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Discussion Starter #43
Pin 73 appears to be quite big.

Going to make the time to pull my harness and check out what if anything going on in this area for my truck.

That picture identifies the middle socket as J2 which would match up w C2
 

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Discussion Starter #44
Minor discepancies: G105- left side near EBCM, G106- right side behind air cleaner.
Good catch. That chart was directly copied and pasted from the service manual. I guess their perspective on left and right was looking into engine compartment from bumper.
 

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From the 2005 GM Service Manual? Someone formatting automotive tech manuals doesn't know left from right? Well, maybe. After all, this is 'merica. Yesterday the eye doctor was looking in my right eye for a foreign object after I told him it was the left eye.
 

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Discussion Starter #46
Not sure if I had progress today or not.

I disconnected the ground right next to where dipstick enters the block. I attempted to clean the block in that location but w the front axle and stuff I really could not effectively clean that area.

I made a quick jumper wire to connect all three of the grounds there on the block and then up to the negative terminal on the battery.

I still ended up having a fluctuation in bolts and fan speed but not as bad as before. I only once had the dash error lights come on and I was much heavier on the throttle than normal.

If there was a ground problem there, I am not sure why the problem is not gone. But, it is certainly acting better.

Slightly happy but still confused.
 

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Well, I tapped out tonight. I bought a new truck and traded this colorado to the dealer. Good luck Ken and I wish you the best on your troubleshooting. A month of this was more than I had patience for. This morning it wouldn't start, Windows wouldn't go up or down and doors wouldn't lock. Finally started, went to work... When I got off work to go home the Windows and locks worked normally... Seriously... Strange happenings...

When I have to pop the hood open on my vehicle before I go to work, that was my limit.
 

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Discussion Starter #48
Congrats on the new truck, Mike.

Did you hide a note in the glovebox pointing to this thread for the new owner? :)
 

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Congrats on the new truck, Mike.

Did you hide a note in the glovebox pointing to this thread for the new owner? :)
Thanks Ken. New truck was going to happen one way or another. We had hoped to keep the Colorado and get the issue resolved but after the ordeal of not starting and the voodoo that happened yesterday we just said enough. I left no letter, but I suspect they will be long shortly on their own. During the drive to the dealer yesterday every time I'd hit a grade, the battery light would come on even though the engine RPMs were constant. I'd bet it is either that ground at the PCM or the PCM itself. That PCM gets very hot. I never did put my IR thermometer on it, but it was hotter than I'd think a computer should be.

My next step was going to be isolating the ground at pin 73 and then if nothing there, replace the PCM.

Again, good luck Ken. I'll keep subscribed to this thread and chime in if I think of anything to offer and to look for your final resolution. You will get it fixed.
 

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Discussion Starter #50 (Edited)
It seems the voltage measured at the battery is higher than I am seeing on the OBD2 port. My Tech2 was showing different voltages too. The battery voltage was in mid 15's measured directly on battery when OBD2 showed about 13.

OBD2 port gets voltage from the AUX Fuse 2 under the hood and is grounded to G300 under the driver's seat.

So, definitely a different ground point and voltage source from what the PCM monitors.

I'm wondering if the paint from when I replaced my engine last winter is blocking a good ground signal from something. Maybe once heated up, the painted surface is increasing in resistance and causing the problem.

The alternator grounds to the block due to it's contact w the block when it's bolted in place. I cannot remember if those mount points where the alternator mounts were stripped bare or left painted.

I am guessing that area of the block was painted. I'm used to a ground cable being attached to the alternator housing.

Over the upcoming extended weekend, I will pull the alternator and scuff the mount points.
 

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I was seeing 18 as reported by the OBD and directly at battery. I followed the voltage through the fuse box and all matched. I wonder if the OBD actually doesn't get the voltage at the OBD port instead it is read at the PCM and then encoded and sent on the datalink which is what the OBD is showing. That would be what I would expect. I cannot imagine the Tech2 is encoding the OBD V+ onboard and giving you that. It is possible, but I would think the voltage is being sent from the PCM with the rest of the data.

My money is still on either the ground at Pin 73 or a computer problem. I suspect it isn't the alternator grounding.
 

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Discussion Starter #52
The main way I have been monitoring the voltage is by Bluetooth adapter. I am pretty certain it monitors pin 16 of the port and not from the digital data stream.

I only played w the Tech2 one day. It's so big and bulky that it's not very easy to mess w while driving.

I did notice that it appeared to report a different value for voltage. I saw voltage reported under the BCM section, transmission and under engine. All multiple keystrokes from each other, so not at all real time monitoring of them concurrently.

I have not used the data logging via laptop w the Tech2. I guess I need to learn how to do that and possibly get some better real world data all in one file to review later.

It's one of the "clone" Tech2's. I haven't used it much since getting it. Maybe it's time to figure it out and have it pay for itself.
 

