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Reconnecting Battery Causes Alarm Issue


bullmtnbiker
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I tried the search but couldn't find anything that matches. My parents have a 1999 rx300 with a dead battery (they were gone for 40 days). The battery was disconnected and charged. Now they have an issue. Here is what I know:

a) Reconnect battery

b) Horn blares continuously after reconnect

Tried the following:

*) close hood, close doors, lock/unlock with remote

*) close hood, close doors, lock/unlock with key

*) close hood, close doors, try starting car (key turns but starter does not turn over)

Horn keeps blaring and car won't start. The key does turn in the ignition though. Any ideas?

Thanks in advance.

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Your not the first one to have an alarm issue after a battery disconnect. If you search over at Club Lexus you will get a lot of hits but no real solutions.

My first thought would be to try another battery. Even if you just disconnect the RX battery and run jumper wires from another car for a test.

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Bullmtnbiker, welcome to the LOC :cheers:

This may sound like a silly/obvious question, but are your parents trying to silence the alarm with the remote while the charged battery is connected? Because if they're just disconnecting the battery to get it to stop, the system still remains armed and still thinks the car is being stolen. For future reference be sure that when you disconnect the battery, that the alarm system has been disarmed ie doors are unlocked with remote or key.

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Bullmtnbiker, welcome to the LOC :cheers:

This may sound like a silly/obvious question, but are your parents trying to silence the alarm with the remote while the charged battery is connected? Because if they're just disconnecting the battery to get it to stop, the system still remains armed and still thinks the car is being stolen. For future reference be sure that when you disconnect the battery, that the alarm system has been disarmed ie doors are unlocked with remote or key.

Ah. sorry for not being specific. They left an ES330 and RX300 in the garage when they went on a trip (1.5 months). When they got back, both cars were completely dead. I believe the alarm system was disarmed (i.e. doors unlocked) when he popped the hood to access the battery. He then disconnected the battery and charged it for a day.

The moment he connects the battery, the horn blares. I asked if the lights were flashing, he said the parking lights were on. Not being fortunate enough to own a Lexus (yet), I do not know what the security system looks like when it is going off. He then tried the various things (while I was on the phone hearing the blaring).

Oddly, the ES330 did not have an issue having its battery disconnected and reconnected.

Anyway, if someone knows how to get them back on the road, I'd appreciate it. My dad is 81 and the closest Lexus dealer is 40 miles away so if we could solve this, it would be great.

Thanks.

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From the 1999 RX service manual:

When anti-theft system is set (armed), system locks all

doors, flashes headlights and taillights, and sounds alarm if one of

following conditions occur. See Fig. 1.

* Any door (including back door) or engine hood is forcibly

opened.

* Battery cable is disconnected, and then reconnected.

* System receives panic signal from remote keyless entry

system.

Canceling Anti-Theft System Setting (Alarm Sounding)

When system is set (armed) and alarm is sounding, use one of

following methods to cancel system setting:

* Unlock left or right door with key.

* Unlock doors using remote keyless entry system.

* Insert key into ignition cylinder and turn to ON position.

* Wait about one minute after alarm has sounded. After one

minute, anti-theft system will automatically reset in about 2

seconds if all doors are closed.

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  • 5 years later...

This worked for me after recharging dead battery and the alarm started going off:

1) Disconnect the battery (negative post only)

2) Find your primary key (not valet or spare) and insert it into the ignition (don't turn, just insert)

3) Reconnect negative terminal of the car battery.

4) Take primary key out of ignition.

That should do it.

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  • 1 month later...

Hi , I am a new "old" Lexus owner and new to these forums , and I am sure I am late to this , but I wanted to share my experience. Last night I accidentally left my 2001 RX300 lights on (actually, I'm blaming my mechanic who left the lights in the 'ON' position and I didn't notice that, so I'm guessing that's what kept them on). So the battery was dead in the morning, and being a new Lexus owner , I wasn't familiar with how a Lexus behaves when the battery was dead. (different from other vehicles) . The security light was flashing fast without the key and slowly with the key. I thought mechanic had enabled something I needed to de-activate. It was wasn't at all obvious to me that my battery was dead. I thought my alarm just needed to be deactivated.

So I talked to someone who suggested my battery might be dead and that I try charging it, but as "Bullmtnbiker" mentions, the horn blasted as soon as I connected the negative terminal of the battery to charge. Finally, I just tried connecting it and running into the vehicle to start it, and that stopped the horn blasts immediately and it started and ran fine. I just hooked up to a trickle charge overnight to get the wounded battery back in shape.

So , if your Lexus RX300 battery ever dies, expect the horn to blast when connecting the cables before you can get into the vehicle to start it. Kind of an odd anti-theft setup in my opinion.

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