alarm, 03 impala

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bumpin96monte

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Joined: August 21, 2009

Posted: August 21, 2009 at 8:02 PM / IP Logged

Hi, I have an 03 Chevy Impala, alarm was installed by a buddy- who has since moved away. For some reason, the alarm would always trip after about 10 minutes, so I quit using it- until I just recently dug into it.

I sat there and watched it, and after just about 10 minutes, the car sounds like it locks itself and the alarm sounds. Now I'm not sure if the locking is coming from the alarm brain because it is sensing an intrusion- and something else is triggering it, or what is going on.

I tried diode isolating the trigger, and still a no go. I tried to switch the negative trigger wire from where he had it run (somewhere up the back of the dash)- and connected it to the floor lamp (comes on when any door opens)- and I get the same thing.

Any ideas?

bumpin96monte

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Joined: August 21, 2009

Posted: August 21, 2009 at 8:05 PM / IP Logged

Oh, btw the alarm is a CrimeGaurd 850i4.

I just tried unplugging the lock/unlock plug- and get the same thing, alarm still goes off after 10 min (but obviously now the locks don't lock)- so something else is causing it.

Chris Luongo

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This member consistently provides reliable information

Joined: May 21, 2002

Location: Massachusetts, United States

Posted: August 21, 2009 at 8:14 PM / IP Logged

https://www.the12volt.com/installbay/forum_posts.asp?tid=102909&KW=uffdog

Read the fifth post down there.

i am an idiot

Platinum - Posts: 13,714

Joined: September 21, 2006

Location: Louisiana, United States

Posted: August 21, 2009 at 8:36 PM / IP Logged

Chris Luongo wrote:

This is a recurring issue on 2000-2005 Impalas, but for some reason none of the companies that write the tech sheets have bothered to add it to their documents.

Not all of the cars do this, just some.

Anyway, yes, after the 20 minutes when the BCM goes to sleep, it puts small, weak pulses on the blue, blue/white, and ORANGE / black door and trunk wires.

The pulses are not strong enough to turn on the car's domelight, but they're strong enough to trigger the alarm and make it false.

To correct this, each trigger must be diode-isolated from the BCM.

DEI has a document on how to do this on Fords....if you can search around here and find it, it's the same idea.

Here are the basic steps:

1. Locate the blue door trigger wire. Cut it in half.

2. Connect a diode inline, to the two halves you cut.

The striped side of the diode should be facing the "car" side (which leads to the latch switch inside the door), and the other side of the diode should be connected to the "BCM" side of the wire you cut.

3. Repeat this same procedure on the other (blue/white) door trigger wire, as well as the trunk trigger wire.

4. Now, the "BCM" side of the diode is still going to have those little pulses, but that's OK because you won't be connecting anything there.

The "car" side of the diode now has a clean, true trigger that won't false.

5. The two diodes you had used on your original install......the ones you used to isolate the car's two door trigger circuits from each other.............now connect each of those to the "car" side of the blue and blue white.

6. Likewise, connect the alarm's trunk trigger wire to the "trunk" side of the diode you placed on the car's trunk trigger wire.

7. Close all doors and trunk, arm system, leave everything untouched for more than 20 minutes.

8. If the alarm didn't false, you got it right, and can go ahead and put the car back together.

Let's Go Brandon Brown. Congratulations on your first Xfinity Series Win. LGBFJB

bumpin96monte

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Joined: August 21, 2009

Posted: August 21, 2009 at 9:41 PM / IP Logged

Jeez, thanks- that helped quite a bit- I definitely wouldn't have figured that one out. I had just narrowed it down to the lock wires setting the alarm off when you posted that, I just couldn't come up with a solution to keep it from setting it off. I'm testing it out right now. Man, its a pain to get to those BCM wires though!

One other quicky- the trunk alarm was never set up. Can I just run a jumper to the trunk light wire to use that as a trigger (obviously with a diode)- or can I pick it up somewhere else?

Thanks again!

mikvot

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Posted: August 21, 2009 at 10:03 PM / IP Logged

This is how I do them. Pull the underdash off. Then you will have the metal knee bolster plate in front of you. Pull the 4 10mm nuts and the multiple 7 mm screws out of that. Once you get that off, look to your left of the steering column...you will see a BIG harness heading towards the fuse box. You can catch your independent door triggers right there. There are multiple wires with the same colors you are looking for, so make sure you test. So much easier to 1076 the wires right there, instead of having to fight with them at the bcm.

bumpin96monte

Member - Posts: 4

Joined: August 21, 2009

Posted: August 22, 2009 at 10:11 AM / IP Logged

"car's trunk trigger wire. "

Everything works great, except the trunk. Anyone know the wire color and location I can tap into to get this?

I ran a wire back to the trunk light- but I can't install a diode back there like up front, or it makes the light not work. Does the trunk switch run all the way up to the BCM separately, then back to the trunk light?

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alarm, 03 impala

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