Cadillac Repair: Cadillac wont start, possible starter, engine cranks, starter relay

Question
I have a 1999 Deville and it won't start, when I turn it over it clicks once, I replaced the battery it was dead, and now brand new battery.  I want to make sure it is the starter or see if it's possible it could be the ignition switch or something, lights have flickered a little when driving.  No engine codes, had a P0171 I have changed all plugs and wires and all the coils recently, the alternator is new.  It is due for an oil change now.

Answer
Try jumping the starter at the starter relay behind the glove box. If the engine cranks over and or runs for 2 seconds and shuts off, Your problem is most likely a faulty PASS-KEY system.

If you are mechanicaly inclined or know of someone who is, You will need a DIGITAL MULTIMETER, Simple electrical schematics, Test procedures and picture locations of the components within the system that is causing you problems of which can't be done on this website which only allows one picture. I do not have a website so you will have to e-mail: onlineautohelp@msn.com in order to obtain the information.