Trailer wiring loom

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

buzz also make sure you have a good earth. Lots of issues with trailer lights are down to poor earth. The main relay box is in the back in the jack compartment (usually).

[buzzdog Lurker Find all posts View Profile Close buzzdog]

buzz also make sure you have a good earth. Lots of issues with trailer lights are down to poor earth. The main relay box is in the back in the jack compartment (usually).

I did notice the big white wire when I opened up the prado socket and according to the socket diagram, this is the earth. There was a little corrosion on the screw but not that much? It's all cleaned up now but it still exhibits the anomaly, really weird?
I was sure it was the socket as I've done a bit of dirt road driving down to the Roper and various other remote fishing areas, so was kinda bummed when the issue didn't resolve itself.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Are you using the flat style of plug or round? I used to have connection problems with the round plugs, particularly after two weeks camping at the beach. Since converting to flat plugs the problems have all but gone away. Sometimes L or R indicator lights play up but that is usually when someone has been ham fisted with the plug and a quick poke with a flat blade screwdriver has it all working again. I am running LED lights on the trailer and that helps a lot too.

[buzzdog Lurker Find all posts View Profile Close buzzdog]

Are you using the flat style of plug or round? I used to have connection problems with the round plugs, particularly after two weeks camping at the beach. Since converting to flat plugs the problems have all but gone away. Sometimes L or R indicator lights play up but that is usually when someone has been ham fisted with the plug and a quick poke with a flat blade screwdriver has it all working again. I am running LED lights on the trailer and that helps a lot too.

The flat style one.
I have taken the prado and my boat down some corrugated and dirt roads on my way to some remote fishing spots, so I guess something may have wriggled loose?

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Doesn't hurt to pull the plugs off, clean the bare ends and connectors and put it all back together.

[buzzdog Lurker Find all posts View Profile Close buzzdog]

Doesn't hurt to pull the plugs off, clean the bare ends and connectors and put it all back together.

G'day mjrandom,
Yeah, have give the connections a clean on both the socket and the plug. Did a test with the prado; turned the headlights on and indicated left, both the indicator and brake lights are working as they should. So I guess the issue along the wiring loom somewhere?

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Test the signal at the plug that at least will tell you if the problem is in the trailer wiring or Prado wiring. Nothing for it but to keep looking. Good luck.

[buzzdog Lurker Find all posts View Profile Close buzzdog]

Test the signal at the plug that at least will tell you if the problem is in the trailer wiring or Prado wiring. Nothing for it but to keep looking. Good luck.

Will do, it'll probably be something really small and insignificant.

[dagree Member Find all posts View Profile Close dagree]

I did notice the big white wire when I opened up the prado socket and according to the socket diagram, this is the earth. There was a little corrosion on the screw but not that much? It's all cleaned up now but it still exhibits the anomaly, really weird?
I was sure it was the socket as I've done a bit of dirt road driving down to the Roper and various other remote fishing areas, so was kinda bummed when the issue didn't resolve itself.

I would also check any earth connections on the lights themselves.

[Arthur Veturis Lurker Find all posts View Profile Close Arthur Veturis]

I lost my vehicle's trailer socket last week. Must have been on some rocks in the river...:shock: All thats left is the plate and just a 4 core cable dangling with illogical wiring (? Not sure what the previous owner or his "autoelectrician" friend was up to Clearly inadequate for a trailer and highly illegal...)

Anyway, I obviously now need to discard this heath-robinson cable and properly rewire a new socket to the vehicle harnes with a 7 core cable. The vehicle harness connector in the jack compartment of the Prado 120 has been bastardised but there are 6 wires at the vehicle harness. See attached image:



There is:

Green
Blue/Black
Green/Yellow
Grey
Red/Black
Blue/Yellow

The Haynes Repair Manual says (page 12-24): "Identify the wires...", so will obviously have to do that, I suppose. But has anyone maybe wired a trailer for a Prado 120 and know which wire is which? It will help a lot! Thanks.

[Arthur Veturis Lurker Find all posts View Profile Close Arthur Veturis]

Sorted it out this afternoon. Tested each wire with a 12V light bulb tester (worked like a charm! ) and matched each up to the standard 7 pin arrangement:

1 = Blue/Black (Left Indicator);
4 = Blue/Yellow (Right Indicator);
5+7 = Green (Left+Right Taillights wired together);
6 = Green/Yellow (Stop)
Red: Unknown/ Grey: Unknown (One of these must be the brakes?... The other auxilary/ for caravan lighting?)

So, turns out you could indeed use a 4 core cable!

