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Discussion Starter · #1 ·
First, I'm new here so I hope this is in the right spot.
I have a 04 Chevy trailblazer ext, it's a great truck. Bought it last may and did a whole host of repairs on it
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Right now I'm chasing the batt draw, and am confused. I hook up my meter on amps to ground post then ground cable. I get a reading of 4.76 but then in like maybe 30 seconds before I can start removing fuses the meter goes to 0.00. What would cause that? Any help would be appreciated.
 

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'05 Chevy TB EXT
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QUIT DISCONNECTING THE BATTERY FOR YOUR AMUSEMENT.

YOU ARE CAUSING ALL SORTS OF PROBLEMS WHICH ARE SPENDY ($$$$) AND HARD TO REPAIR.

MODERN VEHICLES HAVE LOTS OF COMPUTERS AND PROCESSORS THAT "GO TO SLEEP" IN A SPECIFIC ORDER.

WHAT YOU ARE SEEING IS A FEW OF THEM HOLDING ON UNTIL IT'S THEIR TURN TO TAKE A NAP.
IF THEY DON'T GET THEIR NAP --- FLYING MONKEYS ARE GONNA COME OUT OF THE GLOVE COMPARTMENT TO INVADE YOUR HOUSE.​

IT'S NORMAL --- QUIT IT!!!!!
 

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'05 Chevy TB EXT
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You're looking in the wrong place.

If you use YT as your proctor --- you may not be getting the good stuff --- if it's on the internet, it is suspect unless it obeys serendipitous logic flow.

There should ALWAYS be a small draw (and possibly a spark) when you reconnect the battery ... but disconnecting the battery is, in the first place --- WRONG.

Whomever is doing that and showing it as a diagnostic procedure or that a spark is not correct, is wrong ... totally and unequivocally wrong. Walk away from such fools.

But I will leave you to your YouTube diagnosticians --- happy trails!

I shan't compete with their logic and your assumptions any further.
 

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Discussion Starter · #5 ·
Along the same line I have a question.
My instrument panel has 2 gages that don't work, the gas and batt gage, and batt light is usually dimly lit. I imagine it's bad step motors in the instrument panel. Could that be causing the draw?
If I don't start it everyday, in 2 days I'll have to jump it, so I know there's something up.
I ended up leaving a FB group cuz they kept saying watch a video.
 

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'05 Chevy TB EXT
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You've come here, hat in hand after following YT and yet you want to present that misinformation as a possibility.

When the key's OFF - so are the stepper motors on the dash.

You sound like you've quit listening to ill-informed boobs and that's good --- so-o-o-o you came here when YT failed you ... yet you want to argue?

Like I told you the last time --- and THIS IS the last time --- I'm outta here with you.
 

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2004 chevy trailblazer_lt
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3,007 Posts
allen410 - Welcome to the Forum!

Also, allen410 - accept it, you were led astray by the youtube videos in so many different ways. Now, if you really want assistance in helping you figure out what is wrong with your TrailBlazer, then you are going to first, admit to yourself that you were given erroneous information on youtube. Second, you are going to have to learn how to diagnose problems on modern vehicles, and third, you are going to need to purchase a couple of necessary tools (which are actually quite inexpensive compared to the cost of unnecessarily replacing one or two functioning properly parts). Third, you are going to have to put up with our questions because you are there, we are not, and we cannot magically see your TrailBlazer, and what you are doing to it, so we tend to ask some very specific questions in order to keep from sending you down the wrong diagnostics branch, and we might even ask for a picture or two.

OK, now for the required tools. If you do not already own them, you will need a decent Digital Multimeter (DMM) and a decent code reader/live data scanner. If you have an android device, then this combination of a Bluetooth OBDII dongle and Torque Pro app is hard to beat, and it costs less than $25.00 ($5.00 for the Torque Pro app, and anywhere from $12 - $20 for the dongle on Amazon). Here is the link to the Bluetooth Dongle (which currently sells for $13.99):


Now here is why you should never, ever disconnect the battery for routine diagnostics:

DO NOT DISCONNECT THE BATTERY - REMOVE THE APPROPRIATE FUSE(S). Why? Because when you reconnect the battery, the HVAC actuators inside of the dash are commanded to run a recalibration procedure which stresses the old brittle plastic gears inside the actuators and the brittle plastic gears break and leaves you unable to control where the air comes out, or control the temperature of the air, etc. Replacing at least one of them literally requires the removal of the entire dash! So, if you ever need to actually disconnect the battery, such as in the case of needing to install a new battery, be sure and use some kind of Keep Memory Alive device to avoid the HVAC actuator recalibration routine.

