You will need a scan tool to access all the typical 6.0L engine no-start data to see what you are missing, particularly ICP volts. I will assume you replaced the ICP sensor and wiring pigtail connector is because your truck was suffering from the infamous uncommanded random increase in engine speed and surging along with the P2285 that happens on 9.5 out of ten 2003 model year trucks. Post up the data when you are able to obtain it.
Thanks for the reply, that's some good advise. My buddy and I just got it running. The whole matter started a couple of weeks ago when the battery light came on. The lights had been surging for a while, but hadn't gotten around to dealing with it. Last week I installed 2 new yellow top Optima's, but still had the problem. Then the surging started, which was complicating the whole thing. I took it to Advanced Auto, figuring I'll make a claim on the alternator I replaced only 1 year ago. They load tested it, and it was dropping just below 13 volts. While it was being tested the engine light finally came on, so I had the guy pull the code (p2285)...what timing
Anyway, replaced the alternator...no more batt light and the lights stopped dimming. The surging however started again a couple of days later. Looking a bit closer and up under I saw the oil on both sides of the block and down the back.
I quickly learned that this wasn't going to be easy, and I'm still trying to justify how poor engineering ends up costing $240 for a sensor and plug, the pain of changing this thing somehow helped me temporarily forget about all of that.
We started from underneath as some have suggested, ended up removing a lot of stuff only to find that the last bolt on the heat shield was somewhere up under the drivers side of the Y pipe...enough was enough, I had had it. I don't remember who's post it was on here that explained how to go at it from the top, by removing the coolant jug and computer...but as far as I'm concerned, that's the route to go. Still not easy, but do-able. Getting the sensor out was one thing, putting it back was another. My Macgyver friend found some wide rubber fuel line that fit snugly over the plug end...with that he was able to fish it back into the dark cave from hell, and got it finger tight. The hose pulled right off and finished w/ some swivels, extensions and a $6 auto zone socket, where we trimmed off a heavy half inch w/ a grinder.
My problem was the previous owner had broken off the clips on the 3 plugs to the computer. I've had the truck for 2 years and can't believe I haven't had a problem before now, guess today was my lucky day. The connectors were slipping just enough not to make full contact. Yesterday I was working alone, but today it took both of us...one to hold the plugs on tight and one to crank it over. Bingo! Nothing a few zip ties couldn't handle! Now she's purrin' like a kitten.