Passlock II system (How to disable it)

Ok here's a good one:  This 2001chevy truck was involved in a roll-over, not a great deal, the funny thing is that the truck no longer starts. THERE'S NO SECURITY SYSTEM INSTALLED but the car acts as if the passlock system is damaged somehow since the car starts fine for about 2 seconds and then ir shuts down just like when you cut the yellow wire from the passlock. Anyway I need to know if someone knows the concept beyond passlockII and how to possible disable it so I can get this car running again no matter how.  I checked with the dealer and there's no fuel cut-off switch like the fords where if something like that happens you need to reset the switch. So any good technicians/mechanics/installers/troubleshooters like me who like to play around with wires outhere I really need some help. Could it be a damaged computer?  All of the iginition wires as well as the starter are fine and there are no blown fuses inside or outside. Like I said the car starts fine but after 2 seconds it'll turn off just like when you mess with the passlock. HELP PLEASE!

When the car starts and dies, leave the key on and look at the dash. If Passlock is the problem, the security light will be probably flashing on and off.

To disable it for short term, cut the yellow wire and cap off both ends. Then put the key in the ignition with the door closed and crank it, the truck will die. Then leave the key in the run position for 15-20 minutes. The check engine light may or may not turn off. After the waiting then try to start the truck, this time it should start up unless there are other problems. You can also try this without cutting the yellow wire and this will program a new key.

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Certified Security Specialist
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Program a new Key? Passlock II doesnt use special keys. One time I was working on a blazer and I turned over the PCM to more easily access the tach wire, and before I turned it back over a locked it into place, I tried to start the car and it did the same thing you are talking about so I thought somehow my passlock bypass needed to be programmed again. Then I realized I just needed to turn over the PCM.

So, maybe something got damaged in the PCM, that will need to be replaced. I am just speculating though.

Good luck.

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J Rilla

Owner/Installer

what do you mean you turned it over? you mean you removed the computer from its place and because of that the car wouldn't start? does it have level sensors? I don't know about that but I'll check on those things tomorrow.  The guy who was working on the truck before me did remove the computer and it was hanging when I got there, he was testing with "computersafe test lights" I hope he didn't screwed anything in there. Thanks guys.

It could have something to do with the airbag system... did the airbags deploy when the truck rolled over? If so, the ECM may need to be reset despite the fact that the airbag units themselves were replaced...

No the aribags are intact the only thing it broke was the bed fenders since they're made of fiberglass. So how do I reset the ECM?

Yeah I just unfastened it and turned it upside down since the tach wire was in the most difficult harness to reach. It started right up though after I turned it back right side up.

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J Rilla

Owner/Installer

Tried everything I was told, still the same. The security light stays on all the time I'd like to find a solution to disable Passlock II for ever. if anybody else has something to share please do. Thank you

anybody? come on I'll even pay a service fee whatever it takes (yes that's how desperate I am) I'm sure someone knows the way around it. Send me a message

why did the guy have the puter ou if there was only damage to teh fenders? Or was he trying to correct the same problem you are now working on?

Leaving the key in didn't work huh. Has the battery been disco'd and let it sit there for a 1/2 hour or so. Maybe it's the same thing as mentioned above with tun teh ECM upside down. I think he might be right. The unit might need to be put on Chevy's puter interface and reset. Guess it's a safety feature to stop gas from pumping out when the car is upside down.

auex] wrote:

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To disable it for short term, cut the yellow wire and cap off both ends. Then put the key in the ignition with the door closed and crank it, the truck will die. Then leave the key in the run position for 15-20 minutes. The check engine light may or may not turn off. After the waiting then try to start the truck, this time it should start up unless there are other problems. You can also try this without cutting the yellow wire and this will program a new key.

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Try his method again this time do not "crank" the truck. Just put the key to "IGN" wait 30+ minutes and then try and crank it.

Have you checked to make sure the ECM is rightside up? Pull it out and turn it over as mentioned above. Maybe it's in backwards.

Sorry, 3 in a row.

Goto commandocaralarms.com or DEI (555I or 555L) and look at the instructions on how to bypass the passlock. Find the resistance value and just go to Radio Shack and get a resistor and connect it permently. If it still don't start the you know it's deeper in the computer.