crwiseman

I replaced a dead battery today, when I connected the negative cable (after the positive), the horn starts blowing non-stop? I previously replaced the battery a month ago (new battery wouldn't hold it's charge) and I did not have this problem.

Before I changed the main battery today I replaced the key fob battery figuring that this is why my doors would not unlock and then I realized the main battery was the culprit.

Any clues???

TrevorR

iTrader: (2)

crwiseman

TrevorR: Thanks for the response. I doubt that I reversed polarity initially as I have been wrenching for like 45 years and have never made that mistake. if I DID make that mistake , what fuse are you talking about?

mr2dave

Did you try starting the car with the horn blaring? Try that or hit your fob lock/unlock buttons.

crwiseman

OK, after much trial and error, this method works perfectly if your battery dies and your Lexus locks down thinking you're are trying to steal it:

If it's a factory alarm, exit the vehicle and close all doors then lock the vehicle with the key from the driver's door key slot. Attach the battery leads and then unlock the driver's manually with key and the alarm turns off instantly. Taa Daa!

Htony

Isn't there a horn relay? Pr0bably it is stuck closed or something wrong.

crwiseman

No, the car is hard programmed to think after losing all power that someone is trying to steal it after restoring power, hence the blaring horns. You need to lock it then unlock it with the hard key to let it know it's not a thief. You "can" drop the car horn fuse under the hood (I tried) but the other alarm horn keeps going because that fuse is in the trunk which you can't get to because the trunk is locked . . . electronically.

jonez

crwiseman

The first time, the battery was just too weak to start the car and was only out during the swap like 15 minutes. The second time, the battery was completely dead, no warning lights, no nothing. Plus, the battery was out of the car for several hours as O'Reilly Auto insisted "testing" the dead battery for over an hour.

TrevorR

iTrader: (2)

Sorry, I speak from personal experience, you definitely have more wrenching experience (No sarcasm). I was replacing the battery and was completely oblivious to which terminal I was attaching. I put the wrong terminal on for a split second and some sparks went off. I put them on correctly and the horns started blaring continuously. Battery was new and tested good but I checked the fuses one by one and a three of them were blown.

One was the anti theft system fuse. Can't remember the other 2. I'd suggest starting to look at fuses. It seems weird but that was my experience.

Edit: looks like you solved it, ignore my post!

youdakine

I'm reaffirming this method. On my 2008 RX400h, my starter battery died from lack of use and after a battery check and recharge at Advance Auto, decided to replace it with one from Costco. Easy install with my 10mm ratchet wrench and 10mm socket. I closed all the doors, attached the negative terminal last, the horn blared, unlocked the driver's door with my key and the alarm became silent. Nice! Next, the windows reset instructions that I found on YTube. The window switch for each door had a blinking light and on each door, rolled the window down, held the button down for 4 sec then raised the window up, held the button up for 4 sec. This, so all the windows could then be operated from the driver's door. Then made sure the sunroof operated. Then I tried the fob hold down unlock button and yay(!) all the windows open together. Then the radio and then the driver's seat reset. Everything good.

Vilmi

Hi there!

I had someone made that mistake when replacing my battery and now my car is completely dead. Ive watch a million videos trying to figure out which fuse got blown (hoping thats what happened ) and i came accross this forum. Can any of you guys please help me locate the fuse that mighthave been blown, im assuming is the one related to the engine or battery? I did some reasing on the owners maual and took out the two fuses i found to look like they were blown. Please help!!!!!

GSFbeast

Here's my thought about replacing the battery. TAKE IT TO THE DEALER. There's a lot of $h!t going with these Lexus cars, I don't know what. Some of them are bad idea to mess with. Yeah it's as simple as a battery replacement. $h!t could go bad real quick. I took the battery off of my GX and installed it onto a dead car. All worked fine, but when I put the battery back into the GX. The Nav system took a big dump. Pitch black. Since there's very limited physical buttons for the climate control. It's was a nightmare when the screen goes out. The stealership wanted to charged me $10K for the unit. I swore to never buy a Lexus again after that. Since I took the battery out myself they blamed the whole thing on me. I took it to another dealership and they replaced it for free under warranty. As reliable as everyone's are saying about Lexus cars. I'm having a second thought on that. The only thing I would do on my Lexuses are: Oil change, Tires rotation and minor lubrications fill-ups that's it. Yeah, I'm scared to touch that battery. It's bad juju.

lobuxracer

iTrader: (2)

I've had a bunch of batteries in my IS F and never had a problem. The GS F just got an Antigravity battery and won't need a new one for a ridiculously long time, but the AG is the third battery in the car. Never any problems, but I've definitely heard of problems. One of the worst things you can do to these cars is let the battery go low (sub 10v). That kills lots of expensive things.

CytoRager

Fuseable link fried along with 5 other larger fuses 60amp... In my case also fried main nav/radio/AC unit and because Pioneer wont accept core $3,500 replacement is over $26,000 ! ! ! Yes, American dollars.