SAE J1708 / J1587
J1708
J1708 is the legacy serial bus used on heavy-duty trucks built before roughly 2007, with J1587 as the application-layer protocol carrying engine, transmission, and brake messages.
SAE J1708 is the older serial bus used on heavy-duty trucks built before approximately 2007, before J1939 (CAN-based) became the industry default. Physically, J1708 is a half-duplex two-wire bus running at 9.6 kbit/s; logically, the application layer is defined by SAE J1587, which assigns Message Identifiers (MIDs) to each ECU and parameter IDs (PIDs) to each signal.
While J1939 has long since replaced J1708 on new vehicles, a large fleet of older Cummins, Detroit, CAT, and International trucks still in revenue service exposes only J1708 at the dash. Diagnostic tools and pass-through adapters that target heavy-duty work generally support both protocols on the same physical 6- or 9-pin Deutsch connector — selectable per session.
ecuLink's gateway speaks J1708 in addition to J1939, so you can run legacy diagnostics on pre-2007 vehicles using the same hardware that handles modern J1939 trucks. The signaling rate is much lower than J1939, which can make remote sessions a little slower, but every J1708 service that works locally also works through the pass-through.
Related terms
J1939
SAE J1939
SAE J1939 is the standard CAN-based communication protocol used by heavy-duty trucks, buses, and off-highway equipment to share engine, transmission, brake, and emissions data on a single wiring bus.
RP1210
TMC RP1210
RP1210 is the Technology & Maintenance Council's Windows API for heavy-duty diagnostic adapters. It lets one diagnostic application talk to many vendors' VCIs through a common interface.
CAN Bus
Controller Area Network
CAN bus (Controller Area Network) is the differential, multi-master serial bus used by virtually every modern vehicle to let ECUs share short messages without a central host.
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