still getting the same codes

 

You guys are missing it, so I quoted the first post. Bank 1 sensor 2 is the passenger side rear sensor, he replaced the drivers side rear sensor because Autozone told him the wrong side, and is not surprisingly getting the same codes. Replacing the correct sensor will get rid of the CEL, but it won't affect the way the truck is running one bit.

 

Dang,Dang,Dang!!! AutoZone told me the same darn thing and I have been scratching my head wondering what the hell as I still had the same code after changing the 02 sensor! They said it was the rear one on the Driver's side and now I see it is actually the rear on the Passenger's side. And of course, I already threw the old one away!
Dang,Dang,Dang!!!

 

they probably didnt know that fords number 1 cylinder is on the passenger side, unlike others that the number one cylinder is on the driver side

get you a chilton or haynes manual, its been a life saver for me