SAE J560 7-Way Trailer Connector Pin-Out Reference
Which contact and colour carries which circuit in an SAE J560 7-way trailer connector, why white and blue are the heavy conductors, and how to trace a dead trailer circuit back to a terminal.
The SAE J560 7-way connector is the electrical interface that powers a trailer's lamps and its antilock braking system from the towing vehicle. Each of its seven contacts has a defined circuit and a defined wire colour. On the heavy-duty connector the large centre contact is contact 7, the blue conductor carrying continuous ABS primary power — not the ground. The white ground is contact 1, one of the outer contacts. Those two are the ones most often transposed in workshop notes, and getting them the right way round is where a trailer wiring diagnosis starts.
The primary J560 pin-out
| Contact | Wire colour | Circuit |
|---|---|---|
| 1 | White | Ground return to the towing vehicle |
| 2 | Black | Clearance, side-marker and identification lamps |
| 3 | Yellow | Left turn and hazard signal |
| 4 | Red | Stop lamps; ABS secondary power |
| 5 | Green | Right turn and hazard signal |
| 6 | Brown | Tail and licence-plate lamps, and applicable rear clearance and side-marker lamps |
| 7 | Blue | Continuous ABS primary power / auxiliary circuit |
This is the allocation for the primary SAE J560 heavy-duty trailer connector. It does not transfer to an RV-style blade connector, an ISO 1185 or ISO 7638 connector, or a J560 AUX connector — different allocations on different hardware, and a common source of miswiring.
Read the contact numbers, not the apparent layout
Contact numbers on the primary connector are defined, not a matter of manufacturer preference. What changes between diagrams is the view: a connector drawn looking at its mating face is a mirror image of the same connector drawn from the wiring side, so the arrangement can appear reversed. Work from the contact numbers marked on the connector body, and from a diagram whose view is explicitly labelled.
Colour is a cross-check, not proof: on a repaired, spliced or rebuilt harness a colour may no longer sit on its original contact. Confirm with a meter before cutting anything.
Why white and blue are the heavy conductors
Conductor sizes come from the cable standard, SAE J2394, not the connector standard: J560 governs the connector interface, J2394 the seven-conductor trailer jumper cable.
The construction published for heavy-duty ABS trailer cable is one 8 AWG white conductor, two 10 AWG conductors — red and blue — and four 12 AWG conductors in black, yellow, green and brown. The trade shorthand is 1/8-2/10-4/12.
White is the heaviest because it is the single return path for every other circuit. When stop lamps, both marker circuits and the tail lamps draw at once, all of it comes back through that one conductor. Corrode it, or break a few strands inside the coil, and the symptom is not a clean failure but dim, flickering lamps across the whole trailer that change brightness as other circuits switch.
Red and blue are both 10 AWG because both carry braking-system power: blue the continuous ABS primary supply, red the ABS secondary supply alongside the stop lamps. An ABS modulator actuating its valves draws far more current than any lamp circuit.
Treat 1/8-2/10-4/12 as the construction published for this class of ABS trailer cable, not as a universal minimum for anything with seven conductors. Older non-ABS constructions remain in circulation with a lighter blue conductor that was never intended to supply ABS primary power. Confirm the construction on the datasheet rather than counting conductors.
Diagnosing by circuit
Because each colour maps to one function, the failure pattern usually names the conductor for you.
| Symptom | Circuit to check first | Typical cause |
|---|---|---|
| Every trailer lamp dim or dead | White (ground) | Corroded ground terminal, broken ground conductor inside the coil |
| ABS warning lamp stays on | Blue (primary ABS power) | Voltage drop under load, damaged conductor, water in the socket |
| One side's turn signal dead | Yellow or green | Pushed-back terminal, conductor chafed at the coil end |
| Stop lamps dead, turn signals normal | Red | Open at the plug, or the feed from the towing vehicle |
| Marker and clearance lamps dead | Black | Open at the plug or socket |
| Tail lamps dead, stop lamps normal | Brown | Open at the plug or socket |
Measure at the trailer end with the circuit loaded, not at rest. Opens are easy to find; the faults that strand a combination are high-resistance joints that read near full voltage unloaded and collapse once current flows.
Where J560 trailer cable assemblies actually fail
Almost all of these faults are mechanical. Conductors in the middle of a cable rarely fail — the ends do. Flexing at the plug strain relief works strands until the bundle necks down, salt water tracks into the socket and corrodes terminals, and terminals spread by repeated coupling stop making firm contact. That is why replacing an assembly usually beats repairing one conductor in a bundle that has aged throughout.
Two construction choices extend end life: metal plug bodies resist crush damage better than moulded plastic, and coiled assemblies keep slack off the deck plate where straight cable drags in standing water.
Sourcing J560 trailer cable assemblies
Sertplas North America publishes 7-way ABS trailer connector cable assemblies with metal plugs in coiled and straight configurations, in 12 ft and 15 ft, plus a 7-pin metallic plug with a cable guard for rebuilding an existing assembly. The cable assemblies — not the bare plug — carry SAE J560 and SAE J2394 in their published compliance data: J560 for the connector interface, J2394 for the cable. Parts are manufactured in Turkey under IATF 16949 certified manufacturing and stocked in Farmington, Michigan, in the metro Detroit area.
Check current availability and the OEM cross-references on the product page: length, construction and plug material all vary within the same nominal 7-way description.