"Security" light is lit.

mjmsprt40 · Aug 19, 2015

OK... I've had this problem off and on for some time, right now I want a handle on how big a problem this is.

The "security" light illuminates on my dashboard while driving. At the moment it doesn't seem to cause anything beyond a bit of anxiety-- and aggravation because I just spent money yesterday trying to get that fixed, among other things. Something called a "pass code detector" which sense if the key has been turned was replaced.

This morning--- yep--- it lit shortly after I got rolling and has rarely been off since. I DO have the light go "off" when I turn the key to "run" and hold there before starting, and once started the engine runs like a champ.

1998 Chevy 2500 with the 5.7 engine, but from what I dig up elsewhere I reckon that might not mean much.

Turtle · Aug 19, 2015

This could be any number of issues. If it was Passcode related, the engine probably wouldn't start, since that's what it's designed to do. You might try the Passcode Relearn Procedure and see if that helps, but it probably won't make any difference.

Another thing to try is disconnect the battery (all of them) and ground the positive cable for at least half an hour. That will reset the computer and might clear the light.

Could also be a door striker switch fault. They aren't in the posts, they are built into the latch mechanism in the doors, so it's hard to get to them to check. However, open a window and then lock the system with a key fob, then reach in and unlock the door manually and open it. The horn should go off and lights flash, like you hit the panic button. Repeat for all doors. If one doesn't react, you may have located the problem.

Could be an ignition switch that needs to be replaced or a loose connection around the ignition. If you remove the plastic panels above the ignition, check for good connections, especially the one right on top of the ignition key cylinder. The one on top can become corroded or work lose and can cause security light problems (though, if it's badly corroded or has worked too far loose, the engine won't start, because that carries the key-turn signal to the Passcode Detector).

mjmsprt40 · Aug 19, 2015

OK--- the door switch in the rear door is faulty-- I know this because the interior lights stay on unless you press the bypass switch. Also because I saw a broken piece fall out of that mechanism one day recently. I can forget about key fobs--- this thing is old-fashioned enough that it has hand-crank windows and manual-- not electric-- locks. The ignition switch--- a possibility. A van this old with 578K miles on it likely could have a problem there--- though I would think the mechanics might have checked that the other day, it's possible it got by them.

My main concern is whether this machine is going to give me an unwelcome surprise--- like refusal to start while under load. It hasn't failed to start so far, and once the engine is running the light appears to make no difference.

Turtle · Aug 19, 2015

When the engine starts and the light stays on, it usually means there is a mechanical problem somewhere in the security system. For keys with a fob, the resistor not being read when turning the key is one of those kinds of problems. If you have a totally bare key with no cover on it, then it's probably not a resistor. If yours has a cover that could conceal a chip, try another key to start and drive the van.

Cleaning out the key cylinder with contact cleaner may fix it, as over the years it's amazing how much metal power accumulates in there. There could be enough in there to move the cylinder slightly so that an electrical connection isn't being made.

Turn key to ON position (not running) and sit there for about 10 minutes. After about 10 minutes the light will turn off. Within 5 seconds, turn the key to OFF and back to ON again. DP that process for 3 cycles. After the 3rd time, when you turn it back to ON, the light should be out. That resets the Passcode. Couldn't hurt.

My money is on the ignition cylinder or the switch. When cleaning the key, key cylinder or changing keys does not help, a key cylinder problem is likely. Either the contacts in the cylinder get worn out or the wiring in the column fails.

There are people who drive with that light on for months or even years. Most of those people aren't using their vehicle in expediting, though, so like you I'd want to track down the problem for the very reason of your main concern.

mjmsprt40 · Aug 20, 2015

The cylinder is looking likely, actually.

I note here that if I turn the key to the run position, without starting-- the light goes out after about 3 seconds. Then- I've started the engine. Light stays out for a varying length of time, but yesterday it was never "off" for more than 5 minutes after engine start. I could try a passcode reset (thanks for telling me how) but I have a sneaking suspicion that's not where the trouble really lives. Old wiring-- suspect connections--- key cylinder that's seen its better days-- that's where my suspicion is at this moment now that you've suggested it.

Turtle · Aug 20, 2015

Yeah, like I said, if it's a Passcode problem, the engine won't start. When the engine starts and it drives fine except the security light is on, it's almost always the cylinder and/or the ignition switch. People who have damaged or worn keys will replace the cylinder, then suddenly they have the same exact security light problem. That's a problem with the connection between the cylinder and the switch. But most of the time when you get the light and haven't replaced the cylinder, that's the culprit. Good luck!

Greg · Aug 20, 2015

Turtle said:
Cleaning out the key cylinder with contact cleaner may fix it, as over the years it's amazing how much metal power accumulates in there. There could be enough in there to move the cylinder slightly so that an electrical connection isn't being made.

If you go with cleaning the cylinder, I would be near by a place to get a new one. Some of the powder that accumulates in there, when removed, can make a key not work. If the worn key and worn tumblers in the cylinder are the source of the powder, removing it may remove the key's ability to turn the cylinder.

Also, there have been reports of heavy key chains pulling on the ignition causing premature wear from the excess weight.
Good luck.

mjmsprt40 · Aug 22, 2015

I had a long run (about 1100 miles round trip) since I posted here last. Mostly, the light was on within moments of start-up. However, there was a solid period of 300 miles Thursday night/Friday morning when the light stayed off. It came back on shortly after my last fill-up of that trip and did the usual thing of turning on within moments of start-up.

At this point I'm inclined to think it's a nuisance, but one I will have to keep an eye on.