l am a 71 year old mechanic,my 2003 f-150 boss,had this common problem,many people have spent alot of money on this. over drive light goes on,car won't start,trans not right.bring to ford,they always say it needs cmu,some times it works for a while,not the real correctlon,only needs a new relay,hella brand, did 6 in last 2 years all are still fine,

 

When the OD lite comes on , it usually is due to a problem with the trans or related system. Can you get the code(s) it is setting off ?

When you say won't start, exactly what does that mean? What does it do or not do? As a mechanic I'm sure you understand we need more info.