It IS fun to get to..... I pulled the air filter housing, laid a piece of plywood from the radiator support to the engine, and laid myself on that, so I could reach down in there, and be at least kinda comfortable...... Still, I didn't get some scratches and cuts from the job.

 

I reached my arm through that little hole behind the passenger wheel and the firewall/mudguard by the end of the header. My arm looks like I was using it to fend off a wolverine, or possibly mixing a bathtub full of glass.

 

If it was me .... I saw it on the internet so it must be the right way ...

I saw a video where the guy cut a access hole in the firewall/floor to get to it, from inside the cab. Cut in the right place and it was very easy to get to it.
In fairness the truck was a old rusted out snow plow truck he bought cheap because it did not run and needed a bunch of work ... He was going to park it at his lakeside cabin where family spent winter holidays and only plow his driveway and never go on the highway again ... so he did not care about it.

To be honest, it would be so easy to use some speed nuts and bend up a metal cover with some weather stripping for a seal .... make a professional looking access cover for it. Then the next time you can easily get to it.
I feel the factory should have put a cover there ... that would cost $1 more per vehicle. .... In the end you will throw your carpet back over it and never see it again ... unless the sensor goes out and then it's no big deal.

 

I thought about that method, but, nope. too tight, arm didn't fit, and couldn't see what I was doing. Going from underneath was too much of a reach, and bending so I COULD reach was incredibly uncomfortable. So, in from the top.

I am just not a fan of carving holes in my truck to access a part I might change ONCE during the course of my ownership.

 

Thats fair. I have made access panels on 3 different vehicles so far, I do not regret it at all. One time on a Ford explorer, if I was caught working on my vehicle in the apartment parking lot ... I would have been kicked out.
I lifted up the rear seat and cut a hole in the floor to replace the fuel pump ... I kept the vacuum cleaner out there and used tin snips for the hole .... the manager just thought I was doing a interior cleaning.

I did not cut this one, previous owners did it ... I'm just glad they saved the pieces and was able to weld 3 pieces back together and put it back in .... they really did a hack job cutting it out.
So it was difficult to straighten the pieces, weld them back together, then try to align the body lines ....
This GM truck has 430K miles on it and more then 1 fuel pump .... GM greater ideas is to remove the bed and raise it up to change fuel pump.



Not proud of it, wish I cut it open knowing I would have to put it back in .... After a couple years, you hardly notice it unless you are looking for it. .... Just showing a example of cutting the body and making a panel.
Anyone can do a better job then this, if you think about the job from start to finish, before just going in and start ripping and tearing like the previous owner did on this one.

 

I am of the firm belief that the engineers/designers CONSPIRE to make some parts of the vehicle incredibly difficult to work on....... On some GM front wheel driver cars I had the misfortune to work on, you had to drop the engine cradle to change a water pump, because ONE bolt didn't have enough room to be removed.......