Will not shift into OD with the 'WAIT TO START" light on
 

i just bought this truck, when you go to start it the wait to start light wont come on, and the transmission wont shift to OD, when the light would come on it would be fine, but the light no longer comes on... well i was tinkering with it today and i noticed the OD switch on the dash doesnt work so i switched the prongs to mate with the cargo light switch... now the wait to start will come on if you hit the OD switch a few times and then go off... as it should, then as soon as it fires up the wait to start light comes back on.... someone please help me as i have to drive this to work tomorrow... thanks from a newbie

Sounds like a PCM issue.

first thing to do is CHECK GROUNDS everywhere. if it hasn't been done beef up the one going from the battery negative to the body, start there and let us know what happens.

also if you want more visibility, post this in the "diesels in distress" forum.