Weird voltage fluctuations

Mike534x

Well-Known Member
#1
Hi all!

I'm trying to track down a gremlin in the Envoy. Past few months since summer decided to show itself I've been experiencing intermittent voltage drops, usually drops to the 11.5-12 range give or take. Usually only happens for a second or too regardless if I'm at idle or driving. This only happens when I'm running the A/C, and when the voltage does drop the air seems to slow down from the vents and then picks back up again once the voltage hits the 13.5-14 range. I checked the connections running to the battery and back of the alternator but couldn't find anything. I don't recall having this issue last summer or with my previous TB. Is this usually a sign it may be the alternator? or something else entirely? Was also wondering if it may effect the A/C performance, it blows cool but not cold enough to my liking which I assume is an entirely different issue.

Only work I've done so far was replace the blower module, since I lost all fan speeds in June and the module decided to melt itself to the wiring harness. The voltage issue I'm experiencing has been ongoing since about May.
 

MRRSM

Lifetime VIP Supporter
#2
Good Morning Mike...

At first blush.... I'm thinking... BAD GROUNDS

(1) Start by Getting the OEM DIGITAL SERVICE MANUAL for your vehicle (courtesy @Mooseman) from this Link:

https://gmtnation.com/forums/threads/need-service-manuals-get-them-here.361/

(2) Search out the Wiring Diagrams for your GROUND-BONDING STRAP LOCATIONS.
(3) Start with examining and checking for Circuit Continuity on the Battery and Engine Grounds.
(4) Check your Battery Terminals and Connector Wires for ANY signs of Corrosion.
(5) Have Autozone STRESS TEST YOUR BATTERY UNDER LOAD for any Dead Cells.
(6) Have Autozone Check your Alternator Rectifiers and Voltage Output.
(7) Check with NAPA for some HEAVY-DUTY AWG COPPER GROUND WIRES-CONNECTORS.
(8) Locate, Remove the Ground Connectors, Clean Off ALL Rust and Corrosion.
(9) Spray down Bare Clean Metal with Zinc Chromate and Re-Attach the Grounds-Bonding Wires.
(10) Start the Vehicle and measure the performance of the RUNNING Voltage Charging Levels.
 
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Mike534x

Mike534x

Well-Known Member
#3
@MRRSM Would bad grounds really be the culprit? The only time the voltage fluctuates is when the A/C is running. When its off it stays pretty snug at the 13.5-14 range. Though that is a possibility given its age. Are bad grounds usually something that plagues this platform by chance?

I'll have to stop by Autozone and have them do a test on the alternator, I installed a brand new interstate battery about 7ish months ago give or take. Though I botched the job up by connecting the memory retainer to the wrong outlet and blew the megafuse. :duh:
 

MRRSM

Lifetime VIP Supporter
#4
Think about it for a minute... In order to have a COMPLETE ELECTRICAL CIRCUIT... Good Grounds are absolutely indispensable and essential to the Flow of Electrons. Also... If the vehicle shudders and vibrates under the stress and load on the Compressor upon the Serpentine Belt (and possibly place a Drag on the Alternator that will reveal its Weaknesses) whenever the A/C is invoked... a Loose Ground would also be more likely to vibrate...break contact(s)...and re-connect over and over again as well. You might also consider replacing the Serpentine Belt Tensioner as well... since a Worn One will not reflexively absorb the On/Off surging actions of the Compressor Load upon the Belt properly either.

The orders of what is on that List can be changed of course... you could start with a trip to Autozone to investigate #s (5) and (6) if you like... and at least eliminate the possibilities of either a Bad Cell in the Battery... or even a Bad Rectifier in the Alternator...and go from there. If you live anywhere that Bags of Road Salt are dumped on the highways and streets during each Snow and Ice Cold spells.... the integrity of the Grounds needs to be considered for that reason, too.

By the Way...

When you accidentally "Blew That Mega-Fuse"... Don't you think it is possible that the Sudden Short may have either weakened or done something Bad to the internals of the New Battery during that unfortunate episode?
 
