ISO 11446

ISO 11446
Type	Trailer Connector
Superseded	ISO 1724 (12N); ISO 3732 (12S)
General specifications
Pins	13
Pinout
Pin 1	Left indicator
Pin 2	Rear fog lamp
Pin 3	Ground
Pin 4	Right indicator
Pin 5	Right tail lamp
Pin 6	Brake lamp
Pin 7	Left tail lamp
Pin 8	Reverse lamp
Pin 9	Permanent power
Pin 10	Switched supply (for fridge)
Pin 11	Ground for pin 10
Pin 12	Trailer Presence Detection
Pin 13	Ground for pin 9

ISO 11446:2004 specifies a 13-pole electrical connector between towing and towed vehicles with 12 volt electrical system. It was developed in 1987 by Erich Jaeger to replace older 7-pin plugs.

Notes

1 2 3 Pins 3, 11 & 13 must not be joined in the trailer to prevent ground loops
1 2 Pins 5 & 7 must not be joined in the trailer without a pair of diodes
↑ Pin 12 was assigned prior to 2012; older vehicles could be using this for a different function

References

↑ "ISO 11446 - the JAEGER system for trailer connectors".

Sources

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[fn1-1] 1 2 3 Pins 3, 11 & 13 must not be joined in the trailer to prevent ground loops

[fn2-2] 1 2 Pins 5 & 7 must not be joined in the trailer without a pair of diodes

[3] Pin 12 was assigned prior to 2012; older vehicles could be using this for a different function

[4] "ISO 11446 - the JAEGER system for trailer connectors".