FJ40 1974 Factory Wire Diagram? (1 Viewer)

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I'm trying to get my rear lights working. I also would like to attach the factory trailer socket and switch.
I think this is part of the problem with the lights not working.
I'm no electrician. First time doing this. Any help would be appreciated. Mahalo

QUESTION - Does anyone have a factory wire diagram for a 1974 FJ40? Or where to get one?

I looked at coolermans website and the schematics from the Haynes manual look close but they have extra colors.

Stock Wire Color Codes (from what I read on the forum)
G - Green = Park lights
GB - Green Black = Left Turn
GW - Green White = Brake Light
RB - Red Blue = Backup Lights
GY - Green Yellow = Right Turn/Brake/Emergency
GO - Green Orange = Left Turn/Brake/Emergency


1974 Haynes Schematics
****RL - Red Purple = I'm guessing this is Red Blue?
****GL - Green Purple = This connects between the Trailer socket and switch ONLY (Haynes Wire diagram)
****GR - Green Red = This connects between the Trailer socket and Passenger taillight ONLY (Haynes Wire diagram)
 
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I'm trying to get my rear lights working. I also would like to attach the factory trailer socket and switch.
I think this is part of the problem with the lights not working.
I'm no electrician. First time doing this. Any help would be appreciated. Mahalo

QUESTION - Does anyone have a factory wire diagram for a 1974 FJ40? Or where to get one?

I looked at coolermans website and the schematics from the Haynes manual look close but they have extra colors.

Stock Wire Color Codes (from what I read on the forum)
G - Green = Park lights
GB - Green Black = Left Turn
GW - Green White = Brake Light
RB - Red Blue = Backup Lights
GY - Green Yellow = Right Turn/Brake/Emergency
GO - Green Orange = Left Turn/Brake/Emergency


1974 Haynes Schematics
****RL - Red Purple = I'm guessing this is Red Blue?
****GL - Green Purple = This connects between the Trailer socket and switch ONLY (Haynes Wire diagram)
****GR - Green Red = This connects between the Trailer socket and Passenger taillight ONLY

20210301_212920.jpg
 
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I have that one just not sure if they made a mistake with some of the colors. Thanks for the help.

My confusion is:
My drivers side tail light harness plug has GB instead of Haynes GO
My passengers side tail light harness plug has GY instead of Haynes GR

The Haynes GO and GR go to the Trailer Switch (I have the trailer Switch and Plug)

My GB wire and GY wire from the tail light harnesses plug go to nothing.
I'm assuming they are suppose to go to the Trailer switch?

Also my GO comes from the harness and splices into 3.
1 wire goes to the drivers tail light with a factory female plug
1 wire is cut by the splice. I assume it goes to the passenger tail light
1 wire goes to the trailer socket area with a female plug

GO is not on the Haynes in this configuration
 
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Sorry, I lack electrical smarts :)
I would get a test light, hook up everything separately and test for continuity. Make sure the whole system works before i disect the harness/looms.
Hopefully some1 here can help you out...
 

73FJ40

After another night of rust removal!
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@KWA

An issue I discovered with the OEM rear wiring harness in my Jan 73 was that there were extra wires that were intended for the change to the "three color" rear combination lamps.

My truck still had the round, one color (red) combination rear stop lights. The circuits for that arrangement enables one filament in each lamp to be both a stop light and a blinker. I think the 74 models went to the red/amber/white light, which need an extra wire since the stop light circuit is separated from the blinker light.

So, my wiring harness had all of the wires listed in your "stock wire color codes" table I pasted below. I suspect that Toyota added the extra wires in anticipation of moving to the three color rear lights.

I found out that the GB and GW were not being used. My combination rear lamps used the GY and GO wires, and of course the G wire for the marker light.

One other question I would have is what signals Toyota was sending to the trailer hookup. Most trailers don't have the three color rear lights, so did Toyota have wires that would enable the truck to have the three color rear lights, but the trailer hookup was compatible with the single colored rear lights, with blinker and stop combined?

Stock Wire Color Codes (from what I read on the forum)
G - Green = Park lights
GB - Green Black = Left Turn
GW - Green White = Brake Light
RB - Red Blue = Backup Lights
GY - Green Yellow = Right Turn/Brake/Emergency
GO - Green Orange = Left Turn/Brake/Emergency
 
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So your 4 pin plugs have GY and GO?

I'm guessing the GO wire was extra in my harness. It goes to the drives side, passenger side, and middle.
Maybe a transition year like you said?

Just for reference and so I can think this through. I put what I have in my combination tail light 4 pin plugs.
I think I need to make a new post with the trailer and socket. I don't think it was hooked up right.
It looks like the Drivers GB and Passengers GY go back to the trailer socket/switch. But again are not hooked up right.
I also have a whole bunch of cut and half attached wires in the trailer socket/switch area.


My drivers side 4 pin plug for the combination lamps:
G - Also has a second Green wire coming out of harness plug for side light? (blue tape)
GW -
GB - From 4 pin plug goes back to trailer socket/switch area
RB -

OG - The one on the top with the factory female plug. Not hooked to the 4 pin plug.

FJ40 1974 Drivers Side Tail Light.jpeg


My passenger side 4 pin plug for the combination lamps:
G - After market splice for side marker light (blue tape)
GW -
GY - From 4 pin plug goes back to trailer socket/switch area
RB -

GO - Far right cut and goes back to harness.
FJ40 1974 Passenger Side Tail Light.jpeg
 

73FJ40

After another night of rust removal!
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@KWA
So your 4 pin plugs have GY and GO?

The single color (red) rear combination lamps did not have 4 pin plugs:

Drivers lamp 2.jpg


Driver rear lamp 1.jpg





You can see from the above pictures the original, standard arrangement for the older rear lamps. The only difference is that I added a W/B ground wire to the lamp housing, so I wouldn't have to grind off my fresh paint for the "factory ground path".

Those bullet connectors were all that were used in the lighting circuits throughout the truck on the lamp ends of the wiring harness. I replaced the original G/O wire on this side with the spiral striped wire illustrated.

In my original harness, there was a G/B wire hanging from the harness on this end that was not used. There was a G/W wire hanging from the passenger side harness that was not used. In the middle of the harness there were a number of female bullet connectors not in use, that I surmised were the intended connections for a trailer connection.

I assume that when the switch to the three color rear lamps was made, it was fairly easy to change connector terminals from barrel type to the 4 pin type that you have.
 
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