2000 Cadillac Deville • V8 FWD Automatic • 101,000 miles

Hello gang. I have been trying to get an answer to this problem for about a month now from all over. My 2000 Deville (Base) will not crank. Everything works, battry new, replace key cylinder, crank sensor A & B, ignition switch, starter and starter relay, and check all connections and grounds (to the best of my knowledge). There appears to be a break down between the starter and gound. If you connect a separate ground from body to starter the engine will turn over slowly. If you run the additional ground to the body, it barely turns the engine over I used jumper cables and also tried using on the battery ground. The only codes were P0335, P0340, P0385, which all point to to crank and cam sensor curcuit, all of which seem to have tested fine. Even used a scan tool not a Tech 2 (loaded with updated software, except for the GM high priced subscriptions) a friend has, but could not get a crank request. Any help would greatly be appreciated. I do have the factory service manuals.
December 1, 2010.

Ok hopefully you have checked allth e fuses, etc. There is a crank circuit breaker before the relay that can kick off and not give the relay power. However, there is a yellow wire from the iginiton switch to the pcm it goes to number 6 on the pcm. Then it leaves the pcm at C2 to go to the relay. The ignition switch fuse is in the fuse block under the rear seat. Also clean the battery ground which is under the rear seat by the battery. It could be loose as well.

Dec 1, 2010.
Check engine for good ground
try and run a temp ground wire to the engine metal (you have a lot of a plastic )

Dec 2, 2010.