Help with alarm trigger mod

crewl1 · September 11, 2015

I saw that my vehicle build list included something called UTJ-Theft Protection System, Unauthorized Entry and after testing it is just what I was looking for.

(When a door or hood is opened after locking the truck, it chirps then blasts the horn. p2-11 in manual.)

In my previous vehicles I have added a momentary switch inside the door handle so if the vehicle is locked, just a pull on the handle will trigger the alarm, instead of triggering once the door is already opened.

I'm sure this has saved me on numerous occasions because I have returned to my vehicle to find it was triggered but never opened, so I figure the thief got spooked when alarm sounded earlier than expected.

I'd like to do the same for my door and tailgate handles on this truck.

On previous vehicles a switch to short to ground was all I needed, but I don't see door switches and I know nothing about the GM alarm.

Does anyone have info on how the alarm is triggered? Any suggestions on best way to implement my plan? TIA

kchiasson64 · September 11, 2015

Interested

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ikaika1984 · September 11, 2015

I saw that my vehicle build list included something called UTJ-Theft Protection System, Unauthorized Entry and after testing it is just what I was looking for.

(When a door or hood is opened after locking the truck, it chirps then blasts the horn. p2-11 in manual.)

In my previous vehicles I have added a momentary switch inside the door handle so if the vehicle is locked, just a pull on the handle will trigger the alarm, instead of triggering once the door is already opened.

I'm sure this has saved me on numerous occasions because I have returned to my vehicle to find it was triggered but never opened, so I figure the thief got spooked when alarm sounded earlier than expected.

I'd like to do the same for my door and tailgate handles on this truck.

On previous vehicles a switch to short to ground was all I needed, but I don't see door switches and I know nothing about the GM alarm.

Does anyone have info on how the alarm is triggered? Any suggestions on best way to implement my plan? TIA

Found something shoot me a test email...

ikaika1984@gmail

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Mike1220 · September 11, 2015

In for the responses

crewl1 · September 11, 2015

Maybe soon I will do a little exploratory disassembly.

ikaika1984 · September 11, 2015

Maybe soon I will do a little exploratory disassembly.

Sorry email wasn't synch.. Just sent you an email... Hope it helps

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crewl1 · September 11, 2015

No emails received but I will keep an eye out.

crewl1 · September 12, 2015

Tying into the hood switch may be an option if I don't find a way to use door switches.

The hood catch has a set of wires coming to it and it will trigger the alarm when the hood release is popped, so one or a couple of those wires will work.

I'm probably not going to get to this until I pick up the Pop n Lock for the tail gate and I will do it all at the same time so it may be a while.

If anyone wants to get a jump start on their own project the switches that I have used in other vehicles are called Micro Lever Momentary Switches and look like this:

The bottom lug is common and the others are a normally closed and a normally open lug.

For a switch to ground, you would wire the common lug to the alarm trigger input and then wire the normally open lug to a screw on the chassis.

You place the switch lever so that when you pull on a locked handle it pushes the lever against the button on the switch and makes the ground.

These switches have two mounting holes that you can run a zip tie through to position it where needed, or because they are a flat body you can also use good quality double stick mounting tape to place it in the door.

You can also find these with extra long levers that you can bend into the right position to meet with the handle motion.

It might be a while before I get to it but when I do I will document it with pictures for folks to see.

crewl1 · September 12, 2015

In this member's ad you can see the hood cable I refer to above, it is shown in the second picture.

http://www.gm-trucks.com/forums/topic/169005-201415-silverado-sierra-light-bar-mounting-brackets/?do=findComment&comment=1567355

Coming out below the hood latch is a short 8 inch or so cable the goes to a plug nearby.

It sends the signal to trigger the alarm and also shows the hood open in the DIC.

This would be my tie in point for the lever switches barring finding an easier spot in the door.

The cable appears to be accessible by removing the top cover, the whole grille does not have to be removed.

Edited September 12, 2015 by crewl1

ikaika1984 · September 12, 2015

In this member's ad you can see the hood cable I refer to above, it is shown in the second picture.

http://www.gm-trucks.com/forums/topic/169005-201415-silverado-sierra-light-bar-mounting-brackets/?do=findComment&comment=1567355

Coming out below the hood latch is a short 8 inch or so cable the goes to a plug nearby.

It sends the signal to trigger the alarm and also shows the hood open in the DIC.

This would be my tie in point for the lever switches barring finding an easier spot in the door.

The cable appears to be accessible by removing the top cover, the whole grille does not have to be removed.

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This is what I found. Not sure if it'll help.. Or if you already have it...

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crewl1 · September 12, 2015

I don't have, it would really help. The email hasn't come through so I will send you another for you to reply. Thanks

crewl1 · September 13, 2015

I found the doc on line thanks Roger. It was too big to email for sure.

ikaika1984 · September 13, 2015

I found the doc on line thanks Roger. It was too big to email for sure.

Awesome, let me know if it helps.

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crewl1 · September 21, 2015

Today I tried hooking into the hood switch to trigger the alarm from another source but I was not able to get it to work.

The hood latch has a switch that does not connect to ground in either open or closed position, but rather it appears to route a 12v signal via a resistor to the BCM.

I could not get a continuity tone from the switch, only a weak change in resistance when the hood is closed or open.

I spent too much time on this trying to make it work so I'm giving up and instead will see if I can make it work via the door switches.

Seems like I would have to take a course in modern auto electronics.

This was so simple in the old days.

crewl1 · September 24, 2015

So I have determined that this mod will probably no longer be able to done easily using existing factory theft deterrent.

The current door and hood sensors are powered and always sending a signal to the BCM that shows a status.

Disconnecting the switch is recognized by the BCM as a fault condition so the anti theft system will not initiate.

Any approach I might try using a standard open or close type switch will not work into this circuit.

So I am at a stand still. The only possible way to do this might be to duplicate the current sensors at each door and place them so they are triggered by the handle pull. And I can't figure out how that might be connected - series? parallel?

Probably the only way to do it would be to add a second alarm to the vehicle that accepts ground pin type switches.

Since I see no easy way to move forward will have to drop this for now. If anyone has any suggestions please let me know.

Edited September 24, 2015 by crewl1