Hi , I have a 2003 2500HD Silvarado PU. The Battery light keeps coming on
and remains at different levels of intensity [ the brightest when the
vehicle is sitting ] The dealer put a new battery in and the light stayed
off for about a half hour , for the ride home. The Voltmeter stays around
14V , and charging appears normal, the vehicle also starts and runs fine. I
would think if there was a problem in the charging system that the Voltmeter
would read low [ around 9V ] Does anyone know, specifically, what the
battery light indicates ? Could this be an overly sensitive light and just a
false alarm? Anyone have any idea what could be going on? Thanks.....
The battery light is controlled by the pcm in this vehicle.... I seriously
doubt the alt is bad... There is a sense wire coming from the alt going to
the pcm... this is monitored by the pcm to see if there is an issue... I
have had a few with this problem and it can be difficult to correctly
diagnose,although a battery wouldn't have been my first choice... If the pcm
sees a problem, then it tells the cluster via the class2 data line to
illuminate the battery light... I would bring it back to the dealer, but I
wouldn't have a panic attack if they took a while to get it in... as long as
you are seeing good voltage(14v) then you won't be stranded... 1 was a
wiring issue(ran new wire from pcm to alt), and the other one ended up being
an internal problem in the pcm.... ....if you need more specific info, let
me know.... Bobo
As a retired GM service manager it is saddening to see that an owner of a
new truck has to resort to posting here for help with a new vehicle warranty
repair problem. If I were running a service dept. that this issue pointed
to, I would be embarrassed and bend over backwards to resolve the problem.
On this vehicle, the light is turned on or off by the instrument cluster,
based on messages from the powertrain or body control modules that tell it
the charging system voltage is below 11 volts or over 16 volts. It should be
either full on or full off, not varying in brightness. I would put a
voltmeter on the battery and see what it reads with the engine running, the
dash gauge is not that accurate. It should be around 14 volts or so with no
accessories turned on. If the charging system voltage is normal, I would
suspect something screwy with the instrument cluster.
Robert Hancock Saskatoon, SK, Canada
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