Had no trailer brakes and no trailer gain and no trailer service warning. On this truck I replaced the sliding module in dash and trailer relay. NO CHANCE. Mine was because someone had bent the the tab on the connection. I bent back now I have trailer brakes. When testing with 12v test light. The brake panel depressed with the test light from ground to blue wire the light will light for a half second. Before test trailer brake blue wire on the truck. Go into the fuse box under the hood. Replace the 30amp square fuse with a circuit breaker 30amp. How to that is get fuse holder and 30amp breaker, put in the fuse in holder. the ends of the fuse holder install insulated female connector. I can make one for you or I send a Pic of mine. private message me for questions.