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Old 11-27-2020, 08:09 PM   #1
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2017 Sierra voltage gauge

Hi
Just wondering if anybody can tell me what the little red light at the top of my voltage gauge is for.
Just noticed it the other day.
Voltage is reading 14 volts so that's ok.
I have owned this 2017 GMC Sierra for 3 years and never noticed the light before.
The light is very small but easy to overlook.
Any ideas?
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Old 11-28-2020, 07:24 AM   #2
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Quote:
Originally Posted by Ted Lambert View Post
Hi

Just wondering if anybody can tell me what the little red light at the top of my voltage gauge is for.

Just noticed it the other day.

Voltage is reading 14 volts so that's ok.

I have owned this 2017 GMC Sierra for 3 years and never noticed the light before.

The light is very small but easy to overlook.

Any ideas?
Do you have a picture? If it is a small round light, in my 2013 gmc it was a light that said the security system was on and it would come on at weird times...i think i had an ecm problem, but i sold the truck.
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Old 11-28-2020, 04:41 PM   #3
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Quote:
Originally Posted by Ted Lambert View Post
Hi
Just wondering if anybody can tell me what the little red light at the top of my voltage gauge is for.
Just noticed it the other day.
Voltage is reading 14 volts so that's ok.
I have owned this 2017 GMC Sierra for 3 years and never noticed the light before.
The light is very small but easy to overlook.
Any ideas?
I would suspect it's an alert for high or low voltage. It's hard for even a tech like me to be sure because there are different option levels and instrument clusters out there. For sure this is in your owner's manual, you know, that brick-like 500+ page thing that should be in your glovebox?
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Old 11-28-2020, 05:28 PM   #4
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The manual says the light comes on when its outside its operating range.
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Old 11-29-2020, 11:51 AM   #5
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The manual says the light comes on when its outside its operating range.
I have read the manual from front to back and I don't see this. Could you please give me a page # to reference it?
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Old 11-29-2020, 11:55 AM   #6
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I would suspect it's an alert for high or low voltage. It's hard for even a tech like me to be sure because there are different option levels and instrument clusters out there. For sure this is in your owner's manual, you know, that brick-like 500+ page thing that should be in your glovebox?
I have read the manual and I don't see anything about it.
I have been a tech for 45 years and know how to read shop manuals, can't find anything in the service manual either!
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Old 11-29-2020, 12:01 PM   #7
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Originally Posted by kdauto View Post
I would suspect it's an alert for high or low voltage. It's hard for even a tech like me to be sure because there are different option levels and instrument clusters out there. For sure this is in your owner's manual, you know, that brick-like 500+ page thing that should be in your glovebox?
I have read the manual and I don't see anything about it.
I have been a tech for 45 years and know how to read shop manuals, can't find anything in the service manual either!

My voltage is good at 14 so high or low voltage warning doesn't quite fit unless 14 volts is too high which I doubt.
I only noticed this light after I changed the battery. Just because I was looking at it. The light is so small it would never warn anybody.
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Old 11-29-2020, 12:22 PM   #8
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Originally Posted by Ted Lambert View Post
I have read the manual and I don't see anything about it.
I have been a tech for 45 years and know how to read shop manuals, can't find anything in the service manual either!

My voltage is good at 14 so high or low voltage warning doesn't quite fit unless 14 volts is too high which I doubt.
I only noticed this light after I changed the battery. Just because I was looking at it. The light is so small it would never warn anybody.
Well, you are very unclear on if you need info only or if there is a problem, such as the warning light is now on and was not previously.

There are 4 instrument cluster options on a 2017, and at least 4 engine options. We don't even know if this is a 1500,2500 or 3500.

There are several battery options, and we have no idea how you replaced the battery. There are AGM and non-AGM batteries, and not necessarily interchangeable. Did you use a battery backup when swapping it out? I am not sure on your particular truck (we still have no idea other than GM and 2017) but some vehicles require battery registration these days. GM has several charging modes that are BCM and PCM controlled...it needs to know what type of battery and if it is new. Some deduct this info from data collected, others need a manual nudge or battery life sucks.

Did you scan for codes in all modules? There may be a relearn or reset procedure for the charging system.

"14 or so" volts is not a valid spec. 14.1 steady is probably weak on a GM, 14.9 steady is probably too high. Is the "repair charging system" message indicated too?
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Old 12-02-2020, 03:17 PM   #9
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Well, you are very unclear on if you need info only or if there is a problem, such as the warning light is now on and was not previously.

There are 4 instrument cluster options on a 2017, and at least 4 engine options. We don't even know if this is a 1500,2500 or 3500.

There are several battery options, and we have no idea how you replaced the battery. There are AGM and non-AGM batteries, and not necessarily interchangeable. Did you use a battery backup when swapping it out? I am not sure on your particular truck (we still have no idea other than GM and 2017) but some vehicles require battery registration these days. GM has several charging modes that are BCM and PCM controlled...it needs to know what type of battery and if it is new. Some deduct this info from data collected, others need a manual nudge or battery life sucks.

Did you scan for codes in all modules? There may be a relearn or reset procedure for the charging system.

"14 or so" volts is not a valid spec. 14.1 steady is probably weak on a GM, 14.9 steady is probably too high. Is the "repair charging system" message indicated too?
No problem I just thought you needed an excuse to vent off!
If I had a problem I would have indicated it I just asked what the red light was for?
Even the GM dealer couldn't answer my question.
I could give you in info on the truck up the ying yang and it wouldn't have helped.
My question was about the gauge.
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Old 12-02-2020, 05:10 PM   #10
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I gave you the answer already!

I wasn't venting, but rather, trying to help. Helping someone on these things requires a lot of specific info. Sorry for bothering but I gave you the answer.

If you looked through your owner's manual properly you'd find it. Any GM-trained tech should have the answer as well, but I'm not surprised.
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Old 12-04-2020, 08:53 AM   #11
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I wasn't venting, but rather, trying to help. Helping someone on these things requires a lot of specific info. Sorry for bothering but I gave you the answer.

If you looked through your owner's manual properly you'd find it. Any GM-trained tech should have the answer as well, but I'm not surprised.
Not so! The light you are referring to is a battery warning light that you see when the ignition is in the on position but engine not running.
The same light that warns of a malfunction in the charging system.
If you start the engine the test mode for the charging system is deactivated.
It is not a warning light as you would expect.
It is in the voltage gauge and not really part of the cluster.
When I last had my vehicle serviced and I pointed out the light to the service manager he had everybody in the shop scratching there heads.
I really wish I had not brought it up as you went into a trouble shooting mode because you assumed I had a problem. Which I don't!
I didn't see a need to bore anybody with readings from my Fluke meter.
You read far to much into my question.
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Old 12-04-2020, 10:08 AM   #12
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Nope, that was not what I was speaking of. There are actually at least 3 ways charging system warnings pop up on these modern GMs. I wasn't speaking of the battery symbol lighting up.

At any rate, no use wasting time on a non-issue.
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Old 12-05-2020, 12:18 AM   #13
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Computer controlled voltage systems will drop the voltage rather quickly after startup, as opposed to the constant 14.4 or so that the old systems ran at. Its quite possible for a computer controlled system to drop to the mid 13's as soon as it senses the battery topped off from the last start. This is a fuel saving method the auto makers use, the alternator doesn't work as hard. the light may be telling you the voltage is out of range, too high probably, but you need to look in the OWNERS manual and find the instrument cluster pic that identifies everything and see what it has to say.

Charles
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