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Security light on why?

Tiny
PETERT1943
  • MEMBER
  • 2 POSTS
I followed your instructions but I still have the same problem.
The security lights stays on all the time and the headlights will not work. Dome light and cab light will not work. If I disconnect the battery for a time and when it is reconnect the the light work until the security light comes back on.
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
You will need to scan it for codes, must be a stored code for the security system. Other thing you might check is all fuses and connectors. Associated with ignition and security.

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

https://youtu.be/YV3TRZwer8k
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
ISSAC ANDERSON
  • MEMBER
  • 1 POST
  • 2000 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 320,000 MILES
Trucks been running good. Battery is less than a year old and alternator is little over a year. Shut the truck off and we started it back up the battery light was on, the security light was on, gauges quit working. Alternator is charging at 14.4v. Truck cranks and runs good even with these issues.
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
This sounds like the cluster is the issue. However, we should start with checking for codes.

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

Once we know if there are codes or not we can jump into the cluster issue.

Basically the way this works is these systems all run through or are displayed through the cluster. The fact that the security light is on but the vehicle still starts, or the battery light is on and the alternator appears to be working shows that the actual systems are not the issue. It is most likely the cluster itself.

Let us know and we can go from there. Thanks
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
ERICVS
  • MEMBER
  • 1 POST
  • 1999 CHEVROLET SILVERADO
  • 6.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 230,000 MILES
Did an engine swap from the 4.8 to a LS1 350 out of a C5. After putting the motor in went to turn it over the security came on. Did the relearn didn’t work. Changed out the ignition switch and cylinder. Did the relearn still the same thing motor will turn over but not getting spark. Where do I got from here?
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
So if you changed the engine you would have changed the ECM over from the other engine as well, correct? If you did this then the keys that you are using is still for the other engine control module.

I suspect the only way we are going to fix this is getting generic PCM with the theft system deleted off of it so that when it gets the ignition switch feed that it is not looking for a specific signal and it just starts the engine.

This is pretty common when we do an engine swap and these services are pretty common. In fact, I suspect you can find one where you just send you PCM off and they will remove the theft system and send it back.

If you take a look at the information below you will see how the system works.

Let us know if you have questions. Thanks
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
JOSHUA WAYNE
  • MEMBER
  • 3 POSTS
  • 1998 CHEVROLET SILVERADO
  • 4.8L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
So recently I unplugged the computer in the truck listed above k1500 and left it unplugged for a few days. When plugging it back in the security became engaged and the security light is steady on not flashing. Unable to fix that I wanted to check the obd codes. The tool says no communication with vehicle. Have done some research and discovered the check engine light does not come on at all. The check gauges light comes on for a few seconds but not he check engine light. Where should I start with figuring out why the check engine light isn't functioning and does this immediately mean the PCM is bad? The truck has been running or weeks and haven't ever noticed the check engine light coming on.
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

Did you have the battery disconnected when you unplugged the PCM? Also, if you leave the key in the on position for approximately 10 minutes, does the security light turn off?

Check pin 16 in the DLC to see if there is power present. See the attached pics.

Let me know what you find.

Joe
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
JOSHUA WAYNE
  • MEMBER
  • 3 POSTS
Okay, will do. First thing in the morning. Honestly can't remember if the battery was unhooked or not. Have tried several relearn procedures with the key. Light does not go off. Doesn't even blink.
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
JOSHUA WAYNE
  • MEMBER
  • 3 POSTS
The obd tool isn't self powered however and does power on so I assumed there wasn't a problem at the obd plugging for power.
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

I should have asked this earlier, but can you confirm the engine size? The 4.8L doesn't exist on this vehicle. If you look at the attached picture, it shows what I am seeing. I need to confirm the correct engine to really dig into the wiring schematics. Pin 16 is a standard power supply. That's why I was able to get this far.

Also, if you disconnected the PCM without having the battery disconnected (disconnected or reconnected), it could have caused damage to the PCM.

Let me know.

Joe
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Wednesday, May 5th, 2021 AT 9:41 AM (Merged)

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