Replaced Transmission and Neutral Safety Switch harnesses?

Tiny
OPTIMISITC13
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
Hello, So I got involved with putting in a transmission and replacing both wiring harnesses for neutral safety switch in which most of this was taken apart before I had touched the vehicle which I hate doing but was trying to help a friend out. However I put a used transmission in "reputable place for used parts" anyhow the wires on the new harness which one has 4 and the other harness for NSS is 7 as I only have a total of 10 wires and they are not oe color coated either so after putting everything in and together I can get vehicle to start but when putting into gear it doesn't matter which one the vehicle won't move as well as instrument gauges at least speedometer is at 80mph at idle and temp gauge is not even reading on gauge it's way passed the hot mark which is not overheating do to just starting vehicle my question is, can the neutral safety switch have anything to do with this? I am thinking it does but I have looked everywhere on how to wire both of them which I know the 4 wire is right that one was oe colored coated so I just matched wire for wire but the 7 pronged wire harness I have no idea if it's correct I am thinking not, hoping you can help please?
Thursday, July 20th, 2023 AT 9:11 PM

17 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,732 POSTS
It sounds like the wiring is not connected correctly. Here are the wiring diagrams and a guide to help test the connections to help you see if the wiring is working.

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

We also run the codes to see what comes up.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Check out the images (below). Please let us know what you find.
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Saturday, July 22nd, 2023 AT 11:28 AM
Tiny
OPTIMISITC13
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  • 11 POSTS
So, I am hoping you can help me out with this, and I hope this helps see attached image and can you advise me what wire should go where. As I have looked at the schematics and I am not exactly sure 100% where they should go however wiring is not my strongest suit just hoping you might be able to clarify this for me please?
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Saturday, July 22nd, 2023 AT 7:34 PM
Tiny
KEN L
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Can you remove the gear range sensor and install it on the new transmission? That would be best instead of trying to wire a switch that doesn't below in the truck. Check out the images (below). Please let us know what happens.
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Sunday, July 23rd, 2023 AT 2:37 PM
Tiny
OPTIMISITC13
  • MEMBER
  • 11 POSTS
I am trying to install the wiring harness that connects to the neutral safety switch. It doesn't matter if I put the new in and or the one that came off old transmission if I don't have a wire connector to plug into it, why would that matter? The picture I sent is the wire connector that I need to have, and the individual wires are the colors that I have that came off the wire harness. I just need to know what color go to what on wire connector as I seen diagram you posted, and I am not a 100% sure which one goes with what.
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Sunday, July 23rd, 2023 AT 7:32 PM
Tiny
OPTIMISITC13
  • MEMBER
  • 11 POSTS
The old wiring harness that plugs into the neutral safety switch has been damaged prior to me working on it therefore I had to buy a new harness.
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Sunday, July 23rd, 2023 AT 7:38 PM
Tiny
KEN L
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What year make model is the neutral safety switch are you trying to wire in? I can get the wiring diagrams for that part and that way we can compare.
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Monday, July 24th, 2023 AT 11:13 AM
Tiny
OPTIMISITC13
  • MEMBER
  • 11 POSTS
2003 Chevy Silverado 1500 5.3l 4wd.
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Monday, July 24th, 2023 AT 3:30 PM
Tiny
KEN L
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We already have the wiring diagrams for that model. What year did the neutral safety switch come out of you are trying to wire in?
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Tuesday, July 25th, 2023 AT 6:51 PM
Tiny
OPTIMISITC13
  • MEMBER
  • 11 POSTS
2003 Chevy Silverado 5.3l 4wd its brand new I bought an OEM part.
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Tuesday, July 25th, 2023 AT 6:55 PM
Tiny
KEN L
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Sorry I am getting confused, so the NSS is for the same vehicle, so the wiring matches or doesn't not match? The writing on the image is too small to read.
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Thursday, July 27th, 2023 AT 1:17 PM
Tiny
OPTIMISITC13
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  • 11 POSTS
The wiring harness does not match the wiring to the truck so I'm confused on what wire goes with what? The harness is for the this vehicle but because it is aftermarket the wires do not match.
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Thursday, July 27th, 2023 AT 3:33 PM
Tiny
OPTIMISITC13
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We are speaking of the same thing right the transmission range sensor aka neutral safety switch, correct?
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Thursday, July 27th, 2023 AT 3:36 PM
Tiny
KEN L
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Yes, the neutral safety switch, that is what the wiring diagrams are for. I don't have any information on an aftermarket harness.
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Friday, July 28th, 2023 AT 10:11 AM
Tiny
OPTIMISITC13
  • MEMBER
  • 11 POSTS
So A, B, C, D, E, F, and G on the wiring harness won't be the same as the original harness? I thought the location identified as the above letters is all that mattered am I wrong? Meaning a certain color wire goes to A, B, C etc, etc?
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Friday, July 28th, 2023 AT 2:44 PM
Tiny
OPTIMISITC13
  • MEMBER
  • 11 POSTS
Because the lettering on the original switch are the exact same on the aftermarket harness. Can you tell me based on your wiring diagram what color wire is supposed to go to what location on the wiring harness?
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Friday, July 28th, 2023 AT 2:46 PM
Tiny
OPTIMISITC13
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This is the best I can get it I hope you can tell me what wire goes to what location on harness.
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Friday, July 28th, 2023 AT 3:22 PM
Tiny
KEN L
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Gotcha, here is the information you need to finish the job. Check out the images (below). Please let us know what happens.
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Saturday, July 29th, 2023 AT 12:35 PM

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