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Codes P0740, P0753, P0785, P1860?

Tiny
EARL91
  • MEMBER
  • 2000 CHEVROLET TAHOE
  • 180,000 MILES
I have the vehicle listed above Z71 5.7L. Codes P0740, p0753, p0785, p1860. It has a transmission in it that was refurbished 2 years ago. I installed a new create motor about a month ago. I check shift solenoid A and B. Both are working and receiving between 20 and 25 olm's about 21.7 to be exact. What are some things I can do to fix? Working on a budget.
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Tuesday, April 25th, 2023 AT 4:31 PM

17 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,081 POSTS
Here is information on the codes:

P0740: Torque Converter Clutch Circuit Malfunction.

P0753: Shift Solenoid A Electrical Malfunction.

P0785: Shift/Timing Solenoid Malfunction.

P1860: TCC PWM Solenoid Circuit Electrical Malfunction.

I would start by checking the electrical connector at the transmission. If that looks okay, I would install a rebuilt valve body. Check out the images (below). Please let us know what happens. Also, how is the fluid condition, is it burnt or low?
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Thursday, April 27th, 2023 AT 10:17 AM
Tiny
EARL91
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The fluid is good. I dropped the pain and checked the shift solenoids, and they were good. I cleaned everything while I was there. Changed the filter and put new fluid in. Do you think putting a new harness in would fix my problem? I have done a little research and it seems that that could possibly fix it.
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Friday, April 28th, 2023 AT 6:30 AM
Tiny
KEN L
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Yes, if the wiring is bad, it will cause this problem. Here is a guide to help you test the wiring with the transmission wiring diagrams below:

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

Check out the images (below). Please let us know what happens.
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Saturday, April 29th, 2023 AT 11:21 AM
Tiny
EARL91
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The valves in the valve body moved easily. So, I don't think it's that. That why I asked about harness. Thank you for the info. I will let you know how it goes.
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Sunday, April 30th, 2023 AT 7:49 AM
Tiny
KEN L
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Please do, have a great day.
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Sunday, April 30th, 2023 AT 10:52 AM
Tiny
EARL91
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  • 79 POSTS
I replaced the harness in the transmission. The truck can move better. I don't have to almost floor it to move. But the codes are still there after clearing them with the scanner. Also still can't feel or hear the truck shift. What would the next step be?
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Friday, May 12th, 2023 AT 10:56 AM
Tiny
KEN L
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I would install a rebuilt valve body, or you could have a bad PCM. How is the fluid condition?

This guide can help:

https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid

Please go over this guide and get back to us.

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Saturday, May 13th, 2023 AT 10:05 AM
Tiny
EARL91
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Can a bad ignition switch cause these shifting problems? My tachometer and speedometer on my cluster stopped working. And then all these problems started.
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Thursday, May 18th, 2023 AT 5:36 AM
Tiny
KEN L
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Yes, it could, here is how to change the switch out in the images below. Check out the images (below). Please let us know what happens.
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Thursday, May 18th, 2023 AT 12:25 PM
Tiny
EARL91
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Ignition switch did not.
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Sunday, May 28th, 2023 AT 8:57 AM
Tiny
KEN L
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It seems like it is the valve body or the wiring, did all of these codes come in only after you changed the transmission out?
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Tuesday, May 30th, 2023 AT 9:20 AM
Tiny
EARL91
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Okay. So, I bought this truck. The motor was locked up. It blew the cylinder walls out. So, I put a new motor in. The transmission was rebuilt about two years ago. It was all running good for about two weeks then all of the codes appeared. I have changed the internal harness. All new solenoids, new filter. And ignition switch. The only thing I haven't changed is the valve body and pump.
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Thursday, June 1st, 2023 AT 5:40 AM
Tiny
EARL91
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I'm also going to check my converter make sure it's not loose.
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Thursday, June 1st, 2023 AT 5:41 AM
Tiny
EARL91
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Any way you could send me all wiring diagrams for my transmission?
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Thursday, June 1st, 2023 AT 8:41 AM
Tiny
KEN L
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They are in the post above, click to enlarge in the images.
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Friday, June 2nd, 2023 AT 8:19 AM
Tiny
EARL91
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  • 79 POSTS
Could the gauge cluster not working cause my no shift issue?
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Thursday, July 13th, 2023 AT 1:41 PM
Tiny
KEN L
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So, the speedometer is not working? If so, this can be the problem, I would swap out the VSS sensor. Check out the images (below). Please let us know how it goes.
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Friday, July 14th, 2023 AT 8:57 AM

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