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budwich

Well-Known Member
#5
my guess would be a load issue. Since it appears to only happen with AC, my guess would be the clutch is possibly weakening (actually shorts in the winding) causing momentary load spikes, dropping the voltage. Having said that, how are you monitoring your voltage, dash gauge? not very reliable which means it could be hiding other problems related to the overall charge system which only shows up for an "obvious moment" when you have the ac on.
 
#6
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Mike534x

Mike534x

Well-Known Member
#7
Think about it for a minute... In order to have a COMPLETE ELECTRICAL CIRCUIT... Good Grounds are absolutely indispensable and essential to the Flow of Electrons. Also... If the vehicle shudders and vibrates under the stress and load on the Compressor upon the Serpentine Belt (and possibly place a Drag on the Alternator that will reveal its Weaknesses) whenever the A/C is invoked... a Loose Ground would also be more likely to vibrate...break contact(s)...and re-connect over and over again as well. You might also consider replacing the Serpentine Belt Tensioner as well... since a Worn One will not reflexively absorb the On/Off surging actions of the Compressor Load upon the Belt properly either.

The orders of what is on that List can be changed of course... you could start with a trip to Autozone to investigate #s (5) and (6) if you like... and at least eliminate the possibilities of either a Bad Cell in the Battery... or even a Bad Rectifier in the Alternator...and go from there. If you live anywhere that Bags of Road Salt are dumped on the highways and streets during each Snow and Ice Cold spells.... the integrity of the Grounds needs to be considered for that reason, too.

By the Way...

When you accidentally "Blew That Mega-Fuse"... Don't you think it is possible that the Sudden Short may have either weakened or done something Bad to the internals of the New Battery during that unfortunate episode?
@MRRSM I'll stop by Autozone after work and have them do a test on both the battery and alternator! Actually the problems started appearing after the battery swap. When the issue does appear there is no shudder or anything, its as smooth as can be. Only thing that seems to be affected is the A/C and the rate it blows from the vents, when it clears up the air is back to blowing at whatever speed i had it on. Radio, headlights all remain unaffected by this voltage change.


@budwich I have had torque open and an external scan tool connected and have seen the voltage drop seen on the dash show up on the read on the tools.

@Mooseman Was the SARVC available on the 05 model years? I checked my positive and negative cables but don't see anything to what would resemble that module. There is one that is mounted above the fender next to the fuse box that has a cable leading from the wiring that meets at the fuse box and battery cables and snakes its way under the battery itself to the front somewhere. I can post a picture of my battery cables and this box?
 

budwich

Well-Known Member
#8
thanks for the added info. Perhaps, you potentially need to do more "event correlation" although the capacity testing will also help. You didn't actually state the frequency of the event (loss of voltage) and other things that might be associated with the event other than the fan speed which is some what expected... having said that... what speed was it running at before the "loss".

depending on the frequency, you might have to start monitoring the duty cycle wire coming from the PCM to the alternator... no fun, if the problem doesn't happen "predictably".
 
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Mike534x

Mike534x

Well-Known Member
#9
thanks for the added info. Perhaps, you potentially need to do more "event correlation" although the capacity testing will also help. You didn't actually state the frequency of the event (loss of voltage) and other things that might be associated with the event other than the fan speed which is some what expected... having said that... what speed was it running at before the "loss".

depending on the frequency, you might have to start monitoring the duty cycle wire coming from the PCM to the alternator... no fun, if the problem doesn't happen "predictably".
The loss happens at any of the fan speed settings, aside from that if the A/C is off there is no loss or fluctuation. Once it's on I start seeing it happen. It's sporadic but frequent. Once it's running and getting cold it'll do it, I haven't actually timed it but I want to say it's every 5-10 minutes roughly. As soon as I hit the off button for the A/C everything seems to be normal again.
 

budwich

Well-Known Member
#10
you need to try to correlate with other events... like your ac clutch cycling as opposed to "the ac was on".... engine events, power requiring events, turning lights on / off, manually changing fans, etc. Further, respect to monitoring some electrical, there are three wires going to your alternator, battery, duty and on/off. It is maybe the on/off one that is an issue since it appears voltage drops to battery voltage as opposed to nothing and further you don't get any dash lights indicating a charge problem.
 
#11
@Mooseman Was the SARVC available on the 05 model years?
I don't think so. I went with the info in your profile which says 2008 Envoy Denali.
 
