So i did some searching on this site and didnt find what i was really looking for. On my 2000 ls the security light just randomly came on as i was driving down the street. Ive had this since june and its never done it until yesterday, and has since. So far it starts,runs, and drives fine, but im wondering if ill have a problem if i just keep driving it?

 

It likely is the beginning of an ignition switch failure, specifically the passlock sensor. Getting the BCM scanned for codes should produce a code describing the reason for the light being illuminated.

 

getting the bcm scanned, is that a autozone thing or a dealer?

 

It requires an enhanced scan tool not typically found at autoparts stores (GM Tech2, Snap-on MODIS, etc).

 

tech at work scanned it and got a U1064 code, he said thats all he could find.

 

This is what i found on that code:

DTC U1064 Loss of Communications with DIM
Refer to Data Link Connector (DLC) Schematics

Circuit Description
The class 2 serial data line communicates information between modules. Each module connected to the serial data line is assigned a recognition code, or address. This code is used in order to identify which modules are communicating. Modules communicate with each other by periodically sending state of health (SOH) messages. When the ignition switch is in RUN, each module communicating on the serial data line sends a SOH message every 2 seconds. This ensures that the system is operating properly. When the dash integration module (DIM) stops communicating on the class 2 serial data line, the SOH that is normally sent on the serial data line every 2 seconds disappears. The module, which expects to receive that message, detects the absence of the message. The module in turn sets DTC U1064 associated with the loss of SOH of the DIM.

Conditions for Setting the DTC
The module does not receive a state of health (SOH) message back from the DIM. The module retries the request 3 times, and then sets DTC U1064.
This DTC only sets if U1300 or U1301 is not current.
Action Taken When the DTC Sets
DTC U1064 is stored in the module.
The module uses the default values for the initialization data.
This DTC does not cause driver warning message to appear.

Conditions for Clearing the DTC
This DTC clears (status changes from current to history) under any of the following conditions:
The module detects a state of health message from the DIM.
At each ignition cycle.
A history DTC clears after 50 consecutive ignition cycles if the conditions for setting the DTC are no longer present.
Current and history DTCs may be cleared using a scan tool.
Diagnostic Aids
DTC U1064 does not normally represent a failure within the module.
When loss of class 2 serial data communication DTCs (DTCs with the letter U as the prefix) are stored as history DTCs, know all possible serial data DTCs set in each module before diagnosing the serial data line.
If U1064 is stored in the module memory, inspect for the same DTC stored in other modules capable of storing this DTC.
If the DTC is a history DTC, the problem may be intermittent.
Test Description
The numbers below refer to the step numbers on the diagnostic table:

U1064 is the result of loss of communication with the dash integration module (DIM). Note that other modules on the class 2 serial data line may also set U1064 if the DIM is not communicating with the serial data line.

Clear all DTCs after the repair procedure is complete.

Step
Action
Value(s)
Yes
No

1
Did you perform the Data Link Communications Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check - Data Link Communications

2
Use a scan tool in order to attempt the establish communication with the dash integration module (DIM).

Does the scan tool communicate with the DIM?
--
Go to Step 3
Go to Diagnostic System Check - Body Control System in Body Control System.

3
Inspect and repair the class 2 serial data line CKT 1807 (PPL) for intermittent connections. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

Is the repair complete?
--
Go to Step 4
--

4
Turn off the ignition switch.
Reconnect or install any connectors or components that were disconnected or removed.
Turn on the ignition switch.
Clear any DTCs.
Is the repair complete?

EDIT: and here's one from a GM tech......

 

Hubby's 99 Burban had the Security light on... eventually the Passcode system completely failed and cost ME like 2 grand to fix.
I'd take it to a dealer now and see if they can fix it before it fails.

 

i will not pay 2k to fix it lol. and thanks everyone

 

As long as you catch it before it fails and they have to replace the whole security system, plus the starter because your husband burned the old one up, then you shouldn't pay near what I did.

 

I also am having Security light issues with my 2000 Blazer (190Km). I am trying to determine whether I have CTD problem or a Passlock problem or both.
From what I've read the CTD produces a steady Security light and the Passlock produces a flashing Security light. I had both at different times.
Since I'm not the only driver I find it hard to list all the symptons and when they started to occur.
1.-It came to a head recently when the battery got drained while trying to start it.
After charging the battery while it was hooked up it started and worked for a couple of days.

2.Now it starts and won't run. Security light is on and the internal lights are not working, Dome, map courtesy, glove box and vanity.

3.Also drivers UNlock switch doesn't open the door but the close works.

4.The RKE doesn't work. I never used them before but my wife says she used it once in a while and it did work.
I'm planning to check the BCM relays to try and get the lights to work so that the steady Security light may be fixed and then I can check for a flashing Security light problem.
I'd appreciate any suggestions or corrections to my assumptions about the way the Security light works.