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Hello All,

I have an 05 Trailblazer I have owned since 2006 and I had to replace the positive cable earlier this week. I took it on a long drive over good and poor dirt roads and decent paved roads with no problems and went home. About an hour later on a drive to the gas station, the battery light came on and the Voltage Meter on the dashboard dropped to approx. 12 volts which told me I was probably running on the battery only. Took it to O'Reilly Auto yesterday and they told me the Alternator was only putting out 11 volts. I took the alternator out and had them bench test and it was able to put out approx. 14.5 volts so not thinking it is the Alternator.

I went over all the wiring in the vehicle and ground is good at all expected spots, the positive cable from the alternator to the battery end rings good as well. I am concerned that the connector to the alternator from the PCM has a problem and I don't know where I can ring it out from on the PCM end to make sure I didn't break a wire while replacing the positive cable.

Does anyone have the wiring diagrams or suggestions? I saw in search results that there was a resources section at one point but I can't find it anywhere now.

Any help is greatly appreciated.
Try checking the
Hello All,

I have an 05 Trailblazer I have owned since 2006 and I had to replace the positive cable earlier this week. I took it on a long drive over good and poor dirt roads and decent paved roads with no problems and went home. About an hour later on a drive to the gas station, the battery light came on and the Voltage Meter on the dashboard dropped to approx. 12 volts which told me I was probably running on the battery only. Took it to O'Reilly Auto yesterday and they told me the Alternator was only putting out 11 volts. I took the alternator out and had them bench test and it was able to put out approx. 14.5 volts so not thinking it is the Alternator.

I went over all the wiring in the vehicle and ground is good at all expected spots, the positive cable from the alternator to the battery end rings good as well. I am concerned that the connector to the alternator from the PCM has a problem and I don't know where I can ring it out from on the PCM end to make sure I didn't break a wire while replacing the positive cable.

Does anyone have the wiring diagrams or suggestions? I saw in search results that there was a resources section at one point but I can't find it anywhere now.

Any help is greatly appreciated.
Have you checked the ground above the starter , on the motor block. If that鈥檚 ok , have the starter checked. It can do that. Then check continuity in the lines. Let me know 馃嵒
 

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Hello All,

I have an 05 Trailblazer I have owned since 2006 and I had to replace the positive cable earlier this week. I took it on a long drive over good and poor dirt roads and decent paved roads with no problems and went home. About an hour later on a drive to the gas station, the battery light came on and the Voltage Meter on the dashboard dropped to approx. 12 volts which told me I was probably running on the battery only. Took it to O'Reilly Auto yesterday and they told me the Alternator was only putting out 11 volts. I took the alternator out and had them bench test and it was able to put out approx. 14.5 volts so not thinking it is the Alternator.

I went over all the wiring in the vehicle and ground is good at all expected spots, the positive cable from the alternator to the battery end rings good as well. I am concerned that the connector to the alternator from the PCM has a problem and I don't know where I can ring it out from on the PCM end to make sure I didn't break a wire while replacing the positive cable.

Does anyone have the wiring diagrams or suggestions? I saw in search results that there was a resources section at one point but I can't find it anywhere now.

Any help is greatly appreciated.
If it has a sun roof check that out wiring in ceiling or underhood fuses could b poor condition under them.
 

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I should have qualified it. Given the substantial extra work of the front transaxle running thru the motor, it gives pause to those considering replacing a Trailblazer engine.
Yep I would just disconnected permanently, I fixed mine in the driveway. But if it happens again. I鈥檒l take the inner axles out and drive shaft and cap both ends. Done.
 

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Yep I would just disconnected permanently, I fixed mine in the driveway. But if it happens again. I鈥檒l take the inner axles out and drive shaft and cap both ends. Done.
I wouldn't mind having front axles taken out. A bonus in doing that, is the oil pan can be dropped which is necessary for timing chain repair. But the 4wd does have value when it's truly needed for traction.
 

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I wouldn't mind having front axles taken out. A bonus in doing that, is the oil pan can be dropped which is necessary for timing chain repair. But the 4wd does have value when it's truly needed for traction.
You don鈥檛 have to remove the pan , three things you can do , the two inner axles pull out,leave the outer axles in the hub, it keeps everything together. Brakes and Rotors. Take the boot off And clean the grease out of the end. Cap the entrance where the axle enters in the oil pan Then remove the small Drive shaft , next to the large Drive shaft. And that鈥檚 it, less work for the same results , make sure you do it right, it鈥檚 your life. Any questions come back on and ask before you tie it up.
 