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Mike534x

Mike534x

Well-Known Member
#12
@Mooseman Ahh ok. That's weird, I'm not sure how it switched to 08 on my profile. But yeah I do not see the module so I assume it's probably controlled by the alternator or PCM?

@budwich I tried monitoring to see if the drop is in response to the clutch cycling and it does not seem to sync with each other. Flipping the lights, messing with other electronics seems have no effect on it. I can be cruising at a steady speed on the highway and see it dip, or at a stop light with no change in RPM. All I have running during these events is the radio and the DTRL and of course the A/C. If it is the on/off wire could it be a matter of it needing to be reseated or cleaned to see if that changes how it behaves?
 
#13
You're saying 11.5-12V. Is this read via gauge on dash, or a multimeter? Reason being, if you're seeing true voltage drop down that low, you've got issues, as your battery should never let it drop that low unless it is bad, or you have a bad connection to it causing a voltage drop between your measuring point and the battery (i.e. a bad ground).

If you're going by the dash, I'd grab a meter you can watch somehow, and connect it to a solid voltage source (modified lighter plug maybe?) and see what it actually reads.

PCM controls the alternator output. That's why when you start up in the winter the alternator isn't charging for the first 10 seconds or so, then the PCM tells the alternator to start charging.

My 07 Silverado has the even more advanced stuff that actually drops the charge to naught but a trickle when the battery is charged and the load is low, supposedly to make the battery last longer by not overcharging. Looking at the battery replacement history on the truck, I'm not convinced it makes a hill of beans worth of a difference, but hey...
 

budwich

Well-Known Member
#14
@Mooseman Ahh ok. That's weird, I'm not sure how it switched to 08 on my profile. But yeah I do not see the module so I assume it's probably controlled by the alternator or PCM?

@budwich I tried monitoring to see if the drop is in response to the clutch cycling and it does not seem to sync with each other. Flipping the lights, messing with other electronics seems have no effect on it. I can be cruising at a steady speed on the highway and see it dip, or at a stop light with no change in RPM. All I have running during these events is the radio and the DTRL and of course the A/C. If it is the on/off wire could it be a matter of it needing to be reseated or cleaned to see if that changes how it behaves?
you could try checking the connector... the two controlling wires are a push in / on while the main power is a bolt on. Could be as simple as the pin not quite aligning well. It would be nice if you could see the issue more often (ie. few minutes of running) since you don't know the actual "trigger" beyond AC on. That way, if it happens more often the chances of having your meter hooked up to the wire and seeing it happen or not would be higher and a better diagnostic outcome. As far as the voltage drop, I think it is likely OK... maybe like going from a "loaded system" under alternator powering to a potentially "no alternator powering loaded system"... the battery won't likely hold up to say 12.6-.7... kind of like starting your vehicle... at not running, full charged battery will be over 12, but hit the starter and the battery will easily drop to 10.5-11 depending on its health, the health of the starter and a few other things.

My current guess would be if you see a voltage drop and no change in the on/off wire, then its an alternator out issue although then you would have to watch the duty cycle for a bit... ugh! If you see a change in the on/off at the same time, then you are looking at the ECM as a potential culprit. Might be one of the reasons why gm went to the SARVC as its cheaper to replace a standalone module than to do the ecm. :-(

Lastly, as suggested earlier, check your grounds... of course, it appears that the on/off is a ground signal sent to the alternator IF I understand GM schematics.

Last "throw up", the blower module may or may not "blow" because of the module itself... depending on what actually electrically happened to cause the heating. IF you have a bad ground, the motor may not be getting its "due power" and as result drawing more current than is necessary and thus causing heating in the module and thus if the heat causes contacts to burn which causes more heat and so the story goes.... :smile:
 
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#15
I've seen weird random voltage drops like that on my '02, just before the alternator crapped out. Get it checked.
 
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Mike534x

Mike534x

Well-Known Member
#16
@Sparky I'm hitting it with the multimeter this weekend to see if I can find anything. I just find it bizarre, if thats normal then its just another GM thing? I was mostly monitoring the voltage occurrences when this happens by watching the dash gauge (before using Torque). After doing more driving around today it looks like it drops more to the 12V range. I wonder if I can buy one of those cheap car charges, open it and run some wire to and leave it connected to the multi-meter and just drive around?

