No More Security

[VinDiesel]

When I first acquired this '98 K2500 6.5 diesel a couple of weeks ago, a little red light above the light switch kept blinking off and on. Since this is my first car newer than 1988, I assumed this was the security-is-working signal. Tampering with the vehicle set off the alarm almost to a fault; the vehicle "self-locked" after about a minute and electronically locking the vehicle gave a comforting beep. However, the red light stopped blinking at some point and stayed on. Since then, tampering with the vehicle causes no alarm, the vehicle does not "self-lock" and there is no comforting beep when electronically locking. I assume security is no more!
The Security check light on the instrument panel comes on briefly when firing up but does not stay on; I assume this means the system passed some kind of check. There don't seem to be any posts re what I guess is called the PassLock system which is what I assume has a problem. Any help or guidance would be greatly appreciated. P.S. no fuses are blown that I could find. Work done to date: oil & filter change, fuel filter change, side post battery mods made per instructions and Kennedy harness installed.

[jik]

Sounds like somehow you set the alarm into valet mode. Check if there is a hidden switch somewhere under the dash. Next to the new harnes you installed.
Good luck
jik

[diesel65]

The security light by the light switch indicates that you have some form of an alarm system in the truck.
You would need to look under the dash and find the control box then see who the manufacture is so you can get a operators manual.
The security light in the instrument panel is for the Passlock system.
If the light stays on then you have a problem.
If the Passlock detects that someone turned the ignition switch on without a key (no lock cylinder in the steering column), the truck will crank and fire one time but the computer will shut down the injection pump and not allow the engine to run.

[VinDiesel]

Youse guys da men! Thanks to jik for the tip on valet mode because that, with diesel65 making it clear I was mixing up a separate alarm system with PassLock, led to better understanding the keyless system and the un-setting of the somehow setting of valet mode (based on a few clues of the alarm system's vendor site - still need to get an operator's manual). Thanks!