2002 Tahoe passlock security issue, draining battery?

lostinnd said:

So I have a dreaded passlock bug in my Tahoe now. Earlier this summer I had to replace the ignition switch wiring (turns out that wasn't the issue anyway) and ever since then the security light is on constantly and the battery dies after a day or so. It has a brand new battery and alternator, no lights or anything else stay on. It starts fine once I charge the battery so the passlock isnt interfering with it that way.

Would changing the ignition switch wiring cause the security light? YES I am assuming the passlock problem is killing the batteryNO. Is there a bypass for the passlock?YES I found some info online about putting a resistor in the wires that go to the BCM but wanted to make sure.

Any advice would be appreciated, the tahoe is kinda worthless now as I don't have time to jump it everyday and I really want to get it on the road again!

Thanks for the help!

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Ponchonutty said:

I've done extensive work on the Passlock systems in these GM vehicles. Google my screen name and PASSLOCK and you will have hours of reading. I would bet you have something else going on with the battery draw. I know many of these trucks have issues with battery cables rotting on the inside out. My '01 Silverado went through 3 GM batteries until the dealer replaced the battery cables at my request. Never changed a battery until 10 years later.

You could also have a bad ignition switch. Just because it is new doesn't mean it's any good. You can try to do the testlight method between the battery and cable to see what fuse you have to pull until the light goes out. If you can not find anything, you will need to meter it to see if the system is properly being charged. Now, you could get lucky and go to Autozone or other parts place that has one of those high tech battery tester/scanner to see if it can pick up the problem????

Lastly the passlock system.... If that light is on solid as you drive then you have a failure. Surprised that it starts at all when you have to jump the truck to start.

To permanently bypass the system you will need a resistor (usually between 500-1700ohms works best) to be installed on the cut end of the YELLOW wire that goes AWAY from the ignition switch with the battery disconnected. The other end goes to the black or orange/black wire. I also like to run another wire from that black or orange/black wire to chassis ground. Once you have that, connect the battery and try to start. Hopefully it won't and the security light flashes. If so, leave ignition on for 10 minutes or until the light is either solid or off. Turn ignition off, count to 3 then crank it again. It should start. If not, repeat the above until it fires.

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