@budwich Yeah I really have no idea how to keep it as a replicating problem. The A/C seems to be the only thing that triggers it. It does not happen often enough at idle until I start driving with the A/C running, otherwise it performs normally with no abnormalities while driving. Well.....the A/C from time to time will blow a little warm, then cool, warm and then back to cool again. I suspect the fan clutch is at play here. I'll be checking out the grounds as well, and get some CRC cleaner for the connectors to see if it helps any. I tried searching the problem with the module down, there were a few users on the OS that had to replace it due to the same issue with the connector melting so I'm not sure if its directly connected to whats happening here.

@Mooseman I got the system tested today, everything came up normal. Battery shows "Good -Recharge" on the receipt. I think thats a bit low for a new battery unless thats normal? The alternator is factory original from the shape its in, I don't believe its ever been replaced compared to what was done to it before I purchased it. With 184k miles on it I'm just wondering if it would be a good idea to just go ahead and replace it anyway for good measure. I attached the receipt as well if anything stuck out. Not sure why it uploaded side ways.
 

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MRRSM

Lifetime VIP Supporter
#17
"Well.....the A/C from time to time will blow a little warm, then cool, warm and then back to cool again..."

Now THAT is a very interesting piece of information... especially if the A/C System is presently Over-Charged. What can happen in such situations is that if enough additional R-134A is introduced into the system beyond its weigh-in charge limit... it can flood the the Accumulator and allow Liquid Refrigerant to suddenly enter the Low Side Vapor Return Line that feeds right back into the A/C Compressor...and cause the problem of "Slugging the Compressor" ... since ALL Liquids are Incompressible.

The A/C Compressor is designed to compress Vapor Only ...and should any straight Liquid Coolant become ingested... the sudden Drag on the Scroll Pump internals would be horrendous... even if only momentary...and likewise drag down everything else as all Accessories are naturally being powered by the Crankshaft Harmonic Balancer Pulley via the Serpentine Belt.

Such a draw down of heavy resistance could certainly directly affect the performance of the Alternator...as the Liquid Slug passes through the A/C Compressor and the Engine RPM struggles to recover from this cyclic event. If this is the case... it is only a matter of time before the A/C Compressor has a seal failure... and its... Adios, Ice Cold Air.
 
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Mike534x

Mike534x

Well-Known Member
#18
@MRRSM It usually only does it when they truck is idling, especially for the first 5-8 minutes at start up and again after its warmed up and driven again. I bought a can of R-134A since I thought it was low on freon but the pressure gauge showed it was in the green.
 
#19
At that mileage, I would replace the alternator just to eliminate that as a possible source. It could be an intermittent issue and didn't manifest itself during the test.
 
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Mike534x

Mike534x

Well-Known Member
#20
@Mooseman I'm kind of wondering the same thing. I ordered a reman AC/Delco off of Amazon, hopefully this helps sort out the issue. Drove around for a bit with it fluctuating without the A/C running and could see the headlights dimming a bit (as well the gauge fluctuating). I figured it wouldn't hurt to run over to Firestone and have them test the battery themselves since its under warranty.
 

MRRSM

Lifetime VIP Supporter
#21
In a serendipitous Post made some time ago by "The Roadie" and recently refreshed by @Mooseman ...This Image shows a Four Ground Cluster on the Driver's Side of the Engine that might be worth hand-checking to see if any of these have loosened up if you can get your hand far enough down in the engine space to reach them:


THEROADIENGINEGROUNDIMAGE.jpg
 
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Mike534x

Mike534x

Well-Known Member
#22
In a serendipitous Post made some time ago by "The Roadie" and recently refreshed by @Mooseman ...This Image shows a Four Ground Cluster on the Driver's Side of the Engine that might be worth hand-checking to see if any of these have loosened up if you can get your hand far enough down in the engine space to reach them:


View attachment 85535
Thanks! but I don't believe it applies to my Envoy since I have the 5.3.
 

