I changed my sensor this weekend and it wasn't as difficult as I had feared. My light had been on for a while, intermittently at first and then most of the time and I had purchased the new sensor some time ago. It is really difficult to get at the sensor. I had put it off because of the difficulty and the potential that it was really a wiring problem. I don't have fat wrists and was still not able to get in past the intake manifold past the alternator.
I removed the air intake tube, but there wasn't enough room to get in through there.
I tried to go under the manifold and I could get my hand in under, but not far enough. What worked for me was to remove the rear plastic clips from the bottom cover, as well as the two clips in the passenger side wheel well, open up the bottom cover and then laying on the ground with my head toward the drivers wheel and my legs toward the passenger wheel, I could pretty easily reach up with my left hand to the sensor. I couldn't see the sensor from there though, so I had to do it by feel, but I could see the wire which helped. Also for visibility, standing looking into the engine compartment, I shined a light under the intake manifold from the alternator side, and was able to see the sensor by looking between the tubes of the intake manifold. From this point on, the procedure I used was:
1. Laying on the ground, reach up and remove the wire from the sensor. I think it was a pinch of the clip to release it, but it could have been lift up on the clip instead.
2. Standing facing the engine compartment, work a 27mm (1 1/16") socket with two short extensions in under the intake manifold .
3. I couldn't get it on the sensor easily, so I laid back down on the ground, reached up and guided it on.
4. Standing back up again, I put a breaker bar onto the socket/extensions combo. I used a breaker bar not because of the torque, but because of flex joint. Then I broke the sensor loose. It came free pretty easily, not rusted on.
5. I laid back down, reached up and unthreaded the old sensor by hand.
6. I had the new sensor ready and right away reached back up and threaded it in by hand. It wasn't difficult at all to get started. The location wasn't too hard to find again because it is round, a little bigger than the sensor.
7. Once it was hand tight, still laying on the ground, I guided the socket back onto the sensor.
8. Standing, I snugged up the sensor with the breaker bar, and removed the socket.
9. Then I laid back down and reached up and put the wire back on until it clicked.
10. Then I put the bottom cover back on, cleaned everything up and I was done.
It was a lot of up and down, but that was better than impossible contortions. The light has been off for a couple days now and I am crossing my fingers that this fixed it