doors lock when engine is started

Sorry, I don't believe there is a way to disable this feature. You may want to keep and extra key in your wallet or not exit the car while the engine is running.

I have an '07 Trailblazer LT and when I start my engine even if I hit the lock switch on the door panel to lock all the doors the driver door will unlock itself when I shut it. Its suppose to be a safety feature so you wont get locked out. And you can set the doors not to lock at all but it sounds like this isnt working for you so may just be a malfunction with yours.