MRRSM

Lifetime VIP Supporter
#23
Ouch! (... Caught from Ambush... I see it now... down in your Sig-Line ) Sorry about that. Still... the Idea has merit... regardless of the engine block variations.
 
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Mike534x

Mike534x

Well-Known Member
#24
Ouch! (... Caught from Ambush... I see it now... down in your Sig-Line ) Sorry about that. Still... the Idea has merit... regardless of the engine block variations.
No problem! It stinks the V8 isn't nearly as document as the I6 haha. I'm trying to track down the ground location diagram like the I6, would that be located with one of the service manuals posted on the site? I replaced the alternator and still have the issue, so checking all wires and grounds are next on the list.

Though I'm noticing now that I keep Torque running when driving around to monitor everything, I see my idle on average is about 538-570, that's after its at operating temp. Seems a bit low, unless that's normal.


Small edit: After watching torque on the way home from work, I was able to see it drop to 11.5-12.3v. I saved the log file if its of any use.

Now if I were to replace the wiring, what kind of gauge would you all recommend? I assume its a good idea to replace the 3rd ground wire that leads to the fender?
 
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MRRSM

Lifetime VIP Supporter
#25
Well... the Lower RPM issue would certainly affect the performance and ability of the Alternator since it is actually an A/C Generator with Rectifiers to convert the Voltage Output to Direct Current. In addition to checking for the proper Ground Connections... I wonder if any of your CNP (Coil NEAR Plug) Coils would come under suspicion without the Optimal Voltage Output feeding from the Battery and being delivered 'with enough gusto' when the RPM dip below 600.

It might be worth your while to replace BOTH your AC Compressor and Serpentine Belts just in case the are engaging in any "Slipz-N-Grabz" and make for the surging affect as a result. If these two belts have never been changed out... it certainly will not hurt the future performance of the Engine AND the Air Conditioning System.
 

budwich

Well-Known Member
#26
It would appear that your "problem description" has "meandered" a bit. Now, it looks like there is a low idle speed which might be related to AC being on and caused by a "low idle issue" with a "dirty throttle body".
 
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Mike534x

Mike534x

Well-Known Member
#27
Well... the Lower RPM issue would certainly affect the performance and ability of the Alternator since it is actually an A/C Generator with Rectifiers to convert the Voltage Output to Direct Current. In addition to checking for the proper Ground Connections... I wonder if any of your CNP (Coil NEAR Plug) Coils would come under suspicion without the Optimal Voltage Output feeding from the Battery and being delivered 'with enough gusto' when the RPM dip below 600.

It might be worth your while to replace BOTH your AC Compressor and Serpentine Belts just in case the are engaging in any "Slipz-N-Grabz" and make for the surging affect as a result. If these two belts have never been changed out... it certainly will not hurt the future performance of the Engine AND the Air Conditioning System.
I'm sorry so would that be the spark plug wire, or the ignition coil thats mounted above the plugs?

Both belts were replaced last summer due to the old one squeaking every time it rained. I'm running Continental Elite's 4060922 and 4040365. What a pain in the rear to get that A/C belt on, took about an hour or too before it was all set.

@budwich I cleaned the throttle body last summer after replacing the air filter/clean the MAF sensor. It wasn't too dirty, but had some decent build up. After hooking everything back up it threw a CEL because of the idle being too high. I think it was hovering between 900-1,000 RPM, I did find a reset bulletin on the TBSS forum that told me how to go about resetting the PCM/re-learn the idle.
 

MRRSM

Lifetime VIP Supporter
#28
IIANM... The Wire/Coils might be packaged as a single unit to eliminate the loss of High Voltage coming out of the Coil. This is a very inexpensive Coil Spark Tester to quickly and innocuously test and ensure that all (8) of the Coils are throwing sufficiently potent High Voltage to keep the Spark Plugs working right:

https://www.amazon.com/dp/B0042KJV9U/?tag=gmtnation-20


 

budwich

Well-Known Member
#29
use the torque app to monitor your throttle position along with things like fuel trim levels. Not familiar with the v8 but a 4.2 below 600 rpm isn't good. However, from your description it is unclear whether you see the voltage drop during idle or at other times (highway speed).
 
