16 pin car OBD2 special connector at the car side
The Volkswagen Group (VAG) — covering VW, Audi, Seat, and Skoda — used a proprietary 2×2-pin diagnostic connector on vehicles produced before the group’s adoption of the standardised OBD-II 16-pin Data Link Connector. The connector routes K-line and L-line signals as defined by ISO 9141-2 and ISO 14230-4 (KWP2000), which are the same underlying protocols used on later OBD-II equipped VAG vehicles. No public OEM specification for the 2×2 housing itself has been published by Volkswagen AG. From 1996 onward, VAG vehicles fitted with OBD-II carry the standard SAE J1962 / ISO 15031-3 16-pin DLC in the passenger compartment alongside or in place of the proprietary plug.
| Pin | Signal | Description |
|---|---|---|
| 2 | J1850 Bus+ | |
| 4 | CGND | GND |
| 5 | SGND | GND |
| 6 | CAN High | J-2284 |
| 7 | ISO 9141-2 K-LINE | Tx/Rx |
| 10 | J1850 Bus- | |
| 14 | CAN Low | J-2284 |
| 15 | ISO 9141-2 L-LINE | Tx/Rx |
| 16 | +12v | Battery power |
Signals
- J1850 Bus+ — SAE J1850 bus positive; used for PWM (differential, pin 2 + pin 10) or VPW (single-wire, pin 2 only) diagnostic protocols.
- CGND — Chassis ground; mandatory on all OBD-II DLC variants per SAE J1962.
- SGND — Signal ground reference; mandatory on all OBD-II DLC variants per SAE J1962.
- CAN High — ISO 15765-4 CAN bus high line (pin 6); idles at approximately 2.5 V, rises to 3.5 V dominant.
- ISO 9141-2 K-LINE — Bidirectional K-line for ISO 9141-2 and ISO 14230-4 (KWP2000) communication; idles high at battery voltage, pulled low to transmit at 10.4 kbaud.
- J1850 Bus- — SAE J1850 PWM bus negative (differential pair with pin 2); not present in VPW single-wire configurations.
- CAN Low — ISO 15765-4 CAN bus low line (pin 14); idles at approximately 2.5 V, drops to 1.5 V dominant.
- ISO 9141-2 L-LINE — Unidirectional L-line; used only during the wake-up/initialisation phase of ISO 9141-2 and optionally ISO 14230-4; function on pