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GM Bob
GM Bob, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1061
Experience:  30 plus years. experience as GM technician, ASE Master Technician and GM Certified.
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Service theft deterrent light is on, i have scan tool but

Customer Question

service theft deterrent light is on
JA: Do you have the trouble code? Do you have a code reader or scan tool?
Customer: i have scan tool but there is no code
JA: I'll pass this info along to the Chevy Mechanic so that he can get you a quick fix. What is the model/year of your Chevy?
Customer: 2008 silverado 2500
JA: Are you fixing your Silverado yourself? What have you tried so far?
Customer: yes, The key cylinder was replaced with new key and theft deterrent module. I have tried the relearn procedure many times with no luck.
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 3 months ago.
Category: Chevy
Expert:  Chris (aka-Moose) replied 3 months ago.

Welcome, I'm Chris (aka Moose), my normal schedule online is around lunch and after dinner till early morning.

Are you trying to reprogram with or without a scan tool?

Will the module communicate with the scan tool?

Customer: replied 3 months ago.
My scan tool in using is efi live so I'm not too sure of it's capabilities. I've taken the ignition switch out that the key cylinder rotates and put everything back together with the original key back in the ignition and rotate the wheel on the ignition switch to start the truck and the light is off that says service theft deterrent system. Then I put the new key in and it starts and works fine but the light comes back on. I'm wondering if there isn't a problem with the key itself but I'm not sure why the key will start the truck if there was a problem with the key. I have put everything back together and it works fine but the light is annoying. I took it to the dealership for them to look at it but they said the theft deterrent module was bad so I put the original one back on and verified it works with the original key.
Expert:  Chris (aka-Moose) replied 3 months ago.

So if I understand the truck starts with the new key and theft module, and it starts with the old key and old theft module?

Customer: replied 3 months ago.
it will start with both keys and module but the old key isn't the right one for the new key cylinder so it won't turn the ignition switch so I have to take it apart to start it with the key just sitting in the cylinder. The new theft module I guess was no good because that is what the dealership said and the light stays on regardless of which key I use.
Customer: replied 3 months ago.
I had to replace the cylinder the key goes in because the old one was locked up. The new one I ordered came with a new theft module and key.
Expert:  Chris (aka-Moose) replied 3 months ago.

That is what I am leaning to as well. The new theft module is faulty and causing the issue with the light staying on with the vehicle running.

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Thanks for using Just Answer, Chris

Customer: replied 3 months ago.
I kind of knew the new one was no good so I put the old one on and the light goes away but I have to use the new key because the old key won't work in the new cylinder. I programed the new key and it starts but the light won't go away.
Expert:  Chris (aka-Moose) replied 3 months ago.

So now with the old module, new key, the light stays on. So with both modules the light is staying on now?

Customer: replied 3 months ago.
with the new key the light stays on regardless of which module I use.
Expert:  Chris (aka-Moose) replied 3 months ago.

That makes no sense, it should not even start with that scenario. I would try new keys programmed to the vehicle.

Customer: replied 3 months ago.
That's what I think is that it has to be the key that's the problem, I just don't understand how everything works with the key besides the light being on. I guess I will try a new key and let you know.
Expert:  Chris (aka-Moose) replied 3 months ago.


Expert:  Chris (aka-Moose) replied 3 months ago.

Hello again Chris here,

  1. I have to assume you were not pleased with my help, because you have not replied or rated the post.
  2. What would you like to do regarding your question now?
  3. Do you still need help? Please reply I want you to get equal to or more than what you paid for.
  4. This post is coming up on the 7 day mark where it times out. That can prevent me from being able to post answers to your replies.

Thanks Chris

Customer: replied 3 months ago.
The new key didn't fix it.
Expert:  Chris (aka-Moose) replied 3 months ago.

I am out of ideas, I will opt out and let another try.

Expert:  GM Bob replied 3 months ago.

Hello my name is ***** ***** I can help.

When you replaced the new module did you have it programmed? This is not the key leaning procedure.

Can you post your VIN number.

Thank you

Expert:  GM Bob replied 3 months ago.

Did you still need help?