I have a fiesta 2012, on sunday I changed my rear brake bulb ( this is important bear with me) on monday I hit a huge pot hole it was unavoidable at about 60mph, after a while my powertrain warning light came on I lost no power with the car nothing and I drive up and down the motorway. When I turned the ignition off the light stayed off and only came on after I had driven about 8 miles and then again it went off, I've drove the car 2 days straight and the warning lights not come back on, we did plug it in and no error codes came up etc. Tonight driving home my friend who was behind me informed me my break lights were constantly on. When I got home I checked it out and this is what's happening.... when my full headlights are on my break lights are on constantly, when I turn my side lights on my break lights go off and work as they should when I press the pedal but my passenger side light only comes on when I press my break peddle. Now I'm assuming I have done something changing the bulb???? Is this why my warning light came on ?? I'm so confused and have no idea where to start I've had the car a year and have had zero issues with it. When the warning light was on the engine ran as smooth as she does now. 

Sorry for the lengthy message any advice would be really grateful 

Jenny 

First thing you could do is take out the bulb you swapped with another bulb to see if this resolves the issue with the brake light. I can't think of any reason for a powertrain warning to come on for a brake light fault.

It could be that on hitting the pothole there may have been damage done to an electrical cable.

@iantt may be able to offer some assistance (found an old thread here about a powertrain warning light but no update as to what was the problem unfortunately). 

 

Is brake light/ tail lamp a double filament bulb? A good chance the bulb is not in right and the two terminals at bottom of socket are bridged by the solder pads on bottom of bulb.   Or faulty earth (negative part of circuit) on rear light.