# ISO standards for trailer connectors

A number of ISO standards cover trailer connectors, the electrical connectors between vehicles and the trailers they tow that provide a means of control for the trailers. These are listed below, with notes on significant deviations from them that can cause problems.

## Trailer connectors between the trailer and passenger car, light truck or heavy trucks with 12V systems

In Europe, both 7-pin (ISO 1724) and 13-pin (ISO 11446) are common. The 13-pin version being phased in is newer, provides more services than the 7-pin, a more positive locking and also better protection against moisture and contamination.
The connectors are designed for 12V systems. Exceptions for the 7-pin connector may exist where they may be used for 6V and 24V.
Vehicles and trailers with 6V systems can use the 7-pin or a 5-pin connector, but these are rare today. Heavy trucks that may have 12V systems are usually older (vintage vehicles) or on non-European markets.
The color coding is defined in ISO 4141-3, but the standard color codes are not always followed and may be different for a particular vehicle.

### 13-pin trailer connector (ISO 11446)

Physical design of the standard ISO 11446 but also called Jaeger-connector from the company that developed it.
| # | DIN | Signal | Color | Rec. cross-section | Rec. cross-section | Notes |
| # | DIN | Signal | Color | mm² | AWG | Notes |
| 1 | L | Left turn signal | Yellow | 1.5 | 15 | |
| 2 | | Rear fog lamps | Blue | 1.5 | 15 | |
| 3 | 31 | Ground (-) for pin 1 - 8 | White | 2.5 | 13 | |
| 4 | R | Right turn signal | Green | 1.5 | 15 | |
| 5 | 58R | Tail lamps, clearance lamps/outline marker lamps and registration plate lamp right side | Brown | 1.5 | 15 | |
| 6 | 54 | Stop lamps | Red | 1.5 | 15 | |
| 7 | 58L | Tail lamps, clearance lamps/outline marker lamps and registration plate lamp left side | Black | 1.5 | 15 | |
| 8 | | Reversing lamps, control current to block surge brakes when reversing. | Pink | 1.5 | 15 | |
| 9 | 30 | +12V permanent | Orange | 2.5 | 13 | |
| 10 | 15 | +12V via ignition lock | Grey | 2.5 | 13 | |
| 11 | 31 | Ground (-) for pin 10 | Black/White | 2.5 | 13 | |
| 12 | | Reserved for future allocation | Light Grey | 1.5 | 15 | |
| 13 | 31 | Ground (-) for pin 9 | Red/White | 2.5 | 13 | |
The following supplementary information exists for the connector:
* 1 2 3 Pin 3, 11 and 13 must not be joined in the trailer to avoid interaction between circuit types and over current if one ground pin isn't working.
* 1 2 Pin 5 and 7 must not be joined in the trailer to avoid problems in vehicles with separate circuits for left and right side.
* ↑ Previously allocated to trailer detection in ISO 11446:2002 (the vehicle could detect it was coupled to a trailer using a link between pin 12 and pin 3 in the trailer plug). This function was removed by ISO 11446:2004 and the pin reallocated to reserved. The pin remains reserved for future allocation in ISO 11446-1:2012.
Other variants of this connector exists but they are rare. One is used in 24V applications while the other is for ADR use. The difference is how they are mechanically keyed. These connectors are not very common.

### 7-pin trailer connector for ABS/EBS (ISO 7638-2)

Physical design according to standard ISO 7638-2.
This connector is intended to be used for 12V ABS and EBS on heavy duty trailers.
Identified by key tab on outer ring between pin 3 and 4.
| # | DIN | Signal | Color | Rec. cross-section | Rec. cross-section | Notes |
| # | DIN | Signal | Color | mm² | AWG | Notes |
| 1 | 30 | +12V permanent for control valves | Red | 4 | 11 | |
| 2 | 15 | +12V via ignition lock for electronics | Black | 1.5 | 15 | |
| 3 | 31 | Ground for electronics(Pin 2) | Yellow | 1.5 | 15 | |
| 4 | 31 | Ground for control valves (Pin 1) | Brown | 4 | 11 | |
| 5 | | ABS Fault indication (Active low, i.e. when the voltage is below +5V) | White | 1.5 | 15 | |
| 6 | | CAN H, For EBS and ABS | Green/White | 1.5 | 15 | [ISO7638-2 1] [ISO7638-2 2] |
| 7 | | CAN L, For EBS and ABS | Brown/White | 1.5 | 15 | [ISO7638-2 1] [ISO7638-2 2] |
The following supplementary information exists for the connector:
* 1 2 CAN bus communication according to ISO 11992.
* 1 2 The CAN bus is not necessary for the ABS to work which means that there are also a 5-pin variant of this connector where the CAN bus pins are excluded.

