Theft mode

[mattillac]

The status of the security light is probably important.

Not sure this if official, but I do believe this is what you'd be looking for.

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• If the PASSLOCK(TM) sensor was replaced the SECURITY indicator will flash for the 10 minutes duration.
• If the EVO/PASSLOCK(TM) module was replaced, the SECURITY indicator will flash for a few seconds and then remain ON for the remainder of the 10 minutes duration.
• If the VCM/PCM was replaced with a new programmed VCM/PCM and connected to the vehicle for the first time, the vehicle will start and this procedure may not be necessary.
• If the replacement VCM/PCM was connected to any vehicle at any other time, even momentarily, the SECURITY indicator will flash for a few seconds and then remain ON for the 10 minutes duration.

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Thought that I read somewhere that all the modules are refurbished now, like no new ones are available, meaning that they would have been connected to another vehicle previously (flash for a few seconds and then remain ON for the 10 minutes duration).

Have to wonder if the OP did the full "30 minute" relearn procedure for the replacement passlock module.

FWIW, if the light never flashes and stays on constantly (it ain't learning nothing).

As others have said, probably best to "tune" those problems all away.

But the parts are available and there are well written procedures for testing the components, if someone is dead set on fixing it.

I believe everything you need to know (diagrams/troubleshooting procedures etc) is in this here manual, just save and load the PDF then search for the word "passlock", it is referenced 376 times there, or go straight to section 9D.

1998_GMT-98_CK-1_SERVICE_MANUAL-VOLUME_1_of_4

MediaFire is a simple to use free service that lets you put all your photos, documents, music, and video in a single place so you can access them anywhere and share them everywhere.

www.mediafire.com

The full list of manuals can be found here.

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

Thanks to GMT400.

Best of luck.

 

[618 Syndicate]

I think I found some answers on the net-as I understand the symptom of passlock's fault is "crank no start". I had it once-and I had no idea the truck was equiped with some anti theft device. I guess when I'm done with covid I have to check if my truck has it.

Your truck 100% had it from the factory.
The "crank no start" is actually crank, start, immediately die, and it isn't a fault in the passlock, that's what it's supposed to do. It's an anti-theft device.

 

[HotWheelsBurban]

Your truck 100% had it from the factory.
The "crank no start" is actually crank, start, immediately die, and it isn't a fault in the passlock, that's what it's supposed to do. It's an anti-theft device.

Yes it will crank and fire, but it dies in a couple of seconds. This is because the passlock module and the PCM ( powertrain control module) have decided the truck is being stolen, and shuts the power off to the fuel pump relay.

 

[SUBURBAN5]

Do you think 99 Tahie would have it? What are the symptoms of this thing failing? And forgive my ignorance but what's the DRL diode? Or some more details on the location of this thing please?

If a united states model then yes. If European idk lol. It's a silver looking metal thing that has finn's like the ecm under the hood. This drl module is located pretty much in the center of the dash right next to the defrost vent. Left side of radio. Very hard to fish out or un bolt lol

 

[someotherguy]

For some clarification, the DRL diode is GM part # 15043231 and if you do an image search on that # you'll see a whole whack of excellent pictures to help you identify it.

For an example of the TDM, you can image search part # 19352768 - just be aware there are many varying part #'s for the TDM depending on application; don't be tempted to just buy one and try it. And don't fall for any of the "bypass" modules. Trust me.. just have a tuner remove the security from your PCM.

Richard

 

[Dariusz Salomon]

If a united states model then yes. If European idk lol. It's a silver looking metal thing that has finn's like the ecm under the hood. This drl module is located pretty much in the center of the dash right next to the defrost vent. Left side of radio. Very hard to fish out or un bolt lol

Thank you-and btw there was never european Tahoe,Silverado or Suburban.

 

[Dariusz Salomon]

Your truck 100% had it from the factory.
The "crank no start" is actually crank, start, immediately die, and it isn't a fault in the passlock, that's what it's supposed to do. It's an anti-theft device.

Of course I understand,that it's what it's suppose to do however if you using the key that is a correct key and it doesn't kick in then it's a fault. Thanks for explaining the symptoms to me. It opens my eyes to a potential solution if it happens. Which leads me to another question-once the truck starts as normal can the lose in communication between the passlock and the key result in the engine to cut out?

 

[Dariusz Salomon]

For some clarification, the DRL diode is GM part # 15043231 and if you do an image search on that # you'll see a whole whack of excellent pictures to help you identify it.

For an example of the TDM, you can image search part # 19352768 - just be aware there are many varying part #'s for the TDM depending on application; don't be tempted to just buy one and try it. And don't fall for any of the "bypass" modules. Trust me.. just have a tuner remove the security from your PCM.

Richard

Thanks for the parts numbers and advice-it's important.

 

[SUBURBAN5]

Thank you-and btw there was never european Tahoe,Silverado or Suburban.

I'm referring to holden/brazil/mexico

 

[618 Syndicate]

Thank you-and btw there was never european Tahoe,Silverado or Suburban.

There were RHD Holden versions though, any of those around over there?

Of course I understand,that it's what it's suppose to do however if you using the key that is a correct key and it doesn't kick in then it's a fault. Thanks for explaining the symptoms to me. It opens my eyes to a potential solution if it happens. Which leads me to another question-once the truck starts as normal can the lose in communication between the passlock and the key result in the engine to cut out?

The way you worded it made me question if you knew that. Wasn't trying to be a knob.

I suppose it could potentially, but I've never heard of it happening like that, I don't think it is a constant communication between the two. It sees what it needs to see and allows the truck to start. It would be more likely to just refuse to restart the next time it was switched off.