2004 Mazda 3 S horn issues
 

Hey guys new to the forum and Mazda 3s! I have a 04 Mazda 3 S hatch 5-speed manual I got cheap, Kid thought it had a blown head gasket cause it kept running hot, turns out it was just a thermostat, replaced it and no overheating issues now. Fixed all the drivetrain issues it had mostly just routine maintenance Spark plugs, air filter valve cover gasket, and coolant flush. Well, Today was the first time driving it any distance it did great until I got to work. I pulled out the key fob and hit the lock button once..and the horn wouldn't stop blowing I pulled the relay to make it stop I worked all day and then got home and did some troubleshooting. Swapped several of the relays and it just won't stop blowing (fixed a non-working AC issue in the process always fun to fix something while trying to troubleshoot something else.) The horn worked fine before I used the key fob and I noticed that now the Key fob won't work at all. But I did lock it several times while it sat at the house waiting on the title to come back so I could register it. Does anyone have any diagrams they could point me at? Does it also run through the fuse box under the Glovebox? I'll have to replace that sooner or later as I do have to slap it to get the running lights to work some time and am aware of that issue with it. I pulled the Alarm fuse but that didn't help either. Any suggestions would be appreciated.

Well after doing some research I find that the Horn circuit runs through the PJB and there have been a handful of cases that a bad one could cause the horn to get stuck on. I already planned on replacing it because of the running lights issue and have pulled the part number off of it and will post the results once I've changed it. Any word on whether or not this has to be programmed or not? I hear a lot of yes and no about...or is it a case by case type deal?

Status update! Well, it took me a while but I managed to find a PJB with the correct part numbers on it and just finished putting it on. I didn't have to have it programmed was plug and play, now all my running lights work properly as well as my horn. I saw signs of water intrusion in my old PJB and decided to open it up and found water damage on the board. The kid did tell me that he had left the windows down on during a few heavy rainstorms and I had replaced the carpet and seats because of that -they were super nasty-