Neutral Safety Switch plug swap?

Tiny
MADIGHON
  • MEMBER
  • 1998 TOYOTA COROLLA
  • 1.8L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
We just swapped out the engine on my son’s car listed above with a used engine. Got everything in and making all the connections I found out that the wire harness on the used engine has 2 plugs down by the NSS. The old harness only had one black plug.

I found on another question they there are 2 options for this plug. The grey (as on the used harness) and the black (as on the old harness). Also saw that this is plug A2 and the other seems to be E1.

My question, how do I make this work? Can I cut out the grey connector and splice the black one in? What other options are there? Lastly, do I need to connect the second connector (E1) to anything?

Thanks a bunch.
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Saturday, March 1st, 2025 AT 10:39 PM

6 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,321 POSTS
Can I ask if the wiring colors to both plugs are the same? If so, then we can update the plug by slicing the wires. If not, it will be more complicated. Here are the wiring diagrams for the plug so we can see how it works. I see 6 wires going to the connector. Can you please confirm? Check out the images (below). Let us know how it goes.
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Monday, March 3rd, 2025 AT 10:42 AM
Tiny
MADIGHON
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  • 6 POSTS
It looks like there are 7 wires going into the grey plug on the replacement harness. There are only 5 wires going into the black plug on the old harness. I included 1 picture of the replacement and 2 pictures of the black plug to get both sides.

There is an extra blue wire on the replacement plug that isn't on the diagram you sent.

Also, based on the diagram, the other plug is an electronic controlled transmission solenoid plug. Why would my old harness not have that? Unless the replacement harness just doesn't have this plug going to the right location. I can check on that.
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Monday, March 3rd, 2025 AT 10:56 AM
Tiny
MADIGHON
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  • 6 POSTS
I've been doing more research. Our Corolla is a VE. This came with a 3-speed automatic transmission. The other versions came with a 4-speed automatic with O/D. The other versions also call out that they are Electronically controlled, but the 3 speed VE does not. Does this mean that the VE is controlled hydraulically and that I don't need to use the electronic controlled transmission solenoid plug?

Tag on Drivers doorway says the Transmission is 03A/A131L.

The wires on my plug are blue/black, red/blue, red/black, black/white and black. The 3rd picture is a better image of the wires. 4th picture is a wiring diagram from an online manual library. The black, black/white and red/black wires seem to match between this diagram and the one in the post above. It looks like the red blue in the diagram above is the wire I don’t need since this eventually goes to the overdrive and my model doesn’t have that. So now I need to figure out between the red/blue and the blue/black wires, which ones replace the light green/red (2) and the light green/black (L).

First picture is the 3 speed specs, the second is the 4 speed specs.
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Monday, March 3rd, 2025 AT 2:01 PM
Tiny
KEN L
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  • 50,321 POSTS
Yep, this can be a problem, I think you found the issue with different types of transmissions. You will need to follow the wiring the best you can to see if you can make it work. Here is a wiring diagram for the 3-speed so you can see how it works as well. Check out the images (below). Please let us know what happens.
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Tuesday, March 4th, 2025 AT 10:26 AM
Tiny
MADIGHON
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  • 6 POSTS
Thanks Ken,

Do you have access to diagrams of the plugs and pin locations at the ECM side of this? I have access to those plugs and can check continuity from one end to the other. So, if I can figure out which were 2 and L are located on those plugs, I could figure out which wire they are at the NSS end as well.
Thanks again.
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Tuesday, March 4th, 2025 AT 3:50 PM
Tiny
KEN L
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Here are the wiring diagrams of the transmission and the PCM. Check out the images (below). Let us know how it goes.
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Wednesday, March 5th, 2025 AT 9:11 AM

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