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You don鈥檛 have to remove the pan , three things you can do , the two inner axles pull out,leave the outer axles in the hub, it keeps everything together. Brakes and Rotors. Take the boot off And clean the grease out of the end. Cap the entrance where the axle enters in the oil pan Then remove the small Drive shaft , next to the large Drive shaft. And that鈥檚 it, less work for the same results , make sure you do it right, it鈥檚 your life. Any questions come back on and ask before you tie it up.
Thanks for the info! I was misunderstood. What I meant by added bonus of removing front axles in addition to making engine removal easy, was that it also allows for oilpan to be dropped, which is a requirement for doing timing chain replacement.
 

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RE: This becomes professional stuff - stuff I don't do any more, but I DO know it has gotten a lot more serious and almost impossible for a DIYer any more.

^that's the point, they don't want people working on the cars. It's about making people pay up for service. Unfortunately with the frequently unreasonable costs involved, the opposite could result in people deciding to forego servicing altogether, resulting in pretty bad and worse outcomes in the future. A sad situation, indeed.
 

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RE: This becomes professional stuff - stuff I don't do any more, but I DO know it has gotten a lot more serious and almost impossible for a DIYer any more.

^that's the point, they don't want people working on the cars. It's about making people pay up for service. Unfortunately with the frequently unreasonable costs involved, the opposite could result in people deciding to forego servicing altogether, resulting in pretty bad and worse outcomes in the future. A sad situation, indeed.
I'm not 100% in the same mindset as you.

Vehicles are what they are because of what the consumers want ---->
  1. Mileage
  2. Performance
  3. Creature comfort
  4. Class/styling
  5. Prestige
When manufacturers have to thin down the wiring to save weight ... you know things get serious because DC gets "lost" over long distances and with thinner wire even moreso.

Computers, remote drivers, adaptive strategies, malfunction reporting and addressable memories with live stream testing capabilities, etc.,... all add complexity.

Putting self-testing modules out on the periphery of the vehicle ... far away from dependable voltage, subject to RMI or induced signals, further complicates matters .... all in the name of improving the herd.

Be honest here .... your dad's 1936 Oldsmobile got a new engine every 20,000 miles and maybe a "ring and valve job" somewhere in the middle.... there wasn't such a thing as a tune up. It was called a rebuild.

Clutches, synchros and u-joints were a never ending reality and wheel bearings failed all the time even when repacked ever 3,000 mile's or so.

Your car today can go 250,000 miles with minimal problems ...... unless it is neglected.

It emits vastly less dirty exhaust, burning much lower octane than the vehicles of just 40 years ago.
Oil changes aren't monthly.
Flat tires don't happen very often
Tires can last 50-60,000 miles.
Exhaust systems usually good for the life of the car........
You can drive in air conditioning or heat or any combination of them
Seats electrically adjust - some by memory ascertained by scanning the key fob on the ignition key.
6.1 stereo systems +
DVD and CD players with rear/remote screens
Low noise, with sound control for easily conversationally permissive interior materials
Heated seats, mirrors, rear window and even steering wheels!
Hands-free Cellphone-Bluetooth ability.
Wifi hotspot (for a stupidly giant fee)
Tires that tell you they are going flat or just need some air.....
When it's safe to change a lane,
To stop the vehicle even if the driver is distracted and keep collisions from happening in the firs6 TVt place.
Information centers, because!

And the new cars sacrifice themselves via air bags that not only sense a collision but can tell which airbags to inflate first and how fast, how hard to inflate them to save the vehicle's occupants.
They have crumble/crush zones and intelligent seatbelts to save the passengers from human stupidity.


Yup.... your daddy's Oldsmobile didn't do any of that!
 

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I agree cars can do much more, my point was basically that the electronics and mechanical of cars are increasingly difficult to understand without factory training. Im just lamenting on the fact that overcomplexity has made it an uphill battle for DIYers to understand and work their own cars. Purely as an example, look how much replacing push start FOBs cost, and which require dealer programming. Why can't we order traditional ignition if we want it???
 

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2004 chevy trailblazer_lt
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We've become a society that wants all the creature comforts but are unwilling to learn how to fix it ourselves when it malfunctions, and we believe it should be repaired for little or nothing because we've also become too darn cheap when it comes to paying other people to do jobs we used to do.

We also value our time much, much more that anyone else's time.

Hence the need for forums like this where those of us who can and desire to do things such as maintaining their own vehicles can share information and ask for assistance when we get stumped.
 

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I submit, when it comes to cars, it's not hard to see why we value our time, when we see the mechanics hourly rate is nearly $100 an hour.
 

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2005 chevy trailblazer_ls
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Discussion Starter #33
Hey All,

I finally have the time to debrief on this. The chain that led to me creating this post started with being semi ignorant in the large variety of ways to replace many of the components in your car. It did lead me to discover other potentially disastrous issues with the vehicle so I am net positive in the effort but I want to take the time to outline here what I did correctly and incorrectly in the after action review.

The TLDR of this is that the output from the alternator to the battery had shorted to ground and blew the fusible link in the battery cable so it had to be replaced. To be entertained or informed from my adventure, feel free to keep reading.