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Mike534x

Mike534x

Well-Known Member
#30
@budwich Throttle position reads like 15-18% when at idle, roughly around that percentage. Fuel levels I'll be looking at as well, I need to try out @MRRSM ' suggestion of getting that coil tester. The drop happens at both idle and cruising speeds, though its easier to replicate at cruising speeds because it just happens if my foot is on the throttle or not. Somedays its sporadic, and some days its back to back. Its also easy to notice when the drop happens because of the air flowing from the vents slows down, and then picks back up when it recovers to the 13.8-14 range. After driving around all day with Torque connected I could see the digital counter drop between 11.5-12.3 and shoot back up to 14. We know its not the charging system, since there should be a warning going off and there isn't.

My list of things to check so far (thanks to all your suggestions) this weekend;

1. Ground connections/wires

2. Take truck over to Firestone for a load test/warranty the battery if needing to be replaced

3. Re-clean throttle body/intake and do a reset for the PCM to learn the throttle body perimeters again.

4. Take the throttle body off my Avalanche and swap into the Envoy and drive it around and see if the low idle still exists, or clears up with the swap. I was thinking the TPS would be the culprit, but there are no trouble codes or CEL lights illuminating the dash when this happens. But for the heck of it, I'll try the swap anyway, but I've never really seen the TB go bad before.

The last bit I don't know if it'll help at all but I figured since I'm cleaning the throttle body, might as well clean the MAF sensor and replace the air filter while I'm at it. Might grab a can of Seafoam top end engine cleaner and see if this could be a problem from carbon build up.

Or its just a small nuisance/oddity with this platform that I'll need to live with.
 

budwich

Well-Known Member
#31
The fact that you are seeing the voltage drops on torque shows that the PCM knows about the drop. However, it is not "automatic" that it will show a "charge error" indication.... so you can't rule out a "charging system issue" that easy. It also depending on what you mean by "charging system"... do you mean just the alternator or also the battery, the pcm along with any wiring?

one test you can do... measure the voltage on the "on / off" lead with the key on, engine off.
 
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MRRSM

Lifetime VIP Supporter
#32
Regarding your Question posed in Post # 24:

"...I'm trying to track down the ground location diagram like the I6, would that be located with one of the service manuals posted on the site?"

Yes. Check out this link and once you find and download the GM OEM Service Manual... eyeball the Index for Electrical Components...and a similar page with the information for the V-8 Engine Flavors will show the Ground Strap locations always referred to by the Alpha-Numeric of GXXX:

https://gmtnation.com/forums/threads/need-service-manuals-get-them-here.361/

Don't forget to Give Props and Thanks to @Mooseman for taking the time and effort to build such an Amazing GM Reference Library. :>)
 
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Mike534x

Mike534x

Well-Known Member
#33
@MRRSM Thanks for the link! I located the ground wires. I didn't see any kind of chaffing, there is some minor oxidation, and I cleaned the areas as best as I could where everything grounds. The issue is still there unfortunately.

Small-medium update

Drove around for a bit last night and while sitting at the stop light windows rolled down, the headlights started to dim (and of course the gauge dropping and torque showing it fell to around 12v). Picked back up soon after. I pulled into the supermarket, ran inside, not even 10 minutes, came out and started the truck to the headlights dim and as if the battery was drained. Worked ont he truck a bit today and took care of small things (cleaned the MAF sensor, new air filter etc). Throttle body wasn't too dirty so I didn't bother to yank it and clean it or anything.

Now a new issue has appeared with it wanting to stall, or it will stall if you give the engine a bit of gas while its idling. Stopped over at the part store to have everything retested and the battery came up that it was low, just like the first test. Otherwise it showed the new (well reman) alternator passed. I'm beginning to wonder if the battery has a weak cell and its just not showing up on the tests? or what are the odds its the alternator? or both. I feel like the more I look into this, the more of a "domino" effect is happening. Though I am wondering if maybe the throttle body itself could be an issue.

I did not hook up the multimeter up to the alternator or battery yet, did some cleaning in the garage earlier this summer and I forgot where it got crammed into.
 
#34
If you can, stick the battery on a charger for a while them get it tested. The fact it keeps coming back as low needing charged has me suspicious of it.
 
