Horn doesn’t work at all/alarm acting up, also getting boost sensor CEL
 

Hey guys, I was hoping to get some advice about how to figure this out for my 04 speed Miata.

Horn and Alarm
My horn used to work just fine. It would honk when I pressed on it and also when I double-tap the lock button on the fob. That was the only sound that it would make when I locked it with the fob.
Recently, however, the horn makes no sound at all when I press on it, and for the most part, there is no sound when I lock the car. The fob does work – the car locks and unlocks and the lights flash when I do so, but no sound. Occasionally when I open and close the door (and occasionally when I lock it with the fob) I hear a very high pitched beep, as if coming from the alarm itself. For the most part however, there is never any noise. If I press the panic button on the fob, the lights start flashing but there is no noise. What’s weird is that I can still set off the alarm (makes the same high pitched noises as I mentioned before) by shutting the trunk really hard or opening the door when the car is locked. There is a little red LED on my steering column that flashes when the car is locked and responds whenever I use the fob to lock/unlock. I’m not sure if this is aftermarket or stock for MSMs.
I’ve checked all of the fuses and they are all working. I’ve looked into valet mode and that doesn’t seem to be the solution to it. I’ve searched for answers for the last few weeks and I’m starting to run out of ideas. If anyone knows anything that might work, please, let me know.

Check Engine Light
Another issue that it’s been having is that it keeps spitting out the P0106 (Manifold Absolute Pressure) code to me. I bought a new OEM boost sensor and installed it and it worked for a while. In the next few times that I drove it the CEL sure enough came back. I checked the new sensor and it all of the hoses near it and they all seem to be okay. I clear the CEL often now, and it comes back in the next few times that I drive. I haven’t had any issues with performance whatsoever, I just want to know why it keeps giving me this code.


Also, both of my fog lights went out. Checked every single fuse in both fuse boxes and they were all good. Not sure if related at all.

..It’s also possible that this is all just happening because it is so cold recently.

If anyone has any clue about what any of these might be, any help would be appreciated. Thanks!

Check horn itself (they do fail), horn relay (if equipped), or possibly poor grounding of the horn body to the frame.

Check fog light relay, fog light switch, and the bulbs themselves (they don't last forever).

When you say you changed the boost sensor, did you mean the MAP sensor? Check with FM to see if there are any known issues with their kit that may generate that code on occasion.

Yeah, I mean the MAP sensor. That's a good idea, I'll look into any possibilities from FM.

As soon as the weather gets a little warmer I'll take a look. Unfortunately I'm much better with the mechanical aspects than the electrical aspects of cars -- finding grounds and testing electric components isn't my forte. I'll keep this thread updated on how it goes.