### 7-pin trailer connector Type 12N (ISO 1724)

Physical design according to standard ISO 1724.
The 7-pin connector uses all 7 pins on newer trailers according to the ISO standard.
On older trailers there's sometimes a 5-wire setup using a 7-pin connector. In these cases exclude connection for right tail light (58R) and rear fog light (54G) and connect the tail lights only to pin for left tail light (58L).
Joining the pins for right and left tail lights (58R and 58L) can cause problems on German cars where it is possible to activate Standing Lamps on only one side of the vehicle.
| # | DIN | Signal | Color | Rec. cross-section | Rec. cross-section | Notes |
| # | DIN | Signal | Color | mm² | AWG | Notes |
| 1 | L | Left turn signal | Yellow | 1.5 | 15 | |
| 2 | 54G | +12V from battery or Rear fog lights | Blue | 1.5 | 15 | |
| 3 | 31 | Ground connected to chassis | White or Grey | 2.5 | 13 | |
| 4 | R | Right turn signal | Green | 1.5 | 15 | |
| 5 | 58R | Tail lights, clearance lights/outline marker lights and registration plate light right side | Brown | 1.5 | 15 | |
| 6 | 54 | Stop lights | Red | 1.5 | 15 | |
| 7 | 58L | Tail lights, clearance lights/outline marker lights and registration plate light left side | Black | 1.5 | 15 | |

#### Pin 2 (54G)

According to DIN 72552 pin 54G was initially intended for electrical control of brakes on trailers.
Later pin 2 (54G) has been used for a variety of functions different from the original intent. A few examples:
* +12V permanent.
* +12V via ignition lock.
* Rear fog lights.
* Reversing lights.
This is why in regions using this connector, trailers on the road are occasionally seen with the rear fog lights on when they should be off. (Vehicle wired for +12V, permanent or via ignition and trailer wired for fog lamps)

#### Special case for Australia

Australia uses basically the same wiring with the exception for pin 5 and pin 2. The problematic part here is that pin 5 is used for trailer brake which means that if you for some reason connect an Australian trailer to a towing vehicle with ISO wiring you will get into trouble with the trailer brakes being applied as soon as you turn on the lights.
Further reading at Trailer Connector/Australia.

### 7-pin trailer connector Type 12S (ISO 3732)

Physical design according to standard ISO 3732.
Signals in this connector (if following the standard) are not generally legally required (local regulations may still apply), which means that it is not mandatory to connect it if it is present.
This connector is basically the same as the 12N (ISO 1724) connector, but the center pin (pin 7) has changed gender to make the plug and outlet unique. Socket is replaced with pin in the plug, pin is replaced with socket in outlet.
The purpose of this connector is to supplement the 12N (ISO 1724) connector for power supply of consumers common in caravans (Travel trailers). This is used in Great Britain but may also be used in other areas of Europe.
There are two main variants of the wiring with a switchover date 1999. The difference is that an additional connection for ground and that battery charging in the trailer is shared with other consumers. This means that if a pre-1999 camper trailer with a battery is connected to a post 1999 vehicle there's a risk that the battery charging won't work.
The combination of 12N+12S was replaced in 2008 by the 13-pin ISO 11446 connector.
| # | DIN | British | ISO 3732 | Color | Rec. cross-section | Rec. cross-section | Notes |
| # | DIN | -1999 | 1999-2008 | Color | mm² | AWG | Notes |
| 1 | | Reversing lamps | Reversing lamps | Yellow | 1.5 | 15 | |
| 2 | (15) | Battery charging | Spare | Blue | 2.5 | 13 | |
| 3 | 31 | Common ground | Common ground except for pin 6 | White or Grey | 2.5 | 13 | |
| 4 | 30 | Feed for internal 12V equipment except refrigerator | +12V permanent | Green | 2.5 | 13 | |
| 5 | | Spare | Spare | Brown | 1.5 | 15 | |
| 6 | 15 | Feed for refrigerator | +12V via ignition lock | Red | 2.5 | 13 | |
| 7 | | Spare | ground for pin 6 | Black | 2.5 | 13 | |
The following supplementary information exists for the connector:
* ↑ Attention shall be paid to the fact that this pin may not be powered if the towing vehicle is manufactured after 1999 and if the trailer has a battery that is charged by the towing vehicle. The result may be that the battery wouldn't be charged as expected.