Now a couple of things.

One, when you do a parasitic draw test, you have to wait about 30 minutes before you begin reading the amount of current in Amperes (or milliamperes) being drawn from the battery. Why? Because all of the computer modules do not go to sleep the moment you shut the engine off.

Two, to measure parasitic draw, you put the multimeter into current mode and then you put the DMM in series with a battery cable. You do not measure current or voltage going from a vehicle ground to the battery unless you are doing a voltage drop test or are looking to create some fireworks with an exploding battery (when the DMM is in current mode). When you do this, remember to hook up a KAM device in parallel with the DMM until all the modules go to sleep.

So now, starting at the beginning, how may we help you (and please do not forget any OBDII codes you are aware of)?
 

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Discussion Starter · #9 ·
Lol, thank you for the nice reply.
This is the first vehicle I've had that is so electronic. This truck was sitting for 3 years in a garage when I bought it. I had to pull headliner and remove big mouse nest and under hood I had to repair some chewed wires. I've replaced the alternator and batt last year. 2 gages don't work, gas and batt. There are no obd codes, the damn thing runs like a champ.
The thing is when I leave it sit for a day or two if barely starts. I've measured the volts with my dmm and it's been at 10.5v. Hence I started the whole yt adventure.
While I am a retired mechanic, electrical stuff has always been my nemesis.
 

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2004 chevy trailblazer_lt
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3,007 Posts
OK, now we are on to something! The first thing you have to realize about this vehicle is that everything is controlled by a computer module of one kind or another. The Engine Control Module (or Powertrain Control Module) (ECMor PCM) covers the engine and partially the transmission. Then there is the Body Control Module (BCM) which controls the interior and exterior lights, the door open chime, the seat belt chime, the radio, the HVAC, etc. (it's a long list). Then there is the liftgate module often referred to as the read BCM.

Now, in order for the TrailBlazer to run properly, it must have good clean voltage in the range of 12.2 to 14.0 VDC (give or take a little). AC ripple out of the alternator must be 20 mV or less otherwise it will mess with the electronics. Electrical connectors must be fully seated and tight and clean. Grounds are super important and they must also be clean and tight. Battery cables need to be free of the green grunge disease, and unless you really want problems, please heed the following:

(I know I put this in earlier, but it needs to be stated over and over)
DO NOT DISCONNECT THE BATTERY - REMOVE THE APPROPRIATE FUSE(S). Why? Because when you reconnect the battery, the HVAC actuators inside of the dash are commanded to run a recalibration procedure which stresses the old brittle plastic gears inside the actuators and the brittle plastic gears break and leaves you unable to control where the air comes out, or control the temperature of the air, etc. Replacing at least one of them literally requires the removal of the entire dash! So, if you ever need to actually disconnect the battery, such as in the case of needing to install a new battery, be sure and use some kind of Keep Memory Alive device to avoid the HVAC actuator recalibration routine.

Now, I am not a pro, but I've been repairing cars since the mid 1970s and about the only thing I am hesitant to mess with is an automatic transmission. I'll rebuild Rochester Quadrajets all day long, but other than doing an AT fluid and filter change, I don't mess with transmissions.

Now a couple of random goodies before I forget. There is an important ground in the passenger compartment and it's located under the carpet immediately to the right of the gas pedal where the foot rests. For some reason, it loosens up and corrodes and when it does, it causes havoc. The alternator is controlled by the ECM. Weird unexplainable electrical gremlins such as the windows going down on their own, the radio changing stations by itself, the clock in the radio resetting randomly, dash lights misbehaving, etc., point to an ignition switch going bad. With the ignition switches, it is not a matter of if it will go bad, it's a matter of when it will go bad.

Well, since rodents have been having a feast on your TrailBlazer, I fear you are going to have to endure some nightmarish things for awhile as you track various things down. Now, if you have a high parasitic current drain, the first thing I would do is to pull the fuse for the OnStar module. I'm sorry but I don't know which fuse that is, but I do know you can download a copy of the owners manual from the GM website.

I do have a copy of the factory service manual in pdf form and it is broken up into sections. If you want one, you can download it from the GMTNation website. Here is the direct link: Need service manuals? Get them here!

Make sure your alternator is putting out adequate voltage and current, get a load test on the battery just to make sure it does not have a bad cell.

