ISO 11446 – 13 Pin Trailer Connections


ISO 11446 details the connections and standards used in the 13 Pin Trailer connector. The connector was developed in the late 80’s by Erich Jaeger as the demands of the automotive industry required additional electrical circuits to be connected to trailers. They are sometimes known as “Jaeger” connectors – especially in Europe.

ISO 11446 is broken into two parts:

    • ISO 11446-1 13-pole connectors for vehicles with 12 V nominal supply voltage not intended to cross water fords.
    • ISO 11446-2 13-pole connectors for vehicles with 12 V nominal supply voltage intended to cross water fords.

The standard title always identifies the year and revision in its title:

ISO 11446-1:2012-05

The above is decoded as Standard 11446 Part 1 dated 2012 revision 05. If it is ‘draft’ or ‘proposed’ it will always state this after the revision number.

The current standard specifies the following pin allocations (the table is exactly as per the standards document):

ISO 11446-1-2012 Connections

(You can click on the above table to open it full size)

When ever you are having a tow bar fitted with towing electrics it is important that you always choose either ‘OEM’ (electrical kit produced by/for the vehicle manufacturer for your specific vehicle) or “vehicle specific” (electrical kit produced by an independent supplier specifically for your make and model of vehicle) and check it is fully ISO 11446-1:2012 compliant. It is not recommended to install a “generic” electrical towing kit that is simply wired into the vehicles electrical system. Although it will seem cheaper at the time, in the long run it could cost you a lot more in revisiting the installer and fault-finding. In fact most manufacturers now state that installing a non manufacturer approved electrical towing kit will invalidate any vehicle warranty and could compromise any on-board vehicle electrical safety systems.

Unfortunately some vehicle manufacturers (OEM) and vehicle specific electrical towing kits are not fully compliant and do not include connections for the fridge (Pin10) of charging the leisure battery (Pin 9). Notably BMW, Audi and Volkswagen seem to produce kits that are not fully compliant.

Additionally if you have an independent auto electrician install a towing electrics kit, you must ensure that it is fully compliant with the ISO standard AND the vehicle manufacturers specifications – which could include a software update to the vehicles ECU so that the vehicle on board systems (ESP, ABS & Trailer Control) are activated and functioning correctly.

Important

Some vehicles use the trailer grounding Pin 12 to signal to the vehicles ECU that a trailer is connected. The ECU uses this information in various ways – to change the ABS settings, alter the ESP programme and mute the reverse sensors (if fitted) along with on some vehicles turn off the rear fog lights on the vehicle. It is important then that you do not make any modifications to the trailers electrical system that affects the ground connection between Pin 12 and Pin 3 on your trailer. (NOTE: some pre 2012 caravans/trailers that use the 13 pin plug will not have implemented this, if you have just changed to a new tow vehicle, it is worth checking if your vehicle needs this and that the caravan/trailer is suitably wired).

Some vehicles do not use pin 12 to detect if a trailer is connected, they detect the presence of a trailer by sending signals via the CANBUS system to detect if trailer lights are present on the 13 pin towing socket. Its worth finding out how your vehicle detects the presence of a trailer.

How much….!

Because of Copyright rules on the official standards document, I cannot reproduce it here in full and if you want a copy you have to pay nearly £100 for all 14 pages of it. I can understand making some charge – say around £5 to £10 for an electronic version, the current charges though are just silly. However I hope the above gives you enough information.

Copyright © 2011 – 2016 Simon P Barlow – All rights reserved

10 thoughts on “ISO 11446 – 13 Pin Trailer Connections”

  1. Very enlightening article put in plain English…. But…. Is my fridge working when the engine is running I’m unsure because the light doesn’t come on in the fridge!? It comes on when the engine is off, does the habitation rely also control the fridge light? My set up is a sterling Europa, N90 fridge wired through 12n/s sockets on a 2005 Honda crv. Also the charging meter is fully into the green when the engine is running

    • Hi Rob
      There are two separate 12 volt supplies to your fridge.

      The first provides power to operate the gas valve, power the interior light and power the LCD display on fridges fitted with these and is provided by the leisure battery.

      The second 12 volt supply is provided by the towing vehicle when the engine is running and only powers the 12 volt heating element.

      On the N90 fridge without the LCD display the only way to be absolutely sure that the fridge is running OK when the vehicle engine is running is to check the voltage across the terminals for the 12 volt heating element with the engine running. If 12 volts (usually it will be slightly more than 12) is measured then everything should be OK assuming the heating element is OK. If 12 volts is measured and you suspect the fridge isn;t working, then checking the resistance of the heating element with the power off and the element disconnected for testing will confirm if the element is OK or not. The resistance reading for the DC heater element should be between 0.93 Ohms and 1.13 Ohms.

