I've got a 98 DeVille. It goes 2-3 days starts and runs fine, then i go to start it and nothing at all. when I hook up the jump box sometimes the interior lights come on, thetrunk pops open and the doors unlock. But every time that I jump it the car starts right up. I have noticed that when I turn the car off that the display for P R N D L stays on and that is when it seems to not want to start. The car runs great other than this problem. Any help would be appreciated.

 

Check the POS battery terminal for corrosion.
That red rubber boot slides off to expose the terminal end.
Sometimes that whole POS cable needs to be replaced.

Other than that, a bad battery or loose connection is all that comes to mind.

Hope this helps.

 

perhaps unplugging the neg battery cable overnight to reset the comp.?