Good Luck and please don't be shy!
 

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2003 chevy trailblazer_ltz
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My instrument panel has 2 gages that don't work, the gas and batt gage, and batt light is usually dimly lit. I imagine it's bad step motors in the instrument panel. Could that be causing the draw?
If I don't start it everyday, in 2 days I'll have to jump it, so I know there's something up.
If this were in MY driveway, I'd pull the instrument cluster to replace ALL the stepper motors. Replace the soldered-in light bulbs at the same time.

The "Batt" light is dimly lit. Probably means the alternator is not charging properly. Perhaps failed diodes limiting output current. I'm tempted to say that's where your parasitic draw is...except your meter is telling you there is no parasitic draw after about thirty seconds.

Have the battery load tested. I put a Mexican Optima in my '03 Trailblazer, and had a dead battery every month. Charge it overnight, good for another month. Changed alternator, changed starter (preventative maintenance at that mileage, they had no indication of failure) cleaned the battery cable ends, and the battery went dead the next month. Replaced battery...haven't had a problem since.
 

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Discussion Starter · #12 ·
Lol, my hands are too big for those little step motor parts. That and I'm not confident enough in soldering on a circuit board. i'll be sending my inst panel out to someone.
i spent the morning cleaning grounds under the hood, theres a lot of them. i popped off the 2 caps on top of the battery where the acid goes and noticed 1 cell was low in acid, so i will be getting it looad tested.
 

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OK, now we are on to something! The first thing you have to realize about this vehicle is that everything is controlled by a computer module of one kind or another. The Engine Control Module (or Powertrain Control Module) (ECMor PCM) covers the engine and partially the transmission. Then there is the Body Control Module (BCM) which controls the interior and exterior lights, the door open chime, the seat belt chime, the radio, the HVAC, etc. (it's a long list). Then there is the liftgate module often referred to as the read BCM.

Now, in order for the TrailBlazer to run properly, it must have good clean voltage in the range of 12.2 to 14.0 VDC (give or take a little). AC ripple out of the alternator must be 20 mV or less otherwise it will mess with the electronics. Electrical connectors must be fully seated and tight and clean. Grounds are super important and they must also be clean and tight. Battery cables need to be free of the green grunge disease, and unless you really want problems, please heed the following:

(I know I put this in earlier, but it needs to be stated over and over)
DO NOT DISCONNECT THE BATTERY - REMOVE THE APPROPRIATE FUSE(S). Why? Because when you reconnect the battery, the HVAC actuators inside of the dash are commanded to run a recalibration procedure which stresses the old brittle plastic gears inside the actuators and the brittle plastic gears break and leaves you unable to control where the air comes out, or control the temperature of the air, etc. Replacing at least one of them literally requires the removal of the entire dash! So, if you ever need to actually disconnect the battery, such as in the case of needing to install a new battery, be sure and use some kind of Keep Memory Alive device to avoid the HVAC actuator recalibration routine.

Now, I am not a pro, but I've been repairing cars since the mid 1970s and about the only thing I am hesitant to mess with is an automatic transmission. I'll rebuild Rochester Quadrajets all day long, but other than doing an AT fluid and filter change, I don't mess with transmissions.

Now a couple of random goodies before I forget. There is an important ground in the passenger compartment and it's located under the carpet immediately to the right of the gas pedal where the foot rests. For some reason, it loosens up and corrodes and when it does, it causes havoc. The alternator is controlled by the ECM. Weird unexplainable electrical gremlins such as the windows going down on their own, the radio changing stations by itself, the clock in the radio resetting randomly, dash lights misbehaving, etc., point to an ignition switch going bad. With the ignition switches, it is not a matter of if it will go bad, it's a matter of when it will go bad.

Well, since rodents have been having a feast on your TrailBlazer, I fear you are going to have to endure some nightmarish things for awhile as you track various things down. Now, if you have a high parasitic current drain, the first thing I would do is to pull the fuse for the OnStar module. I'm sorry but I don't know which fuse that is, but I do know you can download a copy of the owners manual from the GM website.

I do have a copy of the factory service manual in pdf form and it is broken up into sections. If you want one, you can download it from the GMTNation website. Here is the direct link: Need service manuals? Get them here!

Make sure your alternator is putting out adequate voltage and current, get a load test on the battery just to make sure it does not have a bad cell.

Good Luck and please don't be shy!
The fuse for the Onstar module was the cause for my drain. On my 2008 it is a 15A fuse in the fusebox under the driver side passenger seat.
 

