the battery to my2005 mercury mountaineer was taken out and checked for about 3 hours when it was put back into the truck it would not start and a message came on that said failsafe mode, how do we get the failsafe mode off?
This can happen when the battery is disconnected and the throttle body has carbon build up. The PCM tries to relearn idle settings and the throttle plate sticks from the carbon. The PCM sees the APP (accelerator pedal) position and tries to open the throttle plate to a specific opening and cannot. Many times this can be fixed with a good throttle body cleaning. I use throttle spray cleaner and a soft pipe brush. , you can do this after you remove it or on the vehicle. Remove the air inlet hose and open the throttle plate with you fingers, spray and clean.
Always good to know if we have any stored trouble codes if you can get the vehicle scanned for codes.
lets start here
yhanks ironmike that fixed the problem and my truck is now running
good for you. great job.