The ISO 7638 is a 7 pin electrical trailer coupling that provides both power to the main trailer ECU (the trailer 'brain') and allows the tractor unit and trailer to transfer CAN data.
It is common throughout Europe and is often known as an 'EBS', 'ABS' or 'ISO' coupling.
Why is this so important?
The ISO 7638 connection is not well understood by many drivers but is a critical connection for many reasons. It's also became a legal requirement in May 2002
Most will recognise the familiar ABS acronym relating to anti-lock braking but what they don’t necessarily realise is what else it does. The ISO 7638 provides fast, electrical braking response time where, by default, it must rely on the slower, pneumatic signal speed. The ECU also calculates information about trailer weight (load sensing) so that braking is proportionate and doesn’t result in trailer brakes locking up when carrying a light load. In addition, the ECU controls the trailer roll stability system (RSS) to prevent roll-overs at roundabouts or bends. The last main function of the ABS/EBS line and ECU is to ensure the trailer suspension operates correctly at ride height; irrespective of payload weight. Suspension height becomes extremely important when you’re driving a 16’3” high double deck under 16’6” clearance bridges.
Fun fact: Did you know that the term “Susie” relating to coupling coils is a trade mark owned by Unipart and originates back to the old Slinky toy, “Susie, the Lovable Slinky Worm”?
Published: Fri 17 Nov 2023
Updated: Fri 19 Jan 2024