Security Light 1997 Lesabre

I have a "Security" light on constantly as of this morning. Does anyone know what sets this off? Thanks.

Does the car start up normal, when the light stays on?
Chris.

Yes. It starts and runs great as always. It has just under 215,000 miles on it. I may try disconnecting the battery.

Sounds like the VATS (Vehicle Anti-Theft System).
If the resistor pellet in your ign key is not detected by the VATS (wiring problem most likely), it will disable your starter and fuel systems. So, when you turn the key, nothing happens- it won't even try to start.
I had a 1992 LeSabre that would do this at times, but not always.


There are 3 things you can do here to remedy the problem:

1. Replace faulty VATS component(s).
A dealership's answer that will certainly work. Costs several hundred at a GM dealership.

2. Bypass
A resistor (of correct value) can be installed in the wiring going to your ign switch. However, this will defeat the VATS, making theft easier.

3. Temporary fix
Turn the key to RUN, and wait for the SECURITY light to go out. This will take about 3 minutes (some suggest you wait 5 or 10 minutes). Turn the key to OFF, then start the car. The light may come on again, and stay on while driving to indicate the problem. This will at least allow you to operate the car.


Because it's electronic, and you noticed the problem while operating the vehicle, it's very likely to have come up as an intermittent problem. You may never have a problem starting it... it could fail to start tomorrow.

Keep the temporary fix in mind, or write it down and stick it in your glovebox. If the system does start acting up, you won't be stranded. If it becomes a recurring hassle, go for the bypass or repair.

This is great information. I like option 2, bypass by installing a resistor of a correct value. I will take a look at the wiring diagrams later today. Do you know which wire needs the resistor and what the ohms should be? Resistors are fairly cheap at Radio Shack. Can the wire be accessed under the hood, near the computer? Thanks.

I have a "Security" light on constantly as of this morning. Does anyone know what sets this off? Thanks.

Does your car have a theft and tampering security system? I don't have that on my Limited 98, but does it use the same Security light as the VATS system uses upon starting?

I have read some people suggesting a Security light on Bonnevilles is sometimes caused by a problem with the tamper sensor on the trunk. They suggest disconnecting it to see if the light quits.

The VATS system turns on the light for about 5 seconds as the key is turned to ON. Then the light goes out if the resistances are correct that it reads. If not the security light blinks for 3 minutes and the Theft Deterrent Module (TDM) resets for another reading upon key insert. If it gets the right reading that time, the VATS sends signal to the computer and injectors are turned on and the start relay is activated.

If the TDM does not get the right reading it has two failure modes which I believe both won't allow the car to start. A third mode for failure is where the TDM determines it may not be reading the resistance correctly and defaults, allowing normal car operation sans any theft resistance via key copies without the right resistance.

The light coming on and going off while driving may indicate the latter is happening. The resistance in the thin threads of the wires where the steering column tilts changes while driving, e.g., and the module finds the resistance outside the approximate 10% errors from when it was first started with that key at the factory. I have read of a couple of people who cut the wires while the car was running to put the TDM into that failure mode hoping to live happily ever after. I don't know if they eventually had trouble or not.

My car started giving occasional no reads and read okay on reinsert key immediately. Once in a while it would take 3 minutes. The light would go on and off while driving. Now I get no security light at all. It's been about two years.

I see nothing in the factory service manual to indicate leaving the key ON and waiting 3 minutes will allow the car to bypass the TDM requirements. In fact, after the 3 minutes expires, the TDM reads the key again. Bad reading = no start.

The contacts in the lock cylinder that brush the key resistor can wear or get dirty along with the resistors. You might try cleaning those with alcohol and the resistor chips can be cleaned with a rubber pencil erase that's just abrasive enough to clean it. Other than that, if it really is your VATS instead of tamper security, you're due for a resistor replacement to bypass the reading up in the steering column.

Do you know which wire needs the resistor and what the ohms should be? Resistors are fairly cheap at Radio Shack. Can the wire be accessed under the hood, near the computer? Thanks.
I believe there are two small white wires running up the steering column to your key-switch. They seem to have a tendency to get damaged/worn (tilt steering, etc.).