#35
What's your idle like? Should be ~650. I'd still give the throttle body a good cleaning and reset the PCM by disconnecting the battery for 30 minutes. I'd also charge up the battery.

If the battery had a bad cell, you would see a steady issue with voltage, not random drops.

I doubt the reman would exhibit the same issues but anything is possible. Try loading it down by turning on everything, especially the rear defrost, blower, A/C and lights. Listen to it and see if it does the usual steady whine of it working. Try the windows as that seems to trigger weirdness. See if the idle stays steady at 650.
 

I_Shoot_Back

Well-Known Member
#36
My 02 trailblazer did the intermittent 13.5volt to 11.5volt for awhile,mostly while driving but also at idle,just random. Turned out the single thin wire connector on the alternator wasen't making good contact. Took it apart,cleaned it and squeezed it a bit for a better fit and hasen't failed since.
 

MRRSM

Lifetime VIP Supporter
#37
@budwich 's Question still remains a viable issue to seriously consider attending. When you mention in passing that " I cleaned the Throttle Body...Last Summer..." Do you have a clear idea as to just how many miles have been put on the SUV since then?

The only way to eliminate the Throttle Body from this "Electrical Gremlin FUBAR Bucket List" is to actually take it off of the vehicle and perform an objective examination of the device... inside and out ...and carefully clean the thing to a Fair Thee Well with Carburettor Spray and not Brake Cleaner,

You must be careful NOT to fiddle around with the Baffle-Butterfly by pushing it in too aggressively or pulling on either. The Electric Drive Motor High Ratio Gear Box is subject to having teeth stripped or damaged and skip if you are not very careful.

I have been turning wrenches for over 50 Years.... so I've been around long enough to know that purchasing anything that has either been "Re-Built", "Re-Furbished" or "Re-Manufactured" to save money... invariably found me standing at the Parts Counters more times than I care to remember... looking down at Countermen with my "Thousand Yard Stare" while they swallowed hard at what I was about to tell them concerning all three of these "OEM? ...NOT" Failed Components they sold to me on one occasion or another.

Of all the Vehicles on the Planet... The GMT360s sometimes deserve to have the few extra dollars needed for OEM Quality Components laid down on the Counter Top in anticipation that buying anything less will simply not perform up to snuff. The Alternator is just such a component.
 

mrwitty_1

Well-Known Member
#38
I had the problem of battery always showing low when tested with the small test units. If you had the doors opened for any length of time the truck would not start, on occasions truck would fail to start or crank slow. When I tested it on a carbon pile load tester the battery was definitely no good. Replaced the battery and the truck ran much better. Suggest having it tested with a real battery tester.
 
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Mike534x

Mike534x

Well-Known Member
#39
If you can, stick the battery on a charger for a while them get it tested. The fact it keeps coming back as low needing charged has me suspicious of it.
That's why I keep wondering if its the battery or not. It showed low before the new alternator and now with it. I suppose it could be anything.

What's your idle like? Should be ~650. I'd still give the throttle body a good cleaning and reset the PCM by disconnecting the battery for 30 minutes. I'd also charge up the battery.

If the battery had a bad cell, you would see a steady issue with voltage, not random drops.

I doubt the reman would exhibit the same issues but anything is possible. Try loading it down by turning on everything, especially the rear defrost, blower, A/C and lights. Listen to it and see if it does the usual steady whine of it working. Try the windows as that seems to trigger weirdness. See if the idle stays steady at 650.
My idle reported by Torque is about 535-560. The needle on the dash is off by 100 rpm ever since my cluster was rebuilt, so instead of being above 500, its like a hair or too under. Everything else reports fine. If it helps, I can post the video I recorded earlier showing how it behaves when I give it gas at idle? Hitting both the driver and passenger window switches is enough to cause the voltage to tank on the truck. I do hear the whine from the alternator when running everything. Turning the A/C on is probably the only thing keeping it from stalling. Torque shows engine idling to hold between 565-580 with the A/C running. When I did the cleaning, the idle was stuck at 900-1,000 (last summer). It stayed high enough to cause the engine light to pop on and give me a code for excessive high idle. I googled the code and came across the TB SS forum where there was a GM bulletin listed on how to correct the issue, and after following the instructions the idle always seemed a little lower since then. I'm wondering if I should do the reset and instead of following the steps in the bulletin, just drive it around for a few days and let it learn on its own.

