Freightliner starts and immediately dies

Freightliner Columbia with Mercedes engine. Died while driving, restarted but dies within seconds, so I unplugged the oil sensor and it ran with check engine light a few miles and same thing. Next day I couldn’t find anything wrong but did notice it ran with the key in the start position but as soon as you let go, it dies. Changed the cam and crank sensor now it dies after a few seconds again. Oh and I did put a new ignition switch as well. Something electrical but can’t find it