### 5-pin connector (ISO 1724)

Physical design according to standard ISO 1724.
The 5-pin has a design and pin layout that is identical to the 7-pin ISO 1724 connector with the exception for the lack of pin 1 (L) and pin 4 (R). This connector is sometimes present on vintage vehicles and the actual wiring may be completely different from what the standard states which means that measuring before connecting is a good idea.
Whenever there is a need to change the plug or outlet it can be replaced with a 7-pin.

## Trailer connectors between heavy duty trailer and the tractor unit

These connectors are designated as 24 volt.

### 15-pin trailer connector (ISO 12098)

Physical design according to standard ISO 12098.
This connector is present on newer heavy duty commercial trucks and trailers following the ISO standard and is intended to replace the combination of connectors according to standards ISO 1185 and ISO 3731. The 15-pin connector is not designed to replace the ISO 7638 connector.
| # | DIN | Signal | Color | Rec. cross-section | Rec. cross-section | Notes |
| # | DIN | Signal | Color | mm² | AWG | Notes |
| 1 | L | Left turn signal | Yellow | 1.5 | 15 | |
| 2 | R | Right turn signal | Green | 1.5 | 15 | |
| 3 | | Rear fog lamps | Blue | 1.5 | 15 | |
| 4 | 31 | Ground (-) for pin 1 - 3 and 5 - 12 | White | 2.5 | 13 | |
| 5 | 58L | Tail lamps, clearance lamps/outline marker lamps, identification lamps and registration plate lamp left side | Black | 1.5 | 15 | [ISO12098 1] [ISO12098 2] |
| 6 | 58R | Tail lamps, clearance lamps/outline marker lamps, identification lamps and registration plate lamp right side | Brown | 1.5 | 15 | [ISO12098 1] [ISO12098 2] |
| 7 | 54 | Stop lamps | Red | 1.5 | 15 | |
| 8 | | Reversing lamps | Pink | 1.5 | 15 | |
| 9 | 30 | +24V permanent | Orange | 2.5 | 13 | |
| 10 | | Brake wear indicator | Grey | 1.5 | 15 | |
| 11 | | Indication of applied parking brake due to loss of air pressure | Black/White | 1.5 | 15 | |
| 12 | | Lift Axle | Blue/White | 1.5 | 15 | |
| 13 | 31 | ground (-) for pin 14 and 15 | Red/White | 2.5 | 13 | |
| 14 | | CAN H, Not for EBS or ABS | Green/White | 1.5 | 15 | |
| 15 | | CAN L, Not for EBS or ABS | Brown/White | 1.5 | 15 | |
The following supplementary information exists for the connector:
* 1 2 Pin 5 and 6 must not be joined in the trailer to avoid problems in vehicles with separate circuits for left and right side.
* 1 2 Identification lamps shall be wired to either pin 5 or 6, not both.
* 1 2 EBS and ABS shall be connected through the ISO 7638 connector.
Notice: There was a predecessor to this connector with 13 pins that on a cursory glance is identical to the 15 pin connector but has a different arrangement of the pins. It was not very common but may exist on some vehicles and can result in an unpleasant surprise.