[dixon Lurker Find all posts View Profile Close dixon]

Does anyone know the 6 Pin plug pin outs for the trailer tow harness? I been trying to connect my tow harness and when the lights turn on - the indicators are reversed. Left blinks right and right blinks left. And the Stop lamps blink as well. Freaking confused.
But if the head lights are off.. the left and right blinkers are fine?

What are the exact pin outs - HELP from anyone appreciated !

[dixon Lurker Find all posts View Profile Close dixon]

Sorted it out this afternoon. Tested each wire with a 12V light bulb tester (worked like a charm! ) and matched each up to the standard 7 pin arrangement:

1 = Blue/Black (Left Indicator);
4 = Blue/Yellow (Right Indicator);
5+7 = Green (Left+Right Taillights wired together);
6 = Green/Yellow (Stop)
Red: Unknown/ Grey: Unknown (One of these must be the brakes?... The other auxilary/ for caravan lighting?)

So, turns out you could indeed use a 4 core cable!

Hi - The 5 is normally Electric Brakes - isn't it ? What is Green Left and Right Tail lights together mean ? Is that a Y split cable meaning Green to #5 and #7 ?

[dixon Lurker Find all posts View Profile Close dixon]

Tow Harness Causes Blinking Lights and Wrong Signals

I lost my vehicle's trailer socket last week. Must have been on some rocks in the river...:shock: All thats left is the plate and just a 4 core cable dangling with illogical wiring (? Not sure what the previous owner or his "autoelectrician" friend was up to Clearly inadequate for a trailer and highly illegal...)

Anyway, I obviously now need to discard this heath-robinson cable and properly rewire a new socket to the vehicle harnes with a 7 core cable. The vehicle harness connector in the jack compartment of the Prado 120 has been bastardised but there are 6 wires at the vehicle harness. See attached image:

[ATTACH=CONFIG]15133[/ATTACH]

There is:

Green
Blue/Black
Green/Yellow
Grey
Red/Black
Blue/Yellow

The Haynes Repair Manual says (page 12-24): "Identify the wires...", so will obviously have to do that, I suppose. But has anyone maybe wired a trailer for a Prado 120 and know which wire is which? It will help a lot! Thanks.

I have come to the conclusion that manually wiring a harness to the cables - as above colour codes are 100 % correct. However... there are inherited errors with signals being wrong even though the cables seem right. It is because of a relay or ECU (Electronic Control Unit) missing. There are different voltages through the wiring system - control blinking and stop signals. There is NO way that you can connect a wiring harness straight from the shop and splice it to make it work.

I found the answer at www.towbarsaustralia.com.au / faq section.

(Electronic Control Unit) or (ECM – Electronic Control Module) * * * HERE IT IS * * *

Vehicles since the 1980`s have been fitted with Can-bus or Multiplexing wiring, a system designed to cut down on the amount of wiring required in a motor vehicle, to save weight, improve fuel economy as-well as to capitalise on new technologies making vehicles more user friendly with improved creature comforts and of course safety. This vehicle wiring system uses a series of electronic control units (ECU`s) to control various aspects within the vehicle.

When another electronic component is required to be added to this arrangement it can cause issues if not installed correctly. The vehicle’s ECU`s can basically get confused and send out warnings to the vehicle that there is confusion. Therefore, when adding a trailer connection harness to a vehicle an additional electrical component or ECU may be required. This can be done in one of two ways.

No. 1 Directly incorporated into the Can-bus system.

An additional ECU can be incorporated directly into the Can-bus system so it will communicate with the other ECU`s hence turning off reverse sensors / camera`s and modifying ABS, traction control and stability systems. This installation is normally carried out by the vehicle manufacturer at the time of genuine towbar fitment. It is time consuming and can be expensive as existing on-board ECU’s may need reprogramming to accommodate the towbar installation.

No. 2 Connection via a Bypass / Intelligent ECU.

A Bypass ECU (Intelligent ECU) is simply attached to the vehicle’s rear light wiring harness and takes a signal from the harness telling the Bypass ECU when the vehicle is indicating, braking or the lights are turned on. This type of ECU draws little current and therefore causes no issues for the Can-bus system.

Certain ECUs can detect the different voltages sent on a shared wire circuit (sometimes vehicle manufacturers will use a brake and tail light signal through one single wire especially with LED lights) and therefore can determine how the output signal is sent to the trailer.

As the Bypass ECU has its own separate power source it can safely send the correct signals to the trailer connection plug wiring without any issues or effect to the vehicle’s other sensitive circuits.


Hope this helps !

[GMnJM Lurker Find all posts View Profile Close GMnJM]

Hello Ghost, I am really grateful for your contribution to this thread. Your picture of the trailer indicator fuse solved my problem quick as a flash. Thanks to this I am up and running again.

GMnJM