The initial problem was that the threads were stripped on the bolt connector to the battery on the positive cable. I assumed that the whole run had to be replaced and that you can't just simply replace the one bolt. It turns out as shown here that I was wrong and you can buy just the bolt. You can even purchase replacement sheaths after cutting the old one off to replace the bolt. So all my pain could have been avoided by just buying and installing a new bolt. That being said, here is the real adventure that resulted from my ignorance.

I ordered a new positive battery cable from Rock Auto and proceeded to install it in the vehicle while taking note of what went where and how. In the process of connecting the lead to the Starter Motor, the post came off the solenoid and caused many colorful words on my part. So a new starter had to be isntalled. After that was done I then completed the connections to the alternator, the fuse block, and the battery. I was careful to ring out all cable connections to ensure continuity from the end of each cable to the battery end. I didn't think or worry about checking for ground because I had taken the alternator out before during other repairs and thought I was pretty good at it. Little did I know what I had done wrong and frustration at continued failures led me to overlook my error until nearly the end. We will come back to that.

Side note, the vehicle had been offline for over a year due to other repairs. So I was a bit "done" with the whole thing and a little spun up.

When the alternator apparently failed to produce proper voltage after a very long drive to test my latest repair I hope you can understand why I wasn't happy and definitely not thinking properly. My first thought was that either the alternator was bad, it was brand new from those other repairs, or the PCM/ECM had failed which had been suspected during those other repairs as well. So i went down the rabbit hole noted here of how to test signals and connections from the alternator to the ECM and the battery and the whole adventure.

The alternator and the one that it had replaced were both bench tested and good, I falsely believed the cable from the alternator to the battery was also good because I had tested it during installation so that couldn't possibly be wrong. I took the wiring harness apart in the false belief a wire was broken somewhere due to my yanking harnesses while replacing the positive battery cable. Good thing on that as shown in the picture further up in the chain of this post. I did some testing for the signal from the ECM to the Alternator, side note on that, you can't get a signal if the connector isn't plugged in so back probe while the connector is on is the only way to check that. I tested for voltage at the battery from the Alternator just to make sure the voltage sensor wasn't bad and it wasn't.

This is where I finally started homing in on the cause of the original failure and what had to be fixed. You will love this. I decided to test at the Alternator both with the positive lead attached and detached. Someone claimed that testing with the lead off was bad for the alternator but I will cover that in this paragraph. While potentially hazardous to my own health, testing for voltage with the lead off was useless because there wasn't a load so the voltage regulator wasn't going to let any voltage show on the post anyway. Time to digress on basic electrical theory and the advanced safeguards available to us. Electricity cannot flow if the circuit isn't complete. Let me repeat that. Electricity cannot flow if the circuit is not complete. We have various devices in place to prevent the flow of electricity in an automobile when something goes wrong, the most visible of course being the fuses in the blocks. The others as noted in my research specific to this issue are the voltage regulator and the fusible link in the cable. Now that I have that out of the way, testing for voltage at the post on the Alternator is not hazardous to the device as there are defenses in place to prevent voltage flow when the positive connection to the battery from the alternator is lost. If you care to challenge this then riddle me the action of the vehicle when the fusible link goes out.

This is where we get to the meat of what I did wrong at first and what eventually had to be done. When putting the new cable on, I had the end of the cable bent too close to the metal hose clamp under the alternator and in doing so with all the vibrations of driving down the rough dirt roads I likely gave it the opportunity to short to vehicle ground even with the rubber protective boot over the post as the end of the clamp was sharp enough to pierce the boot. So my theory is that when that happened, the fusible link in the battery cable did its job and melted, thus taking the battery and the rest of the electrical system out of the path from the alternator and preventing more catastrophic damage and likely some unforgivable screaming on my part.

By this time, days in to the new frustration, I finally decided to test the cable from the alternator to the battery again and kept coming up with an open instead of a good link. Finally, I found the failure in the system and I was more annoyed because new cable and not knowing about the ability to just replace the side post bolt. It was obvious I needed to replace my brand new cable and a deadline set by wanting to go camping didn't allow for a new cable from Rock Auto and so I decided to cut the boot off the old cable to see what held all those cables together and determined I could swap the good bolt from the now bad cable to the good cable with the bad bolt. I will be happy to provide pictures of the cut boot and the cable without the boot on so you can see what I found.

Old cable in with new bolt and alternator and wiring harness put back together and it all came up and ran as it should. The moral of the story, when you think your alternator is bad, first check to make sure the cable is good from alternator to battery, then test for continuity between the alternator post and the vehicle ground if the cable is good, then test for signal from the ECM to the alternator, would have saved me days. But to note as well, my wrong assumptions did discover some severely damaged and corroded wires in the harness so net positive at the end.
 
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