Codes p1860, p1626, p0785, and p0740?

2000 CHEVROLET TAHOE
200,000 MILES • 5.7L • V8 • TURBO • 4WD • AUTOMATIC
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EARL91
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The vehicle listed above is a z71 old model. i just installed a brand-new rebuilt transmission. This is the second one in just a few months. when i clear the DTCs the noise it is making goes away for a few seconds. so, i know the transmission is good. its giving a p1860, p1626, p0785, p0740. please help.
Jan 29, 2024 at 6:02 AM
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Can you please shoot a quick video with your phone so I can hear the noise? That way I can tell for sure what's going on. You can upload it here with your response. We need to hear the noise, so we know which direction to go to help you fix the car. It takes time to upload so please be patient.

P1860 - TCC PWM Solenoid Circuit Electrical

P1626 - Theft Deterrent System Fuel Enable Circuit

P0785 - Shift/Timing Solenoid Malfunction

P0740 - Torque Converter Clutch Circuit Malfunction

With these codes I would check the electrical connector at the transmission make sure the connector is free from dirt and that it is in good shape and fully secured. If so then the problem is inside the transmission. I would get a rebuild valve body to install, if you know the transmission is good, I would replace the PCM with rebuilt unit but check the electrical connectors first. You can get a preprogrammed unit by searching Google or Ebay. Check out the images (below). Let us know how it goes.
Jan 29, 2024 at 10:40 AM
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EARL91
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If I clear the code. The sound goes away for a split second.
Jan 30, 2024 at 8:10 AM
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STRAILER
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Thanks for the video. if the codes come back that fast it is a hard code. How is the condition of the transmission electrical connector? Also did the vehicle have these codes before you started the repairs?
Jan 30, 2024 at 10:20 AM
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EARL91
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The connector condition is good. I cleaned them and checked. Nothing wrong there from what i can see. Yes, the truck did have the codes before the repair. I can't reset the tap with the scan tool. And I'm not sure how i could do a reset to see if that might fix it.
Jan 30, 2024 at 12:26 PM
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EARL91
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i had just found the wires leading to my distributor or all crushed and busted open. could this be a leading cause of my issue?
Jan 31, 2024 at 9:14 AM
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Yes, this can cause the problem, I would repair the wiring and then clear the codes again to see what happens.
Feb 1, 2024 at 11:31 AM
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EARL91
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No change.
Feb 4, 2024 at 9:58 AM
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STRAILER
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Okay, I would try the PCM then, let me know please.
Feb 5, 2024 at 10:35 AM
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EARL91
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I replaced the PCM no change. i have no idea what it could be. i hope they didn't send another transmission with issues.
still has p1860, p0758, p0753, and p0740.
Mar 5, 2024 at 12:26 PM
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EARL91
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where can i get a new wiring harness?
Mar 6, 2024 at 7:22 AM
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STRAILER
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I would try a wrecking yard, if the wiring is repaired then I would suspect the transmission is having an issue, did you have these codes before you started with the new transmission?
Mar 6, 2024 at 8:45 AM
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EARL91
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Yes, I did. This is the second transmission. First had forward gear engaged all time.
Mar 7, 2024 at 5:32 AM
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STRAILER
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I would try a new wiring harness if this has been the same problem with a different transmission. To be sure you can check the wiring by following this guide. You should be able to repair the wiring.

https://www.2carpros.com/articles/how-to-check-wiring

Here are the complete wiring diagrams so you can do the testing. Also, double check the fuses in the wiring diagrams for power with the key on. Check out the images (below). Let us know what you find.
Mar 7, 2024 at 9:50 AM
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EARL91
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So, my gauge cluster does not work. i know in certain vehicles that if the gauge cluster is bad, it will affect the transmission. Do you think this could be the issue?
Mar 9, 2024 at 6:30 AM
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STRAILER
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Yep, I have seen that as well, the cluster is a part of the CAN network.
Mar 10, 2024 at 10:54 AM
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EARL91
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So, I believe I am starting to narrow things down. Either it's the cluster, ignition switch or a speed sensor or bad connector. Or neutral safety switch. It honestly all that is left.
Mar 11, 2024 at 8:38 PM
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Did you check the wiring?
Mar 12, 2024 at 11:38 AM
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EARL91
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I have. I can't seem to find any alarming issues.
Mar 13, 2024 at 5:38 AM
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With these codes it will be inside the transmission the wiring or PCM which you say you have checked or replaced.
Mar 13, 2024 at 9:25 AM
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EARL91
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New PCM and new transmission.
Mar 13, 2024 at 9:27 AM
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It has to be in the wiring then.
Mar 13, 2024 at 10:31 AM
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EARL91
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I believe it's the wiring that goes to the VSS.
Mar 13, 2024 at 10:34 AM
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STRAILER
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Put the wiring through the tests in the guide that should help us see what's going on.
Mar 13, 2024 at 10:38 AM
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EARL91
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It was my gauge cluster. I punched it until it started working. I'm going to get another for when the one i have now goes out fully. Runs better that it has since i got it. Thank you for all your help.
Mar 20, 2024 at 8:39 AM
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Thanks for letting us know, we are here to help, please use 2CarPros anytime.
Mar 21, 2024 at 12:42 PM