Theft deterrent system problems

[Wascoman63]

I have owned a 2006 Silverado 1500 for a couple of months. Installed a new battery about a month ago. Everything was working fine until I went away for a week. Now the truck will not start - it fires and runs for about 1 second and then shuts off.

I've tried all all of the YouTube video fixes, talked to the local GM dealer, dis-connected and re-connected the battery, put a charger on the battery to make sure that it was fully charged - but nothing has worked.

When I first turn the key to on, the theft deterrent light is not on. When I try to start it the theft deterrent light comes on immediately, the truck fires and them immediately dies.

Sometimes, when I turn the key to the on position without starting the truck, the theft deterrent light comes on for less than a minute, then it goes out. If I try to start the truck the theft deterrent light comes back on and stays on.

The theft deterrent light is either off or on - at no time does it flash.

I'm at my wit's end. Can any one help?

[swathdiver]

There will be fellas along in the morning who know what's wrong.  I've read the posts many times before but my memory fails me.  If you don't see any activity by 0900, give it a bump.

[CamGTP]

Do you have more than 1 key to use?

[richard wysong]

the problem may be with the BCM, MANY recent posts of similar problems but no 1 has posted a fix yet. try disconnecting the battery, turn the key to run, touch the cables together to discharge any capacitors that are still charged then reconnect with the key still on. this worked for me with my friends truck but I think he just got lucky. same year truck and similar symptoms. if and when you figure it out please post what the fix was,

[Wascoman63]

6 hours ago, richard wysong said:

the problem may be with the BCM, MANY recent posts of similar problems but no 1 has posted a fix yet. try disconnecting the battery, turn the key to run, touch the cables together to discharge any capacitors that are still charged then reconnect with the key still on. this worked for me with my friends truck but I think he just got lucky. same year truck and similar symptoms. if and when you figure it out please post what the fix was,

I tried this suggestion today - no luck.  On another forum someone suggested that my ignition key or my ignition key module may be "worn".  Don't know what that means but any opinions are appreciated.

 

Edited July 20, 2022 by Wascoman63

[swathdiver]

We've seen on older trucks the key module get plumb wore out and not work with the theft deterrent system anymore.

 

Do you have access to a Tech-2 or other bi-directional scan tool?  That's the kind of tool that's going to solve this without salvos of the parts cannon being fired.  

 

In Florida by chance?

[Wascoman63]

20 minutes ago, swathdiver said:

We've seen on older trucks the key module get plumb wore out and not work with the theft deterrent system anymore.

 

Do you have access to a Tech-2 or other bi-directional scan tool?  That's the kind of tool that's going to solve this without salvos of the parts cannon being fired.  

 

In Florida by chance?

I am in Oregon.  I do not have a fancy scan tool but my local mechanic does and he has agreed to do a housecall and bring his scan tool along (I buy him breakfast sometimes).  Will let you know what we find.

[swathdiver]

9 minutes ago, Wascoman63 said:

I am in Oregon.  I do not have a fancy scan tool but my local mechanic does and he has agreed to do a housecall and bring his scan tool along (I buy him breakfast sometimes).  Will let you know what we find.

Perfect, just what is needed.

 

@shakenfake Do you remember what the common causes of this is?

[shakenfake]

I would think it is something with the ignition/key or BCM.

One of my first thoughts is turn off VATs with a tune but that is kind of the bandaid solution

[Soonerchevy]

If you take the steering column cover off (carefully its easy to break), there are 3 wires that wrap around the top of the ignition switch and go into a connector.  Pull it, push the pins out and clean the connectors, use a tool to clean the other half of the connector.  

 

I had the exact issues you had, it was hit or miss if I could start the truck or the passlock would engage.  Had to wait 10 mins or so between each try.  Finally got so bad it wouldn't start at all.  I did this about 6 years ago and no issues since.

 

This is a common issue with this gen passlock.  

Edited July 21, 2022 by Soonerchevy

[redvett]

FYI GMT800 trucks have no chip in the key only in the tumbler assembly. Since the truck starts and quits its the VATs system.

How to Reset the Passlock System on GM Cars

Insert your key in the starter, start you car as you usually would and let it stall. Keep the key in the “On” position. …
Wait until the “Theft Sys” light on your dashboard stays on without blinking. This will take approximately 10 to 15 minutes.
Источник: https://gsi-alarme-securite.com/protection-of-life/how-do-you-reset-the-security-system-on-a-chevy-silverado.html

[Wascoman63]

Well, my buddy brought his full-fledged scan tool over.  The scanner kept saying that it could not communicate with the ECU.  Consistently returned a "Class 2 Data Link Malfunction U1000".

 

Our guess is that the issue is not in the computer but somewhere in the bus where all of the communications between the various modules takes place.

 

We checked all of the wires going into the ECU and none are rodent damaged; we check each fuse in both fuse boxes; and we briefly disconnected the Mass Air Sensor to make sure that it wasn't gumming up the works.

 

So, now I think that we know that it isn't the theft deterrent system.  The vehicle will fire and run each and every time you turn the key, but it runs for just an instant before it shuts off.  My mechanic thinks that the reason that it shuts off is that the computer is not receiving any information and therefore it shuts everything down.

 

Don't know where to turn next.

[richard wysong]

the truck I worked on did the same thing, the scanner would power up but not communicate, after trying the remote srart the key wouldn't srart the truck, the blower and the radio wouldn't shut off, no gauges and did the same run for a second, as I said earlier we got lucky that disconnecting the battery fixed it, the problem started when a new battery and starter were installed and fixed itself when I disconnected the bat and went to the parts store for new side terminal bolts, reconnecting the negative terminal I believe the key was on and it sparked a couple times and was back to normal, BCM is the only thing that makes sense to me but I suppose it could be the bus system. I would start by checking the power and grounds to the BCM, good luck and please keep posting your progress, there have been quite a few posts of similar problems but no one n has posted a fix that I have seen

[Wascoman63]

I found some good info on YouTube.

 

"Class 2 Data" refers to GMs network protocol for communication between the various "modules" of the vehicle.  Each module is a dedicated computer that must communicate with every other module (powertrain, body, doors, AC, antilock brakes, etc.).  They are all interconnected by a single wire that shares data between the modules.  This system is set up to operate on 7 volts, so any higher or lower voltage would indicate that one of the modules is failing - or else there is a problem somewhere along the wire.  If any module is dumping the wrong voltage into the system things can go south in a hurry.

 

If you want to know more, I recommend a video by a fellow named "Rico L" that is titled "GM Class 2 Data Line Diagnosis and Repair Info".  He does an excellent job of explaining how this all works.

 

Evidently there is a device under the dash called a "Splice Pack" where wires from all of the modules come together.  They are inter-connected at the splice pack with a device called a "comb".  If you remove the comb you can check the voltage on each of the modules.

 

I haven't done any more yet and probably won't for a few days as I have family visiting.