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7-Way Trailer Wiring Chart

Pin numbers, wire colors and circuit functions for the SAE J560 seven-conductor connector used between heavy-duty tractors and trailers.

Ref FA-0070SAE J560

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

SAE J560 defines the seven-conductor round-pin connector and cable used to carry lighting and auxiliary power from a heavy-duty tractor to a trailer. It is the standard "7-way" on Class 7 and 8 equipment. The center pin (pin 7) carries constant power, which on trailers built since the federal trailer ABS rule is used to power the trailer ABS.

This is not the flat-blade RV-style 7-way connector used on pickups and light trailers. That connector has a different pin layout and wiring.

How to identify

Look at the face of the socket on the tractor or the nose box on the trailer. The pins are numbered around a center pin. The larger pin is usually the ground (pin 1, white), and the socket has a keyway so the plug fits only one way. Pin numbers are often molded into the plug or socket.

Pin chart

Pin	Wire color	Circuit
1	White	Ground return
2	Black	Clearance, side marker and identification lamps
3	Yellow	Left turn signal and hazard
4	Red	Stop lamps
5	Green	Right turn signal and hazard
6	Brown	Tail, clearance and license plate lamps
7	Blue	Auxiliary; constant power for trailer ABS

Key points

Ground (pin 1) and ABS power (pin 7) carry the most current and often use heavier conductors. Use cable built to SAE J2394 or the trailer maker's spec.
Pin 2 and pin 6 functions are sometimes split differently by fleets. Check the trailer's wiring diagram before rewiring.
Corrosion at the nose box and plug causes most trailer light faults. Inspect pins, use dielectric grease as the connector maker allows, and keep the dust cover closed.
A green "ABS" lamp on the trailer or a tractor dash warning can point to low or missing voltage on pin 7.

Common mistakes

Wiring a heavy-duty trailer with an RV-style 7-way pinout.
Using a chassis bolt for ground instead of the white pin 1 return, which causes dim or flickering lamps.
Replacing the 7-way cord with a light-duty cable that is not rated for the current or the flexing.
Leaving pin 7 unpowered, which disables trailer ABS.

Governing standards: SAE J560 (primary and auxiliary seven-conductor electrical connector for truck-trailer jumper cable); SAE J2394 (seven-conductor cable for ABS power). 49 CFR 393.55 for trailer ABS requirements.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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