it's just a resistor in the key.has to match the right ohms.think they only did like 7 different ohm resistors.I'm on the east coast by port canaveral/cocoa beach.watched the shuttle go up last night(4:14 am this morning).Craby is right again.if security light comes on when car is already running could be multiple problems.dont know if you saw any of my other posts before/after i changed my opti but that was another thing that would happen.driving along and security light would come on.but would still start if i shut it down and re-tried.if your ses light is coming on randomly you need to get codes read.

 

if u have a body control modual on your yr i think it could be that. it sure sounds like something in the vats or the ignition switch. have it scanned for trouble codes. do some research on the body control modual.

 

gotya so you shouldn't have a factory security system it sounds like a vats issue.

 

also if you have a digital multi meter i would recommend testing your ign wires. should have multiple reds all are constant 12v,Pink is 12v ign(second click),Orange and Brown are 12v ACC, and Yellow is the 12v Starter wire it should only read 12v when cranking the car. if you car doesn't have power at the ign setting on the pink wire then it won't apply power to your starter and i would assume your orange and brown are fine as you said your radio comes on(brown) and orange is for heat/air. also there should be two white wires wrapped in an orange shrink tube those are for your vats wires. if you use the meter to test both sides of your key and then put your key into the ign and test those vats wires and see if you dont get the same reading then your vats system is prob bad.

 

It sounds like you tried to bypass the key's resistor already, right? I'd get back into the steering column and test the resistance on your bypass, as well as making sure those wires are all in good shape. It sounds like you've got a wire in there that may be loose, so sometimes the connection doesn't go through. Make sure the resistance in that bypass matches the resistance of your key pellet.

If all of that is in good working order, it very possibly could be the BCM. I recently replaced my BCM for similar reasons (but not quite the same). Are you having any other BCM-related problems? Do your interior lights ever flash on/off when you've got the door open? Do you ever hear a clicking noise under the passenger side dashboard?

Is the security light on steady, or does it flash at a regular pace, or does it flash like a maniac? If it's going really crazy, it's probably the BCM. Otherwise, it's probably those wires. The BCM isn't getting the right resistance, or isn't getting a constant resistance.

Check those wires before anything else, even if you think they're all good, because that's the cheapest and most likely scenario. Let us know what works.