connector or cable wiring scheme
16 pin car OBD2 special connector at the car
This page documents a universal OBD-II adapter that supports all three legacy diagnostic protocols — SAE J1850 PWM (used in pre-2008 Ford vehicles), SAE J1850 VPW (used in pre-2008 GM vehicles), and ISO 9141-2 (used in Chrysler, European, and Asian vehicles) — through the standard 16-pin Data Link Connector (DLC) defined by SAE J1962 and its ISO equivalent ISO 15031-3. The OBD-II system became mandatory in the United States for petrol passenger cars from model year 1996 and for light trucks from the same year. The adapter passes through the relevant protocol pins — pin 2 (J1850 bus+), pin 7 (K-line), pin 10 (J1850 PWM bus−), and pin 15 (L-line) — alongside the mandatory ground and power pins (4, 5, and 16), allowing a single interface circuit to communicate with vehicles using any of these three bus implementations.
| Pin | Signal | Description |
|---|---|---|
| 2 | J1850 Bus+ | SAE J1850 PWM bus+ / J1850 VPW single-wire bus |
| 4 | Chassis Ground | Vehicle chassis earth |
| 5 | Signal Ground | Signal return |
| 7 | K-line | ISO 9141-2 / ISO 14230-4 K-line (bidirectional) |
| 10 | J1850 Bus− | SAE J1850 PWM bus− (PWM only) |
| 15 | L-line | ISO 9141-2 / ISO 14230-4 L-line (wake-up, optional) |
| 16 | Battery Power | Battery positive, +12 V (Type A connector) |
Notes
- Do not connect external power sources — all power is derived from pin 16 of the OBD-II DLC (battery positive, 12 V on Type A connectors).
- The serial port operates at 19,200 baud.
- J1850 PWM uses two-wire differential signalling: pin 2 (bus+, active 5 V) and pin 10 (bus−, active 0 V) at 41.6 kbps; used in pre-2008 Ford vehicles.
- J1850 VPW uses a single wire on pin 2 (7–8 V active) at 10.4 kbps with variable-pulse-width encoding; used in pre-2008 GM vehicles.
- ISO 9141-2 uses pin 7 (K-line, idle high at 12 V via 510-ohm pull-up) and optionally pin 15 (L-line, unidirectional wake-up only) at 10.4 kbaud, 8N1, half-duplex; used in Chrysler, European, and Asian vehicles.
- The maximum OBD-II adapter cable length is 5 m per SAE J1962.
References
- SAE J1962: Diagnostic Connector — SAE International
- How OBD-II Vehicle Diagnostics Work, Part 2 — Circuit Crush
- Automotive Diagnostic Standards — x-engineer.org