### 7-pin trailer connector for ABS/EBS (ISO 7638-1)

Physical design according to standard ISO 7638-1.
This connector is intended for 24V ABS and EBS on heavy duty trailers.
Identified by key tab on outer ring by pin 5.
| # | DIN | Signal | Color | Rec. cross-section | Rec. cross-section | Notes |
| # | DIN | Signal | Color | mm² | AWG | Notes |
| 1 | 30 | +24V permanent for control valves | Red | 4 | 11 | |
| 2 | 15 | +24V via ignition lock for electronics | Black | 1.5 | 15 | |
| 3 | 31 | Ground for electronics(Pin 2) | Yellow | 1.5 | 15 | |
| 4 | 31 | Ground for control valves (Pin 1) | Brown | 4 | 11 | |
| 5 | | ABS Fault indication | White | 1.5 | 15 | |
| 6 | | CAN H, For EBS and ABS | Green/White | 1.5 | 15 | [ISO7638-1 2] [ISO7638-1 3] |
| 7 | | CAN L, For EBS and ABS | Brown/White | 1.5 | 15 | [ISO7638-1 2] [ISO7638-1 3] |
The following supplementary information exists for the connector:
* 1 2 Active low, i.e. when the voltage is below +5V.
* 1 2 CAN bus communication according to ISO 11992.
* 1 2 The CAN bus is not necessary for the ABS to work which means that there are also a 5-pin variant of this connector where the CAN bus pins are excluded.

### 7-pin trailer connector 24N (ISO 1185)

Physical design according to standard ISO 1185.
This connector is common on heavy duty commercial trucks and trailers but is replaced by the ISO 12098 connector on newer vehicles.
| # | DIN | Signal | Color | Rec. cross-section | Rec. cross-section | Notes |
| # | DIN | Signal | Color | mm² | AWG | Notes |
| 1 | 31 | Ground (-) | White | 2.5 | 13 | |
| 2 | 58L | Tail lamps, clearance lamps/outline marker lamps, identification lamps and registration plate lamp left side | Black | 1.5 | 15 | [ISO1185 1] [ISO1185 2] |
| 3 | L | Left turn signal | Yellow | 1.5 | 15 | |
| 4 | 54 | Stop lamps | Red | 1.5 | 15 | |
| 5 | R | Right turn signal | Green | 1.5 | 15 | |
| 6 | 58R | Tail lamps, clearance lamps/outline marker lamps, identification lamps and registration plate lamp right side | Brown | 1.5 | 15 | [ISO1185 1] [ISO1185 2] |
| 7 | | Trailer brake control according to ISO 1185, SAE J560 use is different | Blue | 1.5 | 15 | |
The following supplementary information exists for the connector:
* 1 2 Pin 2 and 6 must not be joined in the trailer to avoid problems in vehicles with separate circuits for left and right side.
* 1 2 Identification lamps shall be wired to either pin 2 or 6, not both.
The physical design is also used by SAE J560 with basically the same configuration. The difference is that SAE J560 uses 12V (larger wire cross-section and higher amp rating on fuses). Pin 7 may also have a different behavior on SAE J560.

### 7-pin trailer connector 24S (ISO 3731)

Physical design according to standard ISO 3731.
This connector is common but on newer vehicles it is replaced by the connectors according to ISO 12098 and ISO 7638.
| # | DIN | Signal | Color | Rec. cross-section | Rec. cross-section | Notes |
| # | DIN | Signal | Color | mm² | AWG | Notes |
| 1 | 31 | Ground (-) | White | 2.5 | 13 | |
| 2 | | ABS Fault indication | Black | 1.5 | 15 | |
| 3 | | Reversing lamps | Yellow | 1.5 | 15 | |
| 4 | 30 | +24V permanent | Red | 2.5 | 13 | |
| 5 | | Control via Ground | Green | 1.5 | 15 | |
| 6 | 15 | +24V via ignition lock | Brown | 2.5 | 13 | |
| 7 | | Rear fog lamps | Blue | 1.5 | 15 | |