The horn relay is located in the engine compartment, near the battery. It will be a black box with a single wire connected to it.
Step 2: Remove the horn relay
Use a screwdriver to pry the horn relay out of its socket. Be careful not to drop the relay.
Step 3: Cut the wire connected to the horn relay
Use a wire cutter to cut the wire connected to the horn relay. Be sure to cut the wire close to the relay so that there is enough room to splice in a new wire.
Step 4: Splice in a new wire
Use a wire splice connector to connect a new wire to the end of the wire that you cut. The new wire should be long enough to reach the door switch.
Step 5: Connect the new wire to the door switch
Use a wire tap connector to connect the new wire to the door switch. Be sure to connect the wire to the terminal that is activated when the door is open.
Step 6: Test the horn
Close the door and start the engine. The horn should no longer sound when you put the truck in reverse.
Note: This modification will disable the horn completely when the door is open. This may be a safety hazard, so be sure to weigh the risks and benefits before making this modification.
