Passlock (security)

[GregGP]

Does anyone know what it takes to properly repair the security system when it will not allow me to start the car until I do the whole ten minute thing? It's a 2002 Grand AM 3.4L. I have done the trick of cutting the wire while the car is running and put a switch in it, but now my wife wants me to completely fix it so that the security system works again. Thanks.

[GregGP]

I mean is it usually the BCM, or the ignition switch?

[thephantom1492]

ignition switch

however, if you want to make her beleive that you fixed it, just put a resistor on the yellow to black wire, bcm side. Do a 10 minutes relearn.

The resistor is a 5 cents fix. the ignition is 100-200$, depending on where you get it (and a 450-500$ at the stealer... err I mean dealer)

resistor value: 470 to 10k ohms, 1/4W is fine. The value isn't critical at all, actually, any value in that range work

[GregGP]

Awesome. I'll probably do that Pahntom, Thanks.. How does that work with the security system though? I'm just worried that if I do the resistor trick, that the car will get all jacked up when the factory VATS arms..

[thephantom1492]

The passlock2 system work by having a magnet on top of the pins in the ignition. when the key lift the pin, the magnet get closer to an hall sensor (magnetism sensor). Based on the magnet strength, the sensor have an higher or lower resistance. The BCM learn that resistance, then at every startup it compare the learned one with the one it see. If the value do not match it think someone is playing with the wires and try to jump start it.

The problem is when there is too much wear, the height isn't stable, so is the strength, so the resistance.

If you put a resistance, the BCM will always see the same one all the time, so won't go in theif deterant mode.

[GregGP]

OK, I'll look at it again.. You're sure this procedure works with a 2002 model? There is not a resistor built in to the key on this one.

[thephantom1492]

you have a passlock 2 system, which use hall sensors, which based on the height of each teeth on the key produce a different resistance.

And I've done the mod on a 2002 se, work flawlesly since then.

[GregGP]

Well, it's a 2002 SE that I'm working on, so sounds like it should be good. Thanks.

[GregGP]

OK, well, I cut the black wire and put a resestor between the black wire and the yellow wire. The car still starts, and the security light still stays on the whole time. Should I have done something different?

[thephantom1492]

you put the resistor on the wires going to the bcm right? or the one that go to the ignition key?

[GregGP]

Yes, I put the resistor in the BCM side of the cut wires. Actually, I put two 1/8W 1K Ohm resistors in parallel in between the black and yellow wires. I didn't unhook the battery or anything though.

[GregGP]

Was I supposed to bring it out of the 'fail enable' mode first or anything?

[thephantom1492]

The weird thing is: the car shouln't have started. However, since the passlock was faulty maybe that's why... Try a 10 minutes relearn maybe. As in: put key to run (but not start), wait 10 minutes or so (or more).... then off 5 seconds, then start the car...

if it still stay on, turn to "run" and mesure the voltage across the resistor. If you get 0V then there is a problem with the wiring...

btw, a single 1/8W 1k would also have worked. but 2 in parallel is still fine... I would personally have threw only one (at 1k there is 0.025W, or 1/40W maximum, it's actually even less)..

... I wonder if 500ohms would be too low... shouln't be, they say 470 to 10k... so... it's in the (low end of the) range

[GregGP]

We'll, here's the curent situation: I re-connected everything back to the way it was from the factory, and the car started and ran fine (no security light). Then I disconnected the yellow wire and the car wouldn't start (as expected). Then I unhooked the black wire and put a single 1/8 W 1K Ohm resistor between the black and yellow wires (BCM side) and the car started fine again with no security light. Does this mean that the BCM is probably going bad? And if so, do you think this resistor will keep it 'happy' for a while?

[GregGP]

I think I'm going to let it ride the way it is for now. I would like to unhook the battery to do a real test of the worst case scenario, but I don't have the code for the stereo on hand, so maybe I'll do that later. Thanks for your help though Phantom!