      If it has the LCD display the following error codes apply:

      Error Code 1 – AC Heater current is 75% below nominal current
      Error Code 2 – DC Heater current is 75% below nominal current
      Error Code 3 – AC Heater is ON when it should be OFF
      Error Code 4 – DC Heater is ON when it should be OFF
      Error Code 5 – Senses flame when gas should be OFF
      Error Code 6 – Senses gas output terminal ON when should be OFF
      Error Code 7 – Senses gas output terminal OFF when should be ON
      Error Code 8 – AC Mains supply is below 20% nominal
      Error Code 9 – Gas lockout because flame fails to ignite after 30 seconds
      Error Code 10 – No engine running signal is present and control is in Manual DC mode
      Error Code 11 – No energy source available and control is on AUTO mode
      Error Code 12 – Supply voltage DC is out of range (9.5v – 15.5v)
      Error Code 13 – Thermistor fails, control automatically switches to backup mode (BOS)
      Error Code 14 – Display board and power board lost communication to each other

      S

  2. Hi, very good site and I’ve gained a lot of insight from plain English instructions. However I still cant find why my Reverse light on my caravan is permanently on when my 13 pin is connected from the car? Any ideas
    Thanks
    Steve

    • Hi Steve
      The reversing light is connected to pin 8 on the 13 pin plug and right next to it pin 9 is the permanent feed for the leisure battery circuit. So my first guess is there is a stray strand of wire bridging these two.

      I’d check the towing socket on the vehicle, put a voltmeter positive on pin 8 (reversing light) and the negative lead on pin 3 (earth for road lights).. if it reads 12 volts or more, the problem is in the towing socket.

      To check the caravan plug, switch a multimeter over to Ohm range and take a reading between pins 8 and 9. If it shows less than 1 ohm, the problem is in the plug… or where the multicore cable terminates in the caravan.

      The pin outs for the towing socket as seen from the plug side are here: https://caravanchronicles.com/guides/13-pin-socket-basic-fault-finding/

      S

  3. can someone help ive changed my electrics to a 13 pin and all lights work except the ones on the top sides of the caravan not sure what these are called.

    • Hi Pete
      I assume you mean the red/white lights on the side of the caravan at the rear… these are known as marker lights or clearance lights. They are usually connected to the same supply as the rear side lights and the front white marker lights.

      Pin 5 for the left side/marker lights and pin 7 for the right side/marker lights.

      If all the other lights work as correctly expected and the top lights on both sides don’t I would look to see if there is a common earth for these two lights that has become detached as it would be unusual for both to fail because of a connection problem on the supply side. The earth should be connected to pin 3.

      S

  4. Thanks for the reply I’ve tried what you said but still no joy

    • Hi Pete

      The next step would be to remove one of the marker light cover and using a multimeter check the bulb, then check to see if you had a +ve supply to the fitting and an earth return path.

      Seems unusual both have gone off at the same time, that would make me think loss of earth or loss of +ve for both fittings.

  5. Contact 12 was “Coding for coupled trailer” only in the long withdrawn ISO 11446:2002, which specified this contact should be tied to contact 3 in the (trailer) plug for detection purposes. Contact 12 is “Reserved for future allocation” in ISO 11446:2004 and ISO 11446-1:2012.

    So far as I am aware, few if any vehicles attempted to use contact 12 to detect a trailer is connected and no new vehicle should be attempting to do so considering how many years have passed since ISO 11446:2002 was withdrawn. Vehicles that try to detect a connected trailer use a microswitch in the 13 pin socket housing that is operated by inserting a plug and/or when bulb failure detection pulses on the lighting lines show trailer lighting is connected.

    The standard core insulation colours are found in ISO 4141-3 (the latest version at this time is ISO 4141-3:2006).

    It is debatable whether specifying vehicle electrics are “fully ISO 11446-1:2012 compliant” is sufficient to ensure all 12 contacts with an allocated function are connected. The standard gives the “contact allocation” (see section 1 of the standard if you have sight of a copy) but does not appear to specify that every contact must be wired as allocated in a vehicle socket. To my reading of the standards, a vehicle installation that omits one or more of contacts 9, 10, 11 and 13 is still ISO 11446-1:2012 compliant, including the requirements of ISO 4091 incorporated by reference via section 6 of ISO 11446-1:2012. An installation is definitely not ISO 11446-1:2012 compliant if any of the contacts are connected in a way that conflicts with the standard, such as pin 10 incorrectly being permanent +12V.

    I suggest anyone who wants vehicle electrics to include switched and permanent power circuits in addition to the lighting circuits specifies “all 13 contacts (other than contact 12) in the vehicle socket to be connected in accordance with ISO 11446-1:2012”, which is unambiguous.

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