I need help in how to remove and replace the first sensor on bank #1 on my 5.4L. I can see it and barely see the plug connector above the sensor. I have tried to remove the heat shield surrounding the cat. converter but even by moving it back as far as it will go I can't reach the plug to disconnect the O2 sensor from the harness with the O2 sensor in place.

It looks like the wires are twisted and I am wondering if you don't have to remove the O2 sensor first to get to the connector as the dip stick tube for the Auto transmission is in the way. I have replace the other three but this one has me baffled.

By the way the codes I am getting are P0171 and P0174 after replacing the other three O2 sensors.

Thanks, Hugger94

 

I usually remove the R/F wheel and go in though the inner fender.
Or removing the inner fender liner makes it way easier and only takes a few minutes.
I press the tab on the connector with a really long thin screwdriver and use long needlenose pliers to pull on the connector and to plug it in again after.
If you remove the inner fender liner you should be able to do it by hand though.
Sometimes doing a little extra work can make the job go way quicker and easier.

 

So to ask a dumb question, I assume that I would have to remove the plastic trim around the wheel opening to remove the inner fender liner? I recall a couple of plastic bolts sticking through the liner on that side. I assume again that nothing really is attached to the liner except these two items? I had about given up on trying to remove & replace the sensor and run it to my mechanic shop with my tail between my legs like a whipped dog.

I do have some exhaust studs that have popped off which is causing some exhaust leak noise, could that be the source of my P0171 and P0174 error codes? My 5.4L has 146,000 miles on it and not idling evenly, it goes between 900 and 500 rather abruptly since I started replacing these other O2 sensor this last couple of weeks.

Thanks for the information!

hugger94

 

No you dont have to remove the wheel lip trim. You can pry it away enough to get at the screws. There are just a few screws and pushpins that hold the fender liner in place and you'll have to unclip the ABS wires and 4x4 vacuum lines from the fender liner if your truck has those.
To replace the exhaust studs you need to remove the fender liner too so you may as well do them while you're there. Pulling the manifold can be a bit of a pain but usually isnt that bad.
Theoretically an exhaust leak can cause the O2s to not read right but I've never seen it set a code. I think I'd be looking more for vacuum leaks.

 

Appreciate your advice, as I was able to get the O2 sensor replaced by removing the inner fender, using a pair of long needle nose pliers coming in above the frame rail and a long flat bladed screwdriver from underneath the truck to depress the catch on the connector. I felt like a surgeon operating, but reconnecting the sensor was a snap because I had determined what needed to be where to accomplish the task.

Guess what the check engine light came back on again after four starts. I have not stopped by AutoZone yet to get the codes ran again so I don't know what they are but guessing P0171 and P0174 again!

I don't know about those exhaust studs.... I may just bail and have a mechanic replace them, I would hate to totally disable my vehicle at my house without the proper tools to get them out or maybe end up taking the heads to a mechanist to extract them.

hugger94

 

Raceguy,


Just thought I would let you know that I think I have found the source or at least one of my sources for the error codes P0171 and P0174. I located the rubber elbow connected to the intake on the PCV tube. Guess what it was barely hanging on, basically the elbow had nearly broken in too. One little tug and it came off, after replacing it with a new PCV value assembly, tube and elbow the check engine light didn't come back on after 30 miles and at least four stops to shut off and restart the engine. The hardest part on replacing the assembly was getting my big hands back next to the firewall and working the remaining portion of the old elbow off the fitting.

Thanks for the advice!

hugger94

 

That's good to hear
It's becoming a very common problem. I'm glad it's quite an easy fix.