Hey I have 2015 Ford Mustang GT. For some reason it has started putting itself in Accessory mode while I am driving on the freeway, or anywhere for that matter. It happens randomly and the dealership it not able to replicate it despite repeated attempts. Has anyone ever seen this before?

When it happens the engine essentially cuts off, which is very bad in traffic.

 

So I understand exactly what you mean, are you saying the ignition system switches over to accessory position as if you had the key tumbler/switch moved to accessory instead of on?

Thinking out loud, one way to determine if this is what is happening would be to either connect something to the ign switch to visually see if this is where the drop is originating and see if it is dropping out there or possibly someplace else.
Some equipment is available to record what is taking place and where and possibly your dealer or well equipped shop can connect one to capture the event.

 

That's correct. I get a "Run Power Active" message come up, and I loose the ability to accelerate. I have to pull over, put the car in park and hit the start button to start the engine back up.

 

This could be something like a defective power relay which may be incorporated into an assembly that would require replacement and could be expensive. Nothing compared to getting hit from behind because power was lost. Procedure is usually , duplicate the condition to confirm diagnosis before replacing good parts. If this is a known problem your dealer should have access to service bulletins to confirm this. This is of course a safety item and deserves immediate attention.

 

Agreed. So far however the Dealership has been unable to replicate the issue on 2-3 different attempts. Even keeping the car for several days, which complicates things. The car is still under warranty, do u know if this kind of thing would be covered?

 

I would assume that this is covered under warranty. If you know of a certain time/location when this is prone to happen I would suggest asking the service manager to take a ride with you in hopes that you can trigger the issue with him/her in the car. Our service managers do it all the time in situations like this.

 

Sadly it has happened in different locations at different times and at different speeds. I cannot find a single common factor to any of the times it happened.