For some unknown reason, my security light is staying on all the time now. The car starts, runs and drives just fine, but that light is always on (except when key is off)...

I don't remember seeing it yesterday morning when I came to work, but after work yesterday I did notice it. I started and stopped the engine several times yesterday afternoon too and it came back on each time.

What causes that light to come on, but would still let the car start and run?

 

the resistor on the key may be worn out so the VATS isn't reading it right.

 

Use the "search this forum" for "security light". That should answer most everything.

 

I did that, but all of the posts that I found were discussing issues with the light being on and the car not starting.

I did, however, find the info on your site that explains how to get the codes from the BCM, and plan to try that during my break this morning to see if it will tell me where to look.

 

I know that I have explained many times before on why the light stays on and the car starts. The short version is because a fault was detected after the engine was running.

 

Ok, after digging around some more, I found some of your old posts about this problem.

I may try the resistor to see if the problem is in the switch.

Here are the codes I got from the system: 12, 13, 22, 31, 33, 35, 55 not in that order, but those are the numbers I got.

 

Ok, now I'm even more confused!

I tried a brand new key in the ignition and got the same thing. Car starts and runs, but Security light is solid all the time.

So I measured the resistance of the pellet, bought some 1/2 watt 5% tolerance resistors for that resistance value.

When I got home, I disconnected the connection shown on Shoebox's site for the proper connector, and just for grins attempted to start the car. It started with the cylinder wires disconnected!

So I held the resistor up to the connectors on the VATS side of the connector, and the car still started with the solid Security light.

I thought that it wouldn't start if the wires were disconnected...

Oh, and I pulled the BCM codes again, they were in this order: 12, 55, 22, 31.

 

You should read from the connector under the dash back to the cylinder with the key in it. If the reading does not match, the cylinder or wiring to it is your problem.

If you found it in previous posts, I explained that the system will enable you to start the engine if the trouble occurred after the engine is already running. That means it ignores the key pellet input. That is why it started with it disconnected.

It takes the system a couple of minutes to extinguish the security lamp after proper resistance is seen. So, after trying the resistor bypass, wait a minute or two to see if the light goes out.

 

I don't understand. Does the VATS system remember there was a fault AFTER startup and disable itself so the vehicle will start, until that problem is fixed? What would have happened if I had disconnected the battery a moment, then reconnected and tried to start it? Would it have failed to start?

I neglected to measure the resistance of the wiring with the key in it. So I'll do that as well.

 

Ok. I went back out to the garage and disconnected the wires again. I measured the resistance on the wires in the column with the key in the ignition and received infinite resistance.

I cut the wire and spliced the resistor in to the wire and plugged that back into the VATS module, and started the car. In about the time it took me to put my tools back on my work bench, the Security light cleared and turned off.

I now believe I understand what you were saying about it "remembering" a fault after the car started a prior time, and remaining "disabled" until it read valid resistance.

Thanks!

 

although, if you had disconnecter the batt before fixing the fault, yes, the car would not have started

 

Now, you've got it. The VATS is monitored when the key is ON. The delay in turning off the light after a fault is corrected is probably to keep it from going nuts in the case of a highly intermittent problem.

The "fault enable mode" goes into effect after you have already started your car and then there is a fault detected. The system knows (or thinks) that you started your car with a legitimate key, so it allows you to start the car thereafter (sensing it is a true fault and that you are not a theif). When the security light is on like that, it ignores the input from the key pellet, so your security is somewhat compromised (as with using the resistor bypass).

If it can't read the key pellet on initial startup, then it won't allow you to start the car. In that case it cannot tell the difference from a fault or a theif.

 

Ok, I hate to dig this up but I have a question about LWillman's fix of this security light problem. What exactly was wrong with his VATS system? Was it the cylinder that was acting up? I'm just wondering. My car has been doing to same thing and I know that LWillman fixed his problem, and I am going to try the same thing out on mine. I was just wondering exactly what part of the VATS system he fixed. Thanks,

 

The cylinder where you put the key is where my problem is. It's not reading the resistance of the pellet in the key.

 

Ok, thanks! I was wondering which part failed. Mines been doing the same thing, and I have a spare cylinder from a friends car which he wrecked. But I didn't want to go through all the trouble of getting it all reworked for my car if it wasn't going to work. Thanks!