I have been looking at the wiring diagrams for a 2009 Ram, It's probably the same as yours. The first thing that comes to mind is that the horns are wired directly to the TIPM (connector C3), so the TIPM is commanding the horns on. The door latch switch sense also go directly to the TIPM (connector C7), there should be no relationship between the two. I find that the TIPM and Cluster communicate via the CAN C Bus (connector C1) and that the Cluster module monitors the Horn switch on signal and then tells the TIPM to sound the horn via the CAN C Bus. My guess is that the Cluster is screwed up and telling the TIPM to sound the horn.

I am surprised that the dealer hasn't been able to figure this out. If they monitor the CAN C Bus and the CAN IHS bus while the problem is going on, the bus message to the TIPM from the cluster (CAN IHS (125k))will show the "blow Horn" bit set to either blow or not blow. If the bit is set to blow and the Horn switch input to the cluster is set to not blow, then the cluster is FUBAR. If the message to the TIPM is to not blow and it's blowing then the problem point to the TIPM.

Seems like you have some rookies working on your truck.

EDIT: Looked into the WIN relationship to the door locks and horn

The WIN receives the request from the FOBIK for locking and unlocking the doors, the WIN then communicates to the TIPM and the Door control modules via the CAN C Bus. To the TIPM, it tell it to turn on the headlamps, the park lamps and to chirp the horn, to the door modules it tells them to activate the door locks and windows.

Since the WIN and TIPM and horn switch have been replaced already, it would seem the problem lies in the cluster.

 

Had to go back and look at my repair orders to see if cluster was replaced...which it was....damn!...i thought we were onto something.

 

no wonder they are confused, they've replaced everything! I myself have been going over the schematics for a while and it gets confusing because so much is buried in the multiple buses communicating with each other. Maybe it's time to call it a lemon, I believe the horn is considered a federal safety requirement.

 

I have been down that road too. I bought it used so its not covered under lemon law but is covered under something called the Magnussen Moss act. I have been compensated but still want the issue repaired.

 

On the schematics, can you tell where the dome light and horn come together somewhere? Again, the horn comes on when the domelight comes on and goes off when the domelight goes off. Is there a link online you can send me?