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Bad battery, alternator, other? Help!

ADG

By ADG
in Ask A GM Technician

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ADG Enthusiast

ADG

Posted
Posted

So a couple months ago my dash on my 2011 Silverado lit up and then went dead so I figured it was my alternator and bought a new one.   Fast forward to now and it did it again the other day so I warrantied the alternator and still no fix.  When the issue is in its milder form the service traction message shows up.  I noticed that the voltage runs over 15 on startup and when it gets bad I noticed it kept climbing and the I'm guessing ECU protection kicks in and the truck shuts off if in park.  I had my live data scan on ECU voltage but missed how high it got before shutting down.

 

Bad battery?  I still need to do. Battery load test.

 

I'm pretty good at figuring out and doing all my own stuff but this one has me stumped since I think the alternator regulator is ECU controlled.

 

Thanks in advance for any help.  (This is my first post)

 

Andrew

davester Senior Enthusiast

davester

Posted
Posted

could be a bad connection between the alternator/battery/truck (either power or ground), or battery or ecu or possibly other things.  You need to diagnose where the problem is.  I don't know what the diagnostic procedure for it would be for your truck.

 

You might consider getting a subscription to the full-service manual at a site like alldatadiy.com

ADG Enthusiast

ADG

Posted
  • Author
Posted

Thanks, I'll have to check that out.  I did throw a battery in it this afternoon at work because I did a load test and the one in it was questionable.  It never had any problems starting though.

 

After the new battery it did climb up a little high right around 15 volts but then went back down sooner than before.  I'll monitor it on my ride home and go from there.  Fingers crossed although I have my doubts.

 

I'll keep my findings posted as I find out.

 

Thanks,

Andrew

IMG_20200720_084033876.jpg

ADG Enthusiast

ADG

Posted
  • Author
Posted

Ok so update: I did find that when I connect my scanner to check nthe ECM voltage, as soon as it makes the connection shortly after plugged in to the OBD port that is when all the lights/messages pop up on the dash and all the guages shut off.  Also, AC, radio, signals etc also lose power.  It does retain power to the windows and headlights.  Once I unplug my scanner, everything on the dash goes back to normal.

 

Anyone ever experienced this? (Or find a fix)?  I need to check more grounds and fuses, but hopefully it's not a bad ECM...

I hate electrical gremlins...

Andrew

diyer2 Senior Enthusiast

diyer2

Posted
Posted

Electrical problems are a nightmare.

Keep updating please.

:) 

ADG Enthusiast

ADG

Posted
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Posted
7 minutes ago, diyer2 said:

Electrical problems are a nightmare.

Keep updating please.

:) 

Will do.

 

Also, I forgot to mention, even though the dash and other things get shut off, I am still able to access and scan codes/live data.   Until it decides to shut down the entire system.  Then I need to unplug the scanner to restart.

 

Thanks for any help/input,

Andrew

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