I have a Toyota Camry 2004. When I just bought it, I have noticed that it has a tow ball. I didn't really intend to use it but now it could really help me to move few things around with a trailer I can borrow from a friend. The thing is that when I started connecting it to a car, I have realized that there is no electricity outlet for the trailer (the one used for powering the lights on the trailer) so I didn't have any place to stuck the trailer's plug to... I was really surprised since I was sure that if there is a tow ball - there must be a power outlet. I guess I was wrong here. So what I wanted to ask is:

  1. Maybe I am looking in the wrong place? I have scanned all the back of the car and tried to feel it with my hand hiding below the car. I have even looked in the trunk. No luck.
  2. If there is no such plug after all, is it possible to install one?
  3. If IT IS possible to install it, can it be a DIY project or this is strictly professional business?

2 Answers 2


Many older cars with a tow ball had no electrical outlet - back in the day regulations weren't as strict on adding lights to trailers etc.

Many modern cars either have an outlet, or have a factory option for adding one. Typically, Camry's from about 97 or 98 have a panel you need to remove inside the trunk. This does vary a bit between versions, but this video is pretty typical. Check your manufacturers guide for details. Definitely do-able yourself with a little bit of DIY experience.

The very newest cars actually have setup options which not only give you electrics for the lights but also alter ECU settings to cope with the added mass behind the car. This should make life even easier, but typically is safer as a factory modification.

  • 1
    Hi and thanks a lot for your answer! Actually my Camry is 2004 so I guess it should have been there. And just to make sure I understood what happened in this video.. So should I basically get some kind of splitter and insert it to the existing electrical outlet which is going to car's rear lights, and then get one more cable with electrical plug fitting the trailer input and insert it in the splitter? I hope I was clear enough.. Thanks again!
    – Eugene S
    Jun 24, 2013 at 4:49
  • 2
    It is effectively a splitter, yes. You would get this from your Toyota service station or dealer.
    – Rory Alsop
    Jun 24, 2013 at 8:30

The following applies to wiring basic rear lights for an un-braked trailer.

Wiring up tow-bar electrics is fairly simple if you have a few tools, even if the car doesn't have a connector specifically for a tow-bar connection. You need not know the colour scheme of the car's wiring either. Each pin on the tow-ball plug goes directly to the positive wire for the relevant light. There is also a ground connection.

You will need:

  • Standard toolkit with screwdrivers, sockets, pliers, and snips.
  • Spade connectors to make a firm connection between two wires

  • A test lamp (An electric test screwdriver with a spiked point, and the other end a crocodile clip to fasten to an earthing point)

Test Lamp

  • The tow-bar electrics kit (Basically the tow-ball plug which will have a 7 core cable on one end).

Tow-ball Plug

  • A friend to help you.

Larry has written a good answer about towbar electrics by the way: How should the lights for a trailer be hooked up?

The basic colour code for the cable coming from the plug is:

  • Yellow - Left Indicator
  • Green - Right Indicator
  • Black - Left Tail Light
  • Brown - Right Tail Light
  • Blue - Fog Lights
  • Red - Brake Lights
  • White - Ground Connection

    1. Start by fitting the plug beside the tow-ball. A good plug will include a metal plate which is mounted between the frame and the tow-ball. You should then run the cable into the back of the car. There should be a gromit on the back of the car which can be removed to run the cable through.

    2. Luckily my Honda CRV had a connector designed specifically for the tow-bar, so I was able to remove this and crimp the cores from the plug in directly. If your vehicle doesn't have this you must locate the wiring loom which leads to the rear lights. This may be behind the interior panelling, so remove this where applicable. Use common sense in terms of tracing forward from the lights to locate the loom. Once you have located the loom loosen it up by removing the sticky tape.

    3. Connect the negative end of the test lamp to a good earth (a metal point on the chassis for example). Note that in the vehicle the chassis is connected to the ground on the battery. There should also be a ground wire in the loom. This is ususally thicker, and coloured black or brown - make note of this as you will conenct it later.

    4. Ask your friend to put the left indicator on, then using the sharp, positive end of the test lamp spike the individual wires in the loom until the test lamp flashes in sequence with the turn signal. Have them switch the indicator off, and make sure the test lamp stops flashing. You have identified the left indicator. Connect the yellow core from the plug to this core with a scotch lock: place both cores in the scotch lock and close it with the pliers.

    5. Repeat the above step to locate the right indicator. For the brake lights have your friend depress the pedal, then once you have found the correct wire (test lamp is lit) they should tap the pedal to confirm, and do the same for the tail lights. Connect the relevant wires according to the above colour table.

    6. Finally connect the gound wire to the white core from the plug.

    7. Hook the trailer up, and have your friend activate all the lights while you observe the trailer to confirm everything works.

  • 4
    Please, don't use scotch locks - they are evil! Almost every dodgy wiring fault I've had to diagnose has come down to someone bodging something with scotch locks... Use proper Lucar spade connectors... Also, Steps 4 & 5 can be replaced by checking the workshop manual for the car which ought to have a wiring diagram - this will give colour codes for each wire.
    – Nick C
    Aug 12, 2013 at 13:22
  • 1
    What Nick C said, times 10! Scotch Locks are horrible. Previous owner did a bunch of rewiring of my car with them, and we've had to find and pull them all as they have been a never ending source of trouble. Besides complete failures I had a whole set of intermittent failures due to those awful connectors! Aug 12, 2013 at 16:22

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