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Discussion Starter #53
I picked up a 500 amp carbon pile tester from HF. The battery and alternator both seem to pass the load test.

I also loaded up the alternator and then measured voltage between the negative battery terminal and the housing of the alternator. I figured if the alt was not grounding good to the block, I would see some buildup of voltage between the two. NOPE.

I did the same to the positive terminal and compared it to the volts between battery terminals. No difference.

Although today the temperature is a lot lower than the past few days. My weird electrical issues seem to be worse when it's hot outside.

I also checked terminal 73 on the PCM harness to chassis ground and had zero ohms.

I sprayed it with contact cleaner before reassembling the connection.

The hunt continues.
 

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Discussion Starter #54
On the drive in this morning I did not experience any issues.

Not sure if the removal and reinstall of the computer and alternator wiring harnesses did something or if it is just the lower temperature this morning.

Supposed to be mid 90's and high humidity on drive home this afternoon. That is the scenario that usually makes it the worst.
 

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On the drive in this morning I did not experience any issues.

Not sure if the removal and reinstall of the computer and alternator wiring harnesses did something or if it is just the lower temperature this morning.

Supposed to be mid 90's and high humidity on drive home this afternoon. That is the scenario that usually makes it the worst.
I've been following this thread and I'm glad to see you keep posting updates. Your findings could really help someone else down the road. :thumbup2:
 

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Ken,
I still think that the alternator is the cause of your electrical issues. It has a p.c. Board internal that controls your voltage. I would apply some heat when on the bench testing it. I think you have been so involved chasing electrical gremlins, it’s easy to over look what you have been chasing.
 

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Discussion Starter #57 (Edited)
Ken,
I still think that the alternator is the cause of your electrical issues. It has a p.c. Board internal that controls your voltage. I would apply some heat when on the bench testing it. I think you have been so involved chasing electrical gremlins, it’s easy to over look what you have been chasing.
Thanks for input.

My first thought was alternator, which is why I had it tested. I know the two auto parts places don't have the greatest testers, but the results came back good. That is why I got the carbon pile tester to put a better load on the alternator.

The price locally was about $250 on the alternator. If it was cheaper, I would just swap it... But u can't throw away that much $ when the tests I have done say it's good.

Also, I cannot think of a way that engine loading would cause the alternator to change it's output voltage. If the alt was bad, I think it would fairly consistently output a bad voltage. Me mashing on the gas pedal would not directly change anything in the alt to drive up the output voltage. Once again, the alt output is not varying w engine speed, but how much load I am putting on the Engine.

Are you sure there is a PC board in the alternator? From what I have read, all the voltage regulator control stuff is from the PCM.

I like the heat gun idea. It definitely seems heat related, but on the really hot days when it is acting up, I haven't had the time to get to a shop to have alt tested. I am not sure I can test anything on a bench, though. I would need to spin it and then apply the two signals from the PCM to simulate it being in the truck.

I guess I should find a shop that can do a bench test and take them my alternator.
 

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This info is from the 2005 GM Service Manual:

Generator:

The AD-244 generator is non-repairable. They are electrically similar to earlier models. The generator(s) feature the following major components:
• The delta stator
• The rectifier bridge
• The rotor with slip rings and brushes
• A conventional pulley
• Dual internal fans
• A voltage regulator

The pulley and the fan cool the slip ring and the frame.

The AD stands for Air-cooled Dual internal fan; the 2 is an electrical design designator; the 44 denotes the outside diameter of the stator laminations in millimeters, over 100 millimeters. The generator is rated at 150 amperes.

The generator features permanently lubricated bearings. Service should only include the tightening of mounting components. Otherwise, the generator is replaced as a complete unit.

Regulator:

The voltage regulator controls the field current of the rotor in order to limit system voltage. The regulator switches the current on and off at a rate of 400 cycles per second in order to perform the following functions:
• Radio noise control
• Obtain the correct average current needed for proper system voltage control

At high speeds, the on-time may be 10 percent with the off-time at 90 percent. At low speeds, the on-time may be 90 percent and the off-time 10 percent
 

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Discussion Starter #60
Still haven't figured it out.

This weekend I opened the wiring harness from the PCM to the underhood fuse block. I was hoping to find a splice for the PCM's ground wire.

The wiring goes under the radiator overflow bottle over the top of the front of the valve cover to the fuse block. After a lot of unwrapping, I discovered that it's a single wire w no splices.

The ground wire is the biggest wire in this harness. It also had a unique socket in the plug at the PCM. I couldn't figure out how to disassemble the plug at the PCM. I also did not have anything to check the tension or tightness of the pin and socket.

I'm still thinking it's this ground and the problem is w the connection at the PCM.

I just need to figure out how to open that connection or Break down and take it to dealer
 
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