My 02 trailblazer did the intermittent 13.5volt to 11.5volt for awhile,mostly while driving but also at idle,just random. Turned out the single thin wire connector on the alternator wasen't making good contact. Took it apart,cleaned it and squeezed it a bit for a better fit and hasen't failed since.
I cleaned that one too, and its making as much contact as possible haha. Even hit the connector at the top of the alternator with some CRC electrical cleaner to see if it wasn't make much contact due to dirt.


@budwich 's Question still remains a viable issue to seriously consider attending. When you mention in passing that " I cleaned the Throttle Body...Last Summer..." Do you have a clear idea as to just how many miles have been put on the SUV since then?

The only way to eliminate the Throttle Body from this "Electrical Gremlin FUBAR Bucket List" is to actually take it off of the vehicle and perform an objective examination of the device... inside and out ...and carefully clean the thing to a Fair Thee Well with Carburettor Spray and not Brake Cleaner,

You must be careful NOT to fiddle around with the Baffle-Butterfly by pushing it in too aggressively or pulling on either. The Electric Drive Motor High Ratio Gear Box is subject to having teeth stripped or damaged and skip if you are not very careful.

I have been turning wrenches for over 50 Years.... so I've been around long enough to know that purchasing anything that has either been "Re-Built", "Re-Furbished" or "Re-Manufactured" to save money... invariably found me standing at the Parts Counters more times than I care to remember... looking down at Countermen with my "Thousand Yard Stare" while they swallowed hard at what I was about to tell them concerning all three of these "OEM? ...NOT" Failed Components they sold to me on one occasion or another.

Of all the Vehicles on the Planet... The GMT360s sometimes deserve to have the few extra dollars needed for OEM Quality Components laid down on the Counter Top in anticipation that buying anything less will simply not perform up to snuff. The Alternator is just such a component.
Its been about 8,000 miles since I cleaned it last summer. I'm just wondering if I should allow the PCM to reset, and drive it around so it can relearn on its own. The throttle body/PCM seem to be a bit more temperamental then the I6. After the first cleaning, it was stuck idling at 900-1,000 RPM. Which was enough to set off the check engine light indicating an extended condition of high idle. After doing searching, I came across a TB SS forum that had a tech bulletin from GM with the same engine code I had pop up with steps on how to get the PCM to calibrate itself by letting it idle for "x" amount of minutes and a few key on/off cycles. I'm almost positive I was delicate with it the first time around. I used CRC Throttle body cleaner, there was not much build up, but enough to create a black ring but no where near as coated as it was originally. I never really had an issue with refurb AC/Delco components in the past so I figured I was somewhat in the clear. I'll try another reset, I did notice the idle was a tad bit lower after the first round of cleaning which is making me wonder if the PCM did not relearn it like I originally thought last summer.

I had the problem of battery always showing low when tested with the small test units. If you had the doors opened for any length of time the truck would not start, on occasions truck would fail to start or crank slow. When I tested it on a carbon pile load tester the battery was definitely no good. Replaced the battery and the truck ran much better. Suggest having it tested with a real battery tester.
There is an Interstate Battery Center not too far from me, I was gonna hop over there Monday morning and have them do a proper test on the battery.
 
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OK everybody, we have to stop suggesting cleaning the throttle body because this is a V8 and, unlike the I6, cleaning it has little to no effect. Because of the overall prevalence of the I6, we tend to forget the V8, especially since I have one myself.
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I'll try another reset, I did notice the idle was a tad bit lower after the first round of cleaning which is making me wonder if the PCM did not relearn it like I originally thought last summer.
That is a good idea. Idle speed should be between 600-650. Despite having GM-SI and AllData, I can't find the exact spec. I found this video regarding a relearn for the throttle body. Try that after disconnecting the battery for 30 minutes.


After that, if the idle is still wonky, I'd be checking for vacuum leaks and the fuel trims.

There is an Interstate Battery Center not too far from me, I was gonna hop over there Monday morning and have them do a proper test on the battery.
That is also a good idea.
 

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