I have seen this issue many time over on GL1800riders.com. The sensor it self is not hard to get to, it is in behind the front timing cover, it is the connector at the end of the harness that is hard to get to. It is down in the abyss below the shelter, as I recall getting to it is similar to getting to the air filter, but maybe a bit worse, airbag models I am told are the worst one to deal with.
If mine goes bad I am going to add a waterproof connector in to the harness behind the timing cover. probably something like these because of the small form factor.
http://www.cycleterminal.com/jst-jwpf.html
I will also say folks have had their bike's throw that code and it was just a bad battery, it does not take much to spin the GL motor over, but if the battery voltage dips to low when the starter is spinning the electronics for the ignition and fuel injectors will not work and the bike will not start. Have the battery load tested as the first step in troubleshooting.