From what I've read the solenoids are pretty rock solid.... easy way to check or deactivate brakes-

Disconnect plug and line up the 5 flat trailer connector so that the top "blue" trailer wire will plug in to the 2nd pin from the bottom on the vehicle connector (where brown trailer wire usually goes) It has to be on a weird angle, almost 45 degrees, and is tricky to jam in there but you can do it - wish i had a picture. Then turn on your headlights and you now have powered the solenoid and you should be able to back up. If that doesn't work - then there may be issues with the solenoid.