Weird security system issue

Tiny
COOLCELL
  • MEMBER
  • 2005 CHEVROLET TRAILBLAZER
  • 297,000 MILES
Okay, This is a weird one! Brace your self!

My vehicle listed above ext sl.
To started the vehicle I have to click the drivers door unlock button or the key fob unlock button then turn the key or nothing happens?

Sometimes if the key is in acc. Click the driver unlock button the starter will try to turn the engine.

I have access to a friends Tech2 and Launch x431 mini pro.

This issue has been going on for a year since I purchased the vehicle just found out it's not normal to starting a vehicle.

I rebuilt the engine 300 miles ago. And also after starting all dash lights go off and no security warnings.

Turn the engine off and restart a minute later nothing happens dash lights go black unless you click key fob unlock or the drivers door unlock then the vehicle will start unless you wait to long.

Been told bad ECM, Bad BCM, wiring issue, caused by the last owner when they installed the after market pioneer radio, bad drivers door switch or control module.

Everything in the cab works fine just this weird start the engine procedure.

Turn key to acc. Click key fob unlock or drivers door unlock button then turn key start engine.

FYI if its the first start of the day and have the key in acc. Click the drivers door unlock the engine starter will turn the engine.

Asking second opinion. Chevrolet dealer said for $400.00 to $550.00 they will let me know the cause not fix it. Cannot afford that! :(

Also check the battery grounds and connections all good.
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Tuesday, November 12th, 2019 AT 9:51 AM

10 Replies

Tiny
KEN
  • ADMIN
Hello,

It does sounds like the BCM is out but to be sure lets do a CAN scan which you can get a scanner from Amazon for about $50.00. here is a video of the job being done:

https://youtu.be/InIlnsjOVFA

Here is how you change the BCM out. Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

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Wednesday, November 13th, 2019 AT 10:02 AM
Tiny
COOLCELL
  • MEMBER
The change out images work great thank you

If I go get my friends Tech2 or his Launch x431 mini pro can that do the CAN scan and reprogram the new BCM? I ask because his house is an hour away. :)
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Wednesday, November 13th, 2019 AT 10:38 AM
Tiny
KEN
  • ADMIN
It should be able to do both with that scanner tech2. Can you please shoot a quick video with your phone so we can see what's going on, that would be great. You can upload it here with your response. Let me know how it goes.
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Thursday, November 14th, 2019 AT 9:55 AM
Tiny
COOLCELL
  • MEMBER
My friend is going to let me keep his tech2 and launch x432 mini pro this weekend until I figure this out this issue or he need them again. Sure he can not help much has to fly back to work in Alaska Sunday and needs to spend some time with his family.
Praying for that simple fix :)
Maybe having map sensor, vacuum, wiring issue, bad ECM or bad BCM, all of above or just a possessed vehicle?
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Thursday, November 14th, 2019 AT 1:17 PM
Tiny
COOLCELL
  • MEMBER
Second video on security system and issues.

Do you think the repair manual help for me out tracking down the issues?
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Thursday, November 14th, 2019 AT 3:04 PM
Tiny
KEN
  • ADMIN
Hello,

Thanks for the video they help a lot. The fact that you need to reset the computer is telling us PCM/BCM what you need to tell for sure is a CAN scan which is the future of car repair you can get one for about $50.00 on Amazon. here is video of the job being done:

https://youtu.be/InIlnsjOVFA

I am leaning toward the BCM here are the instructions on how to replace the BCM. Check out the diagrams (below). Please let us know what happens.
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Friday, November 15th, 2019 AT 5:06 PM
Tiny
COOLCELL
  • MEMBER
Thank you Len. I I just ordered a BCM and have access to a tech2 and luanch x431 mini pro.
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Friday, November 15th, 2019 AT 5:14 PM
Tiny
KEN
  • ADMIN
The CAN scanner would tell us more, lets hope for the best. Please let me know. Also how much was the BCM?
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Saturday, November 16th, 2019 AT 11:04 AM
Tiny
COOLCELL
  • MEMBER
I was free my uncle has a wrecker service it's off a 2005 trailblazer ext sl it was a roll over wrecked vehicle it may be Monday or Tuesday before I work on it. Cancer treatment has me sick
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Saturday, November 16th, 2019 AT 2:35 PM
Tiny
KEN
  • ADMIN
Sorry to hear about the cancer seems like everyone takes a turn in that chair. Let me know how things go with the BCM.
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Sunday, November 17th, 2019 AT 10:45 AM

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