2005 Impala door trigger diode isolation

Hello everybody!  First of all I want to say thanks for the wealth of information on this site.  You all really know your stuff.  Okay, here's my problem:  I recently installed a Viper 791xv in my '05 Impala.  I followed all of the diagrams, and everything worked flawlessly from the first test aside from one problem.  I diode isolated the two door trigger wires and the trunk pin from themselves and the BCM following the 1076 document and tied them all into the (-) door trigger input on the alarm.  However, I recently discovered that when the trunk is open, the display on the instrument cluster flashes between "Door Ajar" and "Trunk Open" and the interior lights are on.  Only the driver's door lights up the interior lights and causes the "key in ignition" chime, which is correct I assume.  Also, only the driver's door, the rear passenger door, and the trunk trigger the alarm from what I can tell.  This is very confusing.  Could some of the diodes have been defective or damaged?  I used the 1 amp diodes from RadioShack.  Thanks for the help!

~Randy

P.S.- If anyone needs wiring / mounting / diagram help for the 00-05 Impala / Monte Carlo, let me know.

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There are 10 kinds of people in the world... those that understand binary, and those that don't.

I doubt the diodes are defective.

The correct wires are in a pink plug at the BCM near driver's kick.
The LF door is gray/black in pin 10.
The RF door is tan/white in pin 8.
The LR door is lt. blue/black in pin 15.
The RR door is lt. GREEN/ black in pin 14.

I would disconnect all then try each input one at a time, then when I'm sure they work individually, connect them one at a time until the problem re-appears (if it re-appears).


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Prepare your future. It wasn't the lack of stones that killed the stone age.

Thanks for the reply!  I used the dark blue and dark blue / white wires in the gray 16 pin plug at the BCM ( per https://lund-industries.com/Wiring_Info_Files/WIRING%20INFO-2005%20Impala.html).  I then used the RED / black wire in the gray 24 pin plug for the trunk trigger.  All three of these should be diode isolated like in the DirectFax 1076 document (cathodes tied together, anode facing BCM and alarm).  Supposedly the dark blue wire catches the driver's door and the dark blue / white catches the others.  That doesn't make sense though, since only one or two of the passenger doors is triggering and the trunk is obviously tied in with a door somewhere.  Anybody else have any ideas?

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There are 10 kinds of people in the world... those that understand binary, and those that don't.

Reviewing the Schematics in Mitchell I say that I agree with you 100% for the wires you've chosen.

LF is Blue C3/A8, (-), Door open.

RF, LR and RR is dark blue/white C3/A1, (-), Door ajar.

Trunk is RED / black C2/A11 (-)

C2 is large gray plug

C3 is small gray plug

These wires go straight from the switches to the BCM.

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Prepare your future. It wasn't the lack of stones that killed the stone age.

Any idea what could have went wrong?  I figured maybe I could have overheated a diode when I was soldering it to get the trunk to "un-isolate", but that doesn't explain why only some of the passenger doors trigger.  I wonder if there's any problems with the door pins in these cars? 

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There are 10 kinds of people in the world... those that understand binary, and those that don't.

Just a silly question, are you connecting doors to the green wire and the trunk to the dark blue of the 791?

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Prepare your future. It wasn't the lack of stones that killed the stone age.

No... It's a negative trigger, too.  I'm just treating it like the two door inputs.  So the dark blue, dark blue / white, and red / black (trunk) wires all go to the green door trigger input after being diode isolated.  What dark blue input are you talking about, the multistage input?   Thanks for the reply! 

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There are 10 kinds of people in the world... those that understand binary, and those that don't.

The trunk trigger wire should go to the H1/6 dark blue wire on the main harness of the 791. It's a dedicated trunk input.

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Prepare your future. It wasn't the lack of stones that killed the stone age.

Now that's somewhat sneaky on Directed's part.  If I look in the installation manual at the wiring info, it says that's a multiplexed input for the second shock sensor.  If I look on the back page at the wiring diagram, it shows that as the trunk trigger.  I just found another post on here with the same problem.  Looks like I have to take my kick panel apart again after all, cuz I'd like it to show the trunk input on the remote.  Hope I didn't cut that wire too short!  lol   Anything else you can think of?   Thanks!

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There are 10 kinds of people in the world... those that understand binary, and those that don't.

05impalaman wrote:

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. . . Anything else you can think of?   Thanks!

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1) Impala's have OEM anti-grind and connecting a tach wire could be counterproductive. Program the 791 for "Voltage sense" and "Voltage sense LOW" and "2 second crank".

2) You must connect the brown acc wire at the ign switch and be sure to feed it as an acc (not ign) or she'll never start.

3)Diode isolate the white parklight wire so there is no feedback to the switch.

Better still, use the blue negative parklight signal ( bcm, gray 16 pin plug, pin a2). No relay required for the latter but be sure 791 is set for negative output.

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Prepare your future. It wasn't the lack of stones that killed the stone age.

Cool...

1.) The tach was easy enough to get to.  I guess it would have been easier to do the voltage sense, but at least I can be sure it's not going to over-crank  lol

2.) Yep, I connected that using the second accessory output and a relay.  Good thing I did.

3.)  I just used the relay option on the white wire, that way I could be sure I had enough current at the same time. 

I guess I'll just switch that trunk wire over and try to figure out why all of the doors aren't triggering while I'm down there.  That will at least fix the "Trunk Open" / "Door Ajar" issue.  Thanks for your help, Big Dog! 

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There are 10 kinds of people in the world... those that understand binary, and those that don't.

give 'n take . . . .it's what it's all about.

I'm a die-hard fan of this site and promote at every opportunity.

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Prepare your future. It wasn't the lack of stones that killed the stone age.

Ok... I finally got around to fixing this.  Apparently it was the diodes on the wire for the passenger doors.  I couldn't get continuity to ground with the passenger doors open on that wire unless I took out the diodes.  I replaced both of them and hooked everything back up.  Now it all works perfectly.  I didn't get a chance to find the blue trunk wire and move it over, but I'll do that eventually.  Lesson learned:  check diodes before installation, and be extra careful when soldering them together.  Thanks again for the help! 

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There are 10 kinds of people in the world... those that understand binary, and those that don't.

Glad it works.

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Prepare your future. It wasn't the lack of stones that killed the stone age.