Lost power while driving, now no crank no start?

2004 CHEVROLET TAHOE
250,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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SAUNDRA05
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While driving my vehicle listed above, no check engine light at all before this all happened, but it seems it lost power (A/C turned off, radio turned off, the system running through on dash saying to service 4wd, tire monitor sensors etc.,) although the engine did not turn off and I knew something was wrong so I stopped, put it in park and turned it off. I tried to start it but got nothing. It seems at the same time it drained the battery as we tried to jump it but did not get a crank or anything. This has been trial an error for over 2 weeks now.
I have since replaced the ignition switch twice. I replaced the starter relay, ignition relay. I had the starter and solenoid checked and they came back good (which is why I replaced the relays). We have checked all connections and get power. I swapped the PCM from another vehicle to see if that was the problem, still the same issues as before.
I am able to get it started by using a jumper wire where the starter relay goes. So, I did drive it to my nearest O'Reilly's Auto Parts store to have a diagnostic hooked up to see if any codes were going to be thrown. It wouldn't connect between the connector under the steering column and their handheld machine.
I don't know if it's important to say but It drove pretty rough on the way there and back. I could put the gas pedal to the floor, but it was very sluggish to get going and get up to any speed. I didn't try to make it go over 30MPH as a precaution to not make things worse. We can't figure out what is wrong and now I am at a loss for what else it could be.
Any help or advice would be greatly appreciated.
Oct 8, 2022 at 12:16 PM
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JACOBANDNICKOLAS
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Hi,

The description you mentioned when it all started sounded like the battery went dead. When this happened, by any chance did you notice if the alternator gauge was indicating it was charging?

There are several fuses that are tied into the starting circuit. Ignition fuse A and B in the under-hood fuse box, and ignition E and the crank fuse in the interior fuse box. Have you checked all of them? Also, when you checked them, did you confirm there is power to and from them? If not, do that.

Here is a link that explains how to do it:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Also, have you tried starting it in neutral? Is the anti-theft light staying on or flashing?

I attached the wiring schematic below, so you have a reference. Let me know as much as you can. For example, have you checked for power and ground at the starter relay?

Take care,

Joe

See pics below.
Images (Click to enlarge)
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Oct 8, 2022 at 10:10 PM
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SAUNDRA05
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All the fuses have been checked. All are getting power as far as starting. All the lights on my dash lit up. I've never had a check engine light on or anything before. When I stopped the car when this happened, I put it in neutral to see if it would start as well in park. I had little power inside, lights, seats could move. Eventually after trying and trying, the battery did give out.
I towed it to my parent's place and have been researching everything. I alternator is fine. The battery is even fine after I hooked it up to a charger. I was able to use it today to test the wiring under the fuse panel under the hood to make sure there was power leading from the PCM and vice versa as well as to check again everything I had already checked multiple times. No anti-theft light.
Weird thing is, I can run a jumper wire where starter relay is, and it will crank and turn over. I have gotten 2 of them as I thought the first one, I bought was bad. I took the PCM from a GMC Yukon and still nothing changed.
The starter relay was replaced as well. The ground is getting power. The cables are good to everything.
I have had the starter tested, starter solenoid tested as well as all the wiring connecting between, to and from.
I appreciate the wiring diagram. My father, my son and I have been looking at them since all this started over 2 weeks ago.
Oct 8, 2022 at 11:51 PM
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SAUNDRA05
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Also, if I didn't mention it in my first message, I did jump where the starter relay is with a wire and after it started, I reinstalled the starter relay and drove it to the local O'Reilly's to check for codes thrown as the check engine light was on, their machine couldn't read anything. No connection when they tried a few times. It was very sluggish to go from a stop. I don't know if that could tell you anything other than whatever caused this to happen made it that way.
Oct 9, 2022 at 12:01 AM
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JACOBANDNICKOLAS
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Hi,

If you have power and ground at the relay, then the only other things could be a weak connection or an open in the trigger wire between the relay and the starter. If you go to the starter, there is a purple wire. That wire should only have 12v when the key is in the start position. Have you checked for that?

Joe
Oct 9, 2022 at 4:13 PM
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SAUNDRA05
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Yes sir. That was checked and read exactly 12 volts. All wires, fuses, connections have been checked and all are getting power. The ground was replaced. There is power getting to everything. I am currently looking for a diagram of the wiring to the neutral safety switch. I don't think that is what it is, but I'd rather be safe than sorry. I'm very sorry if I am leaving anything out. We have done so much checking and rechecking and replacing switches and fuses and relays and then more testing as well as checking parts like the alternator, starter, solenoid etc. Finding what is wrong is getting more and more difficult and frustrating as time goes by.
Oct 9, 2022 at 4:35 PM
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JACOBANDNICKOLAS
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If you have power to everything, there has to be an open between the relay and the trigger wire on the starter.

If you look at the pics I attached above for the starter circuit, it also provides the wiring to the neutral safety switch. If you need something more detailed, let me know and I'll see if I can dig anything up for you.

Let me know.

Joe

PS: I just reread your last post. Do you mean you get 12v at the purple wire on the starter?
Oct 9, 2022 at 7:56 PM
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SAUNDRA05
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On mine the wire appears to be pink, but yes it was reading 12v.
Oct 14, 2022 at 1:21 PM
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JACOBANDNICKOLAS
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Hi,

If you are getting 12v on the purple wire at the starter, the starter itself is having an issue.

The 12v at the purple wire should only exist when the key is in the start position. If it does and you have 12v direct from the battery to the other terminal, it should work.

Let me know.

Joe
Oct 14, 2022 at 10:00 PM