Anti-theft activated

2011 GMC YUKON
200,000 MILES • 5.3L • 5 CYL • 4WD
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CMCNABB77
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Truck is in anti-theft lock. I tried to rest doing the three on and off for 30 minutes methods. My problem is the light never went out to do step two over. Does this mean the anti-theft module is bad?
May 21, 2021 at 11:37 AM
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KASEKENNY
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This could be a umber of things so we need to start with checking for codes.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If there are no codes, then we are going to have to run through the testing below for this issue. It could be an issue with the BCM or even the IPC so we just need to see what turns up with this and we can go from there.

Let us know if you have questions. Thanks
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May 22, 2021 at 5:30 PM
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CMCNABB77
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I did the test you sent with no luck. I order the scanner you mentioned and it reads no codes or failures. The security light does not blink when trying to start. It remains on. I tried everything I can think to try. Could it just be the chip in my key is bad? My fob will unlock and lock. Also set the alarm. Seem like it's the key maybe? Thank you for the help i'm lost here!!
May 25, 2021 at 7:48 PM
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KASEKENNY
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Okay. It could be a key issue but let's take a step back. The process that you laid out I think is for the wrong system. You have a Passkey III system so I attached the info below on this process.

Let's try this and and go from there.
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May 26, 2021 at 6:00 PM