You will have to use an ohmmeter to measure the resistance on your current key (if your key isn't the problem). It should be close to one of the following values:

1 402
2 523
3 681
4 887
5 1130
6 1407
7 1870
8 2370
9 3010
10 3740
11 4750
12 6040
13 7500
14 9530
15 11800

Imidazol97 knows more about these systems than I do, but I can verify the "waiting for the SECURITY light to go out" thing has worked for me on multiple vehicles with VATS.

if you realy want to do the bypass go to youtube and type in gm bypass there is a real good video on it i did my 97 bonniville with the help of that.

Imidazol97 knows more about these systems than I do, but I can verify the "waiting for the SECURITY light to go out" thing has worked for me on multiple vehicles with VATS.

Smith1000 has not replied to my question as to whether the car has a tamper/theft alarm on the body.

I purposely ordered my car without that in 1997 because I had heard people with some problems call in on radio mechanic's repair shows. I hope he doesn't have a tamper alarm problem and instead is chasing a VATS problem. However the VATS problems are fairly general.

I would suspect the second time after waiting three minutes the TDM read the right resistance from the key through the breaking strands of wire in the steering column. The service manual doesn't say that waiting one 3-minute cycle would allow the key to be used. That negates the whole purpose of the VATS which is to delay the theft by requiring 3-minute waits between testing each of the different 15 resistances. Most thieves don't want to wait around an average of 21 minutes guessing they'd hit the right one. There are resistance boxes that have the 15 resistances and you just switch between them until the find the right one, all with a correct key copy in the ignition to turn the cylinder or with the column damaged to move the rod to the ignition switch with turning the lock cylinder at the top.

The car doesn't have a tamper/theft alarm on the body, so it must be the VATS problem. It is still starting and running fine. I may try cleaning the key with an eraser and the ignition switch. Sounds like it is due for a resistor replacement. I'll check out the You Tube video as well.

I cleaned the key and there was no change. Tried the other key and the light is still on, regardless of the key. Measured the resistance and it appears to be in the range of 500-600 ohms. I do not have a working digital volt meter at the moment, but used an analog. Measured the other key and both keys measure the same, so the keys check out okay.

The light comes on at start up, never blinks and stays on constantly.

Evidently you security system is stuck in what GM refers to as “fail-enable mode”. This happens when a key recognition circuit failure occurs with the proper key in the lock and usually due to frayed wires leading from the key recognition circuit, or momentary loss of battery power while driving. Essentially, the theft-deterrent system goes ‘off-line’ and the engine will start and run with any key that turns the lock. The security light will remain ON everytime you start your engine, after either event mentioned takes place. If you do not correct the initial problem, the same problem may return. Your security system can be reprogrammed using a Tech-II scan tool, or you can try the reprogram procedure below.

Here is a 30-minute programming procedure that does not require a scan tool.

1.Turn the ignition switch to START, then release it to the ON position (the engine will not start).

2. The “Security” light should be ON. After 10 minutes, it should turn OFF.

3..Turn the ignition switch OFF and after five seconds, repeat steps 1 and 2.

When this procedure has been followed three times, turn the ignition switch OFF. The control units will exchange the correct commands during the next start-up attempt. If the programming is not completed correctly, there will be no theft protection or the system will lock in antitheft mode and the engine will not start. Try the programming procedure again. Note this procedure will not reprogram the key recognition, only the information transmitted on the Class 2 data link.

Could it be left as is in "fail-enable mode" indefinitely? I watched the You Tube video and it is very good. The VATs bypass would be a quick fix otherwise. I am not concerned about having a security system on the car at this point, but would rather avoid a no start situation.

If you disconnect the battery, or the battery should lose power, the system my default to active mode when you restore full battery power, which means; the car will not start unless the key resistance is recognized and the communication between the TDM/BCM is complete. As long as you maintain 12v+ voltage, you can continue to drive it with the light ON.