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Discussion Starter · #14 ·
Yeah thanks, I actually disabled that a few days ago.
Just got my battery tested today and it's junk, so I'll be bringing that back to Walmart. I got it last August. Still pulling alternator and getting it tested as well, got that from advance auto parts last winter.
 

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2004 Trailblazer LS 4x4, 4.2L:, 2016 ATS-V, 2014 CTS-V Wagon, 2018 Audi A7
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I just changed my less than one year old battery this weekend. It was toast. Unfortunately I was unable to exchange it as I was in the middle of BuFu so I took the financial hit. She now runs great! Moral of the story is that 'new' batteries do go bad, sometimes quickly.
 

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Just got my battery tested today and it's junk, so I'll be bringing that back to Walmart. I got it last August. Still pulling alternator and getting it tested as well, got that from advance auto parts last winter.
I just changed my less than one year old battery this weekend. It was toast... ...She now runs great! Moral of the story is that 'new' batteries do go bad, sometimes quickly.
Yes, batteries "can" go bad quickly.

I would be wondering what caused the battery failure--how did the alternator and starter test? The charge light was glowing dimly; is that fixed? Problems with the wire harness that connects battery, starter, and alternator?
 

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In my case the battery/truck sat at the repair shop for six weeks. It doesn't get run often as it is my "cabin truck". I always leave it on a trickle charge when I am gone. Always.
 

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04 Envoy, 200k+ miles
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OK, now we are on to something! The first thing you have to realize about this vehicle is that everything is controlled by a computer module of one kind or another. The Engine Control Module (or Powertrain Control Module) (ECMor PCM) covers the engine and partially the transmission. Then there is the Body Control Module (BCM) which controls the interior and exterior lights, the door open chime, the seat belt chime, the radio, the HVAC, etc. (it's a long list). Then there is the liftgate module often referred to as the read BCM.

Now, in order for the TrailBlazer to run properly, it must have good clean voltage in the range of 12.2 to 14.0 VDC (give or take a little). AC ripple out of the alternator must be 20 mV or less otherwise it will mess with the electronics. Electrical connectors must be fully seated and tight and clean. Grounds are super important and they must also be clean and tight. Battery cables need to be free of the green grunge disease, and unless you really want problems, please heed the following:

(I know I put this in earlier, but it needs to be stated over and over)
DO NOT DISCONNECT THE BATTERY - REMOVE THE APPROPRIATE FUSE(S). Why? Because when you reconnect the battery, the HVAC actuators inside of the dash are commanded to run a recalibration procedure which stresses the old brittle plastic gears inside the actuators and the brittle plastic gears break and leaves you unable to control where the air comes out, or control the temperature of the air, etc. Replacing at least one of them literally requires the removal of the entire dash! So, if you ever need to actually disconnect the battery, such as in the case of needing to install a new battery, be sure and use some kind of Keep Memory Alive device to avoid the HVAC actuator recalibration routine.

Now, I am not a pro, but I've been repairing cars since the mid 1970s and about the only thing I am hesitant to mess with is an automatic transmission. I'll rebuild Rochester Quadrajets all day long, but other than doing an AT fluid and filter change, I don't mess with transmissions.

Now a couple of random goodies before I forget. There is an important ground in the passenger compartment and it's located under the carpet immediately to the right of the gas pedal where the foot rests. For some reason, it loosens up and corrodes and when it does, it causes havoc. The alternator is controlled by the ECM. Weird unexplainable electrical gremlins such as the windows going down on their own, the radio changing stations by itself, the clock in the radio resetting randomly, dash lights misbehaving, etc., point to an ignition switch going bad. With the ignition switches, it is not a matter of if it will go bad, it's a matter of when it will go bad.

Well, since rodents have been having a feast on your TrailBlazer, I fear you are going to have to endure some nightmarish things for awhile as you track various things down. Now, if you have a high parasitic current drain, the first thing I would do is to pull the fuse for the OnStar module. I'm sorry but I don't know which fuse that is, but I do know you can download a copy of the owners manual from the GM website.

I do have a copy of the factory service manual in pdf form and it is broken up into sections. If you want one, you can download it from the GMTNation website. Here is the direct link: Need service manuals? Get them here!

Make sure your alternator is putting out adequate voltage and current, get a load test on the battery just to make sure it does not have a bad cell.

Good Luck and please don't be shy!
Chem_Man, Thanks for the awesome links from Mooseman/GMTNation!
 
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