Horn goes off/lights when new battery is connected
 

I have an 05 Rx-8 manual. I parked the car about 6 months ago due to life getting in the way I was unable to use the car. The car battery obviously died so I tried to replace it, however, as soon as I connected the new battery the horn went off and the lights turned on (Did not connect the battery incorrectly at all)... I removed the horn fuse to try and see what the issue was but lights in the dash or radio will not turn on when the battery is connected and the key is switched on. I checked the 120v fuse and its fine. I tried to unlock the trunk as some people have recommended but no luck. Any help would be appreciated the car was sitting outside uncovered during its hibernation.

I think the system went into antitheft mode but not sure how to disable it... I changed the battery in the remote as well.

I took the batter in for testing at my local Autozone and they stated it was fine with its 75% power.

You're right, it's the antitheft. When it starts honking use the remote to unlock the car. Even if it's already unlocked, unlock it again.

When you crank the car to turn it on does it start?

Yes, I have tried this already but it will still not turn itself off. I also changed the battery of the remote to make sure that it was not dead... I have locked the car connected the battery and then unlocked it manually but it makes no difference. The remote is not unlocking the car at all.

CaymanRotary, the car will not crank at all. it seems that something is preventing the car from being able to crank.

you could try the key fob reprogramming procedure:


If the key isn’t starting the car that’s a bit of a problem. The immobilizer is active and preventing you from starting the car. Hopeful once you program the fob it should start but I’m not sure.

Thank you! I will give this a shot when I get home tonight. Not sure if this will work while its antitheft mode but I will give it a shot.

You can also lock/unlock the car using the key in the door. That should also deactivate the antitheft.
Close all the doors, connect the battery, it will start yelling, walk around to the driverside door and use the key to unlock it.

Do you have other keys you can use? The key programming procedure needs at least on recognized key to start with. If none of your keys work (after you've disabled the antitheft), you need the dealer to reprogram the whole thing for you.

^ this.

I tried closing all the doors (Locked) and then hooking up the battery but I got no luck...

I was afraid of having the dealership doing it since they are probably going to charge an arm and a leg, but, I guess that will be the price I have to pay. Do you guys know if there is a way to remove the antitheft system so I can at least turn on the car or reprogram the key?

If you don’t want to take it to the dealership you could hire a private automotive locksmith. It’s going to be cheaper but make sure he is familiar with Mazda systems.

edit: there is a chance it could be the immobilizer but I don’t think that’s the problem here. Did you ever check the central locking fuses?

Yes, if the car is locked and the hood is open it will think it is being stolen. Unlocking it with the key in the door doesn't stop the alarm??

The immobilizer is in the ECU, it's not removable.

Alright, so I decided to run through my initial inspections to make sure I did not miss anything. The 120amp fuse was actually freaking blown 🤬!
But now I connected a new one and as soon as I connected it the new one blew... Any ideas what could have caused the new fuse to blow?
The car was parked and ran beforehand so not sure what may be going on. If its a grounding issue please let me know where they would be connected.

Any signs of critters chewing on your wires or generally being around the car? Was the car in a garage or outside?
120amps is a serious fire hazard, so I'd examine the battery cables back from the battery as far as you can. 120 amps would mean something big is shorting straight to ground.
Also I don't understand how anything works (horn, locks, lights) with the 120amp fuse blown. May be wrong, but that's literally the everything fuse.

Yeah I’ve experienced this setting up stereo systems before and it’s always a grounding issue. Hope that helps. Its a fun game finding the grounding issue :)

Well the light will just come and the horn will just go off... but none of the internal electrical will work.

Anyways! Im pretty tied up with life events at the moment. So I will try to work on the 8 in the next couple of weeks. I will come back and update you guys with what ends up happening with the car.

That sounds like what happens when positive and negative are flipped, also. Which is not great.

:wallbash: You were right Loki... I was given the wrong battery at Autozone which had the terminal switched. So that was what was causing the 120amp fuse to blow. I was so mad and felt so stupid when I figured it out. I have spent months trying to figure this out.

When the battery had completely died I had taken it out and one of the terminals connectors looked really messed up so I figured I would just get new ones on my trip to the Autozone. I got there and picked up the "replacement" battery and new terminal connectors. I got home dropped the new battery in and remove the old connectors without paying much attention. I looked at the battery and connected the terminal connectors as indicated on the battery. Which brought me down this long path of hatred for myself.

TLDR: Make sure you have the correct battery for your car.

Forest Park Locksmith are specialized in securing your car. These professional locksmiths are fully equipped with the expertise to handle and provide solutions for all types of lock and key issues.

it's Ok
my friend used to work on cars at night which I knew better not to do
and he installed a new battery and had all sorts of alarm problems
few days later we looked at it in the day time and he left the little plastic caps on the battery terminals and clamped it down

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Did you damage anything other than the 120amp fuse? I just so happen to have connected my battery on wrong like a complete idiot and i hate myself now because i know how to connect a car battery dont ask me where my head was🤦‍♀️ but im freaking out.