6. Disconnect the wiring. There is a small tab that has to be pushed in on the male portion of the plug, then pull down the plug. I had a little bit of a hard time getting this, so I used the pointed scratch awl type screwdriver to stick into the tab, then pull down. Remember, don’t pull too hard because you don’t want the female part of the plug coming off the block (mine didn’t so I don’t know what will happen if it did. Just didn’t seem like it would be a good idea).
7. Once the wiring is disconnected, put your socket onto the sensor. There is a gap in the socket to slide the wiring into and the socket slides right onto the sensor. The socket portion is only on one side of the socket, so make sure you have it facing the right way. You want to adjust the socket so that the leg sticks out above the exhaust pipe, like this:
8 . Next, I ran my long (18” I think) 3/8” drive extension to the socket’s leg, straight out towards the tire. I then used a 1/ 2” to 3 /8” adapter to attach a 1/ 2” drive ratchet to the extension. You could use a regular 3 /8” drive ratchet or 3/8” breaker bar, but my 1/2" drive ratchet was longer and gave more leverage. The below pic shows how I ran this out (notice the tranny dipstick tube hanging there):
Now, THIS IS IMPORTANT!!!! Because the O2 socket is facing away from you, the old adage of “right tighty, left loosy” DOES NOT APPLY here. If you have your ratchet set to tighten a normal bolt, you will never get it loose. If you think the O2 socket is super tight, stop, take a breath, and check your ratchet direction. As I said above, I did this job cold. The sensors were original (I believe – they had Ford stamped on them) and had 114,000 miles. They loosened up pretty easy.
I gave it a good tug on the ratchet and it popped loose right away. It was not difficult at all. Your socket will bind up against the exhaust pipe, so you will have to back it off the sensor, adjust it, then turn it some more. After a couple of turns, you reach in with your hand and finish backing it out. Sensor is out.
Old sensor versus new sensor.
On my 1997, 5.4L, the sensors have an 8 inch wiring. While ordering them, I think there were 13 and 16 inch wires available also, but my originals had 8. Stick with 8 so that you don’t have excess wire to rub over on the exhaust.
9. The new sensor comes with a little bit of anti-seize on the threads. Many people have suggested it is a good idea to add more to the threads. As I said, these were my original O2s with 114k miles and they popped right out. So I don’t think you really need additional, but in the spirit of taking advice I had gotten on the forums here, I added a little bit of additional to the threads.
10. Put the new sensor into the hole on the exhaust and turn it to your left to tighten (it is backwards again). Tighten in by hand, then with the O2 sensor socket and extensions, same as you took them out. Plug in the socket.
11. Next, you want to turn your attention back to the transmission dipstick tube. My wheel-well area was a bit dirty and got some dirt on the part of the tube that goes into the rubber grommet on the tranny. I used a paper towel to wipe this area off really well before guiding the tube back into place above and down behind the exhaust pipe. I then laid on a creeper and rolled under the truck. Hopefully you followed the advice earlier and followed the tube to its entry point into the tranny before you pulled it out so you know exactly where it goes in. If not, you will see just above the exhaust heat shield where the rubber tube going into the tranny is. Wipe the end of the tube off one more time and then guide it into the rubber tube. Replace the bolt that holds the tube to the engine block and put the dipstick back in. Getting the tranny tube back down to this position took a little bit of working it just to get it right into the position down behind the exhaust.
12. Re-install your wheel-well liner and connect the battery.
This job looks far harder than it is. The most difficult part is removing and installing the wheel-well liner. That took me about 20 minutes alone to get removed. If you use the right socket and extensions for the sensor, it comes out pretty quick. I already had my wheel-well liner out when I actually replaced the sensor, so without counting the wheel liner, start to finish on this one sensor was about 20-25 minutes.