MurphDogg

It did go off. You just didn't hear it.

konasmrz

From my experience with upgrading various components in my Tahoe here is what I have learned/ conclusions that I've drawn,that can be attributed to the "does the key in the door lock disarm the alarm" question.

Everything on this vehicle works via datastream communication. As an example, anything and everything electrical located on the drivers door interfaces through the DDS module. This is the block of switches that you would think are simply window/mirror/lock controls. In effectthis modulecontain a microprocessor and flash memory that serves to process analog control signals (window up/down, door lock/unlock, etc) into a digital datastream that is presented to the GM Vehicle LAN. Think of it this way, my service tech told me the Tahoe actually has 25 separate computer modules in it, I don't know if this count is accurate or not, but I know from personal experience that each of the doors has one module, there is the DIC module, BCM module, RKE module, and everything from the radio to the AC controls also are considered modules. All of these modules are attached to this "Local Area Network" inside of your vehicle. If you look at any wiring diagrams you will see a wire labeled something to the effect of "Low Speed GMLAN Serial Data" that goes to every module I've looked at. I'm surmising this is the signal lead for the digital command stream that is presented by each module.

Think of it this way; each module essentially has only two basic common electrical connections: power and LAN interface (also referred to as a BUS). The other electrical connections would be for functions/signals local to the device (e.g., video inputs to the Nav radio, relay connections to electric motors, etc.) All of these modules have a unique identifier (address) and areattached to this data bus "listening" for a command to be presented that carries its unique address. So for example, when you press the passenger window down switch in your drivers door cluster, there is no +12V sent from the drivers door through a physical single wire to the passenger door window motor relay. What actually happens is the Passenger window down switch in the DDS generates a datastream command (PDS address plus window down code) that is presented on the GM LAN and heard by all modules attached to the LAN. However, since the PDS is the only one with a matching address, it is the only module to respond to the command and actually turn on its local relay to power the Passenger window down.

As such, when you turn the key in the lock, it must be electrically connected to the DDS as well which would put out a "lock open" signal on the data bus that the Alarm module must sense and then turn itself on/off.

Days of troubleshooting with a volt meter looking for presence of +12V are over! If you put a meter on a lead and it had some weird value like 6V or was fluctuating, you were probably looking at a data wire. You would need an oscilloscope with a storage function to analyze the datastream. I could really see the risk for problems presented by such an architecture if for example somewhere in the vehicle you had an intermittent short in the GM Lan wire - everything could go wacky (or more likely intermittently simply not respond when a command was issued because the intended recipient module got an incomplete/ corruptedcommand signal, or the signal may have been grounded out)

If and when Helm finally releases the 2007 service manuals I will be able to verify my suspicions. But for the time being I suspect the only method of confirmation would be for ZX1100F1to verify if this description of operationis correct.

As an aside....

I just wonder how long it will be before somebody figures out how to download a virus into the vehicle system over the air from the radio! (and we used to joke about how if Microsoft Windows was an auto manufacturer a daily "crash" would not be tolerated - scary, huh!) Stay away from "fly by wire" steering!

ZX1100F1

Did you possibly forget to lock your Tahoe?
The internal door lock mechanism is designed in such a way to not allow for the use of slim-jim to gain access to the vehicle.
If there was no damage to your vehicle then it is very likely that you failed to lock it.

razor

Normally I would say that it was a possiblity that I didn't lock it, but this time I'm sure it's locked.

My wife and I got back that night after the BSC Championship Game....GO GATORS....and she said "did you lock the car I didn't hear it honk?". If she didn't say that I wouldn't have remembered going back out and making sure the car was locked.

When I found the car the next day, the driver side door was covered in greasy fingerprints. The cops said that the "grease" was used to lubricate the wedge so they could get the slim jim in easier.

I'm not a car theft expert so I assume what their saying is accurate.

As for not hearing the alarm, I may not have heard it by my daughter's bedroom is right there and she didn't wake up. Oh, she 1 and wakes up for anything and everything.

Regardless, it seems that the factory alarm sucks. Any recomendations?

ZX1100F1

From your previous post it sounds as if your vehicle content theft alarm is working properly.

The GMT900's are extremely difficult to jimmy open without damaging the vehicle, while nothing is infallible; it would normally take a key or RKE transmitter to disable the alarm.


Just a side note: these vehicles are equipped with a central unlocking system meaning that; if you use a key to unlock the door you can rotate it (counter-clockwise about 20 degrees) once to unlock the driver's door and then a second time will unlock the other doors.

tj

I usually press my power lock button (on the arm rest) twice as I leave the truck. First push gives 2 chimes and the second will lock all doors and prepare to arm. In 30 seconds, the security light on dash goes out and the alarm will trigger if the door is opened. I tried by rolling down window an pulling up the button.

So it seems you don't need to use the RKE to set the alarm as stated in a previous post. This is an '07 Tahoe.

ZX1100F1

tj,
Is correct, the manual is being updated to read that; the power door lock button and also the ignition key can be used to arm and disarm the vehicle content theft deterrent system.

73shark

Ditto fly-by-wire brakes. I don't even like throttle-by-wire. Just getting old. Sorry about your loss. Now I have to figure out how many different ways one can and cannot set the alarm.

73shark

ZX: Does this mean that if you get out and close the doors and then lock with the RKE, the alarm is not set?

biglg

That is exactly what I want to know. Does a simple lock or double lock and horn honk with the remote and doors closed not activate the alarm?