Hello, my car is an 03 model. I have recently swapped my old battery with another OEM Honda battery. As soon as I connect the new battery, the alarm goes off (but will stop after 20 seconds or so). I did not realize the S2000 does not come with OEM alarm built-in but that it is either aftermarket or dealer-installed until this current issue. Here is my issue now:

1. My key fob is the regular Honda fob. After changing the car battery, it will still unlock the doors/trunk but will not disarm the alarm.
2. Opening the door or trunk will set off the alarm for another 20 seconds or so; the alarm will not respond to the key fob
3. I can start and drive the car no problem. But if I open the door again, it will set off the alarm... even with the engine on. So this leads me to believe the alarm is "independent" of the car itself.
4. Opening the door or trunk with the key will also trip off the alarm.

- I have tried unhooking the battery, letting it sit, reconnecting and no luck. Alarm still goes off.
- I called the Honda dealer and they told me to use the key to lock/unlock the door a few times while the alarm is running. No luck here either. Door closed and opened..
- I even tried reprogramming the fob to the car but didn't work on the alarm

- Since swapping the battery, the alarm LED on my center console now blinks blue and more frequently instead of red.


- I looked under the seat to saw a connection so I unplugged that but alarm still goes off


- I looked under the dash and found a "foreign" Audiovoxx AS-9492 shock sensor strapped in so I pulled the cord there... Alarm still went off. I did not see any other switches besides the sensitivity dial that would allow me to reprogram the alarm


At this point, I am all out of ideas, going deaf from the alarm, and possibly pissing off my neighbors. Can anyone provide any other tips that I could try to do to solve this problem without taking it to the dealer?

I have attached photos to show the wire I disconnected under the seat, the shock sensor, and the LED.

Any help would be greatly appreciated. Thank you!

 

Here's a link to the OEM alarm installation instructions.
It should at least help you figure out if you have the factory accessory alarm or aftermarket, and maybe has other helpful info.
One thing (maybe the only thing) I know is that when the alarm is installed, you substitute a different key fob. Presumably the
original fob would still open the doors, but not control the alarm. Any chance you aren't using the same fob you did before
you replaced the battery?

 

Thanks for that link! I looked through it and then went back to check on my car. I had a bit of hope when I found that "disarm switch" underneath my dash that was the same in the manual. The LED also looks to be the same as well (but in a different spot). I was feeling kinda hopeful that I have the OEM alarm until I reached underneath to feel the driver's seat for the security control unit... but there was nothing down there. I am gonna assume it once had the OEM alarm, then one of the previous owners swapped it for another alarm (as evident by the Audiovox shock sensor), and that was taken out or left in for another one, then the car finally came to me... without the actual remote for said alarm.

When I bought the car, it only came with the two original Honda key fobs and the dealer made no mention of any alarm. And those two were the ones I have been using till this day.

I finally decided to pull out the horn and now there is just the siren going off. I am not having any luck finding the fuse for that though

I called the dealer and they want $100 for a diagnostic... that's a bit hard to swallow for something I can potentially fix myself or the risk of them not finding the cause.

 

You do not have an OEM alarm. What you have is a partially disabled aftermarket alarm. Someone disconnected the ignition disable on it and put it in valet mode. When you disconnected the battery you re-awakened the alarm. Most aftermarket alarms will go off when the battery is reconnected.
You need to go to an aftermarket alarm shop and have them remove the alarm. OR you can just go under the hood and cut the wire to the aftermarket siren.
However, what I would do is assume its an Audiovox alarm and find a dealer who installs them to reconnect it and buy a remote from them. These cars get messed with too often to not have an alarm on the car. Good luck.