When i bought my escape from the ford dealership, they had a deal where they would put on a new auto starter for me. However, on and off it interferes with my cars' ability to recognize the 'unlock' on the keyfob, and so doesn't turn off the passive antitheft. In short, the vechicle will not start if the antitheft does not disengage. It only happens for a few hours at a time, but at first it was enough to really worry me.

I had my vechicle towed (under warranty) back to the dealership the first time it happened and the ford 800 number didn't know what the problem was, and by the time it got there, the unlock worked again. This unlock shenanigans happened a few times, until i finally got sick of it and took it to a Ford Special Vechicles group to have it taken off... only to be told by the service manager that there was an override button hidden under the dash that would disable the auto starter, and allow the passive antitheft engine cutoff to be bypassed. I think i dropped the F word several times.

The auto starter also made it so that if i just want to use the key to unlock the door and start the car (and not the fob), i have to press the override button first. With the auto starter, i otherwise have to press the unlock on the fob to start the car normally.

The long and the short -- if you get one put on, get them to show you where the override is just in case something goes wahonnie shaped. There will be an override somewhere, and the installer should know where it is.