1994 Chrysler LHS possed horn and automatic trunk release

Tiny
BUBBATIN
  • MEMBER
  • 1994 CHRYSLER LHS
Electrical problem
1994 Chrysler LHS 6 cyl Front Wheel Drive Automatic 110k miles

my 1994 Chrysler LHS is possed! The trunk lid opens by itself, this only happens after it has been setting for a while. I have disconnected the power to it and just use the key to open it. I would like to be able to open it remotely though. Now on to the horn, It's goes off periodicaly for no reason. It eventualy shuts off by itself. Some times it goes off for a short period of time and other times it goes off for a long time. I now know where the fuse is to pull to make it stop, but this is a pain in the butt. It has gone off while driving and while not driving. I have had an electrical guy look at it but he did not have a clue why it goes off. Can someone please help! Thanks.
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Wednesday, May 5th, 2010 AT 7:06 PM

5 Replies

Tiny
CARADIODOC
  • EXPERT
Hi bubbatin. Welcome to the forum. This sounds like it's related to the Body Computer. Does your car have Remote Keyless Entry and the factory-installed anti-theft system?

Caradiodoc
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Wednesday, May 5th, 2010 AT 10:57 PM
Tiny
BUBBATIN
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Yes it does have keyless entry, I am not sure about an alarm system. I havn't used the keyless entry for quite sometime though as the lock on the drivers door has quit working.
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Thursday, May 6th, 2010 AT 12:59 AM
Tiny
CARADIODOC
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Ok, first of all, roll the driver's window down, hop out of the car, use the power lock button on the door to lock the doors, close the door, then wait for at least a minute. The anti-theft system will arm if you have it. Now reach inside and open the door with the inside handle. If the horn starts blowing and some lights start flashing, you have the anti-theft system. This is real important to know when it comes to replacing the Body Computer or the Engine Computer. If you have the anti-theft system, you can use any computer from the salvage yard, but from then on, that computer will only work on another car that also has the anti-theft system. DO NOT borrow a friend's computer if his car doesn't have the anti-theft system.

Both computers have anti-theft programming that can not be undone. If your car does not have the anti-theft system, you must find a used computer from a donor car that also did not have anti-theft, and that can be impossible to find out from the salvage yard since there's no easy way to tell unless the car was running when it was brought in. Even then, they might not have bothered to find out.

When you install either the Body Computer or the Engine Computer with anti-theft programming into your car without anti-theft, the new computer will teach it to the other one. A Body Computer will teach it to the Engine Computer or a replacement Engine Computer will teach it to the Body Computer. At that point the car will not start because both computers are waiting for the disarm signal that's never coming. Both computers will have to be replaced at the same time. If you just replace one of them, it will immediately learn the anti-theft programming from the other one as soon as the ignition switch is turned on.

If you buy a remanufactured Body Computer from the dealer, it will come without the anti-theft programming. It will work in any car as soon as it is installed and will self-program itself for anti-theft only if the system is on the car, when it learns it from the Engine Computer.

I just wanted to get all of that out of the way in case you do need to replace the Body Computer, (Body Control Module) ( BCM).

Is it possible a neighbor has a similar car with a remote key fob? It's rare but not unheard of when the trunk pops open for no reason.

When the horn blows by itself, does it pulse about once per second or does it blow steady? Pulsing is a sign the anti-theft system was activated, but if it stays on steady, suspect a clock spring under the steering wheel that is beginning to break. It is a wound-up ribbon cable that makes a solid electrical connection to the air bag, horn switch, and cruise control switches. Usually those three things will stop working, one by one, but it is possible for the ribbon cable to unravel and the horn circuit grounds out the same as the horn switch would do. If the clock spring is the cause, turning the steering wheel is likely to make the horn turn off.

I've never run into a defective remote trunk switch but given how common it is for plastic parts to warp, you might try unplugging the switch as a test. If the trunk still pops on it's own, at least you'll know it's not due to the switch. Also, try popping the trunk while the transmission is in drive or reverse. I can't remember about cars, but I know on minivans the lift gate will not pop unless it's in park or neutral. If your car is the same way, and the trunk pops on its own while you're driving, that would rule out the switch and would point strongly toward the Body Computer.

Caradiodoc
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Thursday, May 6th, 2010 AT 4:08 AM
Tiny
BUBBATIN
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Thanks for the reply. I tried what you said about the alarm and as I suspected nothing happened so I assume that I do not have a factory anti theft system. I also am fairly sure that the keyless entry was an after market addition. I will try moving the steering wheel the next time the horn goes off to see if it might be the spring you were talking about. When you were talking about the computers it brought to mind last summer when I had numerous check engine lites come on. I took care of two of the codes that it gave. I suspected that it might be something wrong with a computer so I just egnored it for a month or so and it finaly went out and has not come back on. Could all of these promlems I.E. The horn the trunk and the various check engine codes be a failing computer. If so is it wise to get one from a salvage yard? Thanks

Monty Munroe
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Thursday, May 6th, 2010 AT 5:35 PM
Tiny
CARADIODOC
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It's too late now, but when the Check Engine light turns on, there will be at least one diagnostic fault code in the Engine Computer's memory. Those codes provide very valuable information, but once an intermittent problem doesn't occur again, the code will erase automatically after 50 engine starts. Those codes are related to the Engine Computer. Other codes can be set that don't cause the Check Engine light to turn on. When the light does turn on, it means the problem that was detected can have an adverse affect on tail pipe emissions. Even if you want to ignore the light, many auto parts stores have simple code readers that can tell you what the code is for future reference.

The Engine Computer is not involved with the trunk release or horn. It's hard to say if they are two separate problems but both could be related to the Body Computer.

Caradiodoc
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Thursday, May 6th, 2010 AT 11:08 PM

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