2002 Suburban- battery light blinking in message center with no symptoms

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This truck only gets driven a few times a month on random short trips. Yesterday, when I pulled in the driveway, the battery light started flashing. It stays illuminated for about 4 secs at the time.
I hooked up my bluetooth OBDII scanner and I am getting over 13 volts with the truck running. I unhooked the battery with the truck running and I am still getting approx 13V. With the truck turned off, I am getting 12V from the battery. The battery is a Walmart cheapo I bought in November 2019. The truck starts rapidly and I have no symptoms at all.
 
That particular alternator is controlled directly from the PCM. Assuming the engine is a 5.3, the gray wire going into the regulator plug is the wire the processor uses to control the field duty cycle, and the brown wire is what the regulator uses to tell the processor to turn the battery light on. Basically a module, telling a module, to tell a 3rd module to turn on a light. Best way to really diagnose it is with a full function scan tool, as you'd be able to see what the processor is commanding the alternator to do, as well as whether the battery light is being commanded on or not, as well as the voltages at both the processor and instrument cluster. That being said, long story short the problem is likely in the alternator. We've seen a bunch of aftermarket rebuilds for those that will charge just fine but the battery light will always be on, switched to a different brand and everything works fine.
 
Originally Posted by junk1020
That being said, long story short the problem is likely in the alternator. We've seen a bunch of aftermarket rebuilds for those that will charge just fine but the battery light will always be on, switched to a different brand and everything works fine.


Thanks for the tips. This particular alternator is a reman. thats about 8 yrs old. Ill prob just run it until an actual symptom pops up.
 
First of all, never disconnect the battery on a modern computer controlled vehicle.

Second, your alternator is probably bad. Have it tested at a parts store. Takes 2 minutes. Pay attention to the ripple measurement!
 
I had this in my old 2002 2500HD.

There is actually a second circuit for the light as described earlier. My original alternator charged just fine, but the light was doing that.
The problem like said earlier is in the alternator. I replaced mine because, one it drove me crazy and two I towed a lot with it and didn't
want any lights on, on the dash.

You can swap it or run it until it no longer charges.
 
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