Got ICP changed but now what?

I finally got the ICP changed on another thread but the truck would not start. I looked at the ICP on the scan-gauge and saw 4000. Turned the key off and back on and 4000 for about 10 seconds then dropped to zero. After dropping to zero the truck starts right up. If I shut it down after idling for a few minutes with the ICP showing 875 it won't restart. As soon as I turn the key back on it goes to 4000 and won't start. If I wait it drops to zero and starts.

When it is idling normally the gauge show a solid 825. Never saw it fluctuate idling.

Any suggestions?