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Codes of P0740, P0758 and P1860, poor shifting and slipping?

Tiny
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  • MEMBER
  • 2005 CHEVROLET SILVERADO
  • 6.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 65,000 MILES
Did engine swap to 6.0l using 4l60e transmission. Did re-pin on harness using this guide: https://youtu.be/vZDXET1w1PY?si=SbLrY0crAHPXavOy. Have poor shifting, slipping and codes. Check connector and harness twice. Everything looks right. Perplexed. Please help.
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Monday, March 4th, 2024 AT 6:48 AM

12 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
I would double check the pin location. also, did you swap the PCM and complete wiring harness? Here is how the transmission should be wired. Here is a guide so you can check the wiring connections:

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

Check out the images (below). Please let us know what happens.
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Monday, March 4th, 2024 AT 11:01 AM
Tiny
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I checked the wiring and completed the wiring to the ECM. I did not swap out PCM. Is that inside the transmission?
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Monday, March 4th, 2024 AT 11:23 AM
Tiny
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Could there also be a mismatch of flex plate to converter? I did have to change out flywheel and remove spacer to ensure that the starter would match up.
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Monday, March 4th, 2024 AT 11:24 AM
Tiny
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Codes are 740, 758 and 1860.
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Monday, March 4th, 2024 AT 11:25 AM
Tiny
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The ECM was refreshed to the 6.0l. Also has a stage 1 cam.
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Monday, March 4th, 2024 AT 11:31 AM
Tiny
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The PCM is the same from the 4l60 just reminded at pins 42 and 79.
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Monday, March 4th, 2024 AT 11:42 AM
Tiny
KEN L
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Sorry its Monday! You included the codes my bad. Yes, the PCM is located next to the radiator.

P0740 - Torque Converter Clutch Circuit Malfunction:

P0758 - Shift Solenoid 'B' Electrical:

P1860 - TCC PWM Solenoid Circuit Electrical

So, the wiring looks like it might be incorrect. I would remove the transmission electrical connector so you can match the colors the wires going into and out of the main transmission connector. Here is the location of the PCM. Check out the images (below). Let us know what you find.
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Monday, March 4th, 2024 AT 11:53 AM
Tiny
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So, I did check out the wires yesterday at the tranny. Moved original pin S to U. Created new S pin to ECM pin 79 and new T pin to ECM pin 42.
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Monday, March 4th, 2024 AT 12:10 PM
Tiny
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That's how I wired it. Is that wrong?
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Monday, March 4th, 2024 AT 12:11 PM
Tiny
KEN L
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I am not sure how you wired it, I would double check the colors going into, and out of the main connector to make sure it matches the wiring diagrams I provided. Can I ask why you repinned it in the first place?
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Monday, March 4th, 2024 AT 12:16 PM
Tiny
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The harness is from the 6.0l and the transmission is a 4l60. Had to do the re pin from what I was told.
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Monday, March 4th, 2024 AT 12:19 PM
Tiny
KEN L
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I would try putting it back to the way it was.
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Tuesday, March 5th, 2024 AT 9:41 AM

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