Ford Repair Questions? Ask a Mechanic for Answers ASAP
You are correct on thinking the BCM is the problem. The best way to make sure is to tap into the circuit for the drivers side rear turn signal/brake light circuit is to go to the connector at the BCM and tap into the wire coming from the BCM for that circuit and see if power is coming from the BCM on that wire. Below is the circuit and also the connector to look at. It is pin #12 in the connector. Also, if the BCM is the problem, it will need to be replaced and the new one programed to the vehicle properly so it functions properly.
Then the BCM is the problem and will need to be replaced.
Not sure on a good ball park price. I would say roughly about $400. Bu that is just a guess. I do not have access to the parts catalog at home.
Yes, the dealership will have to program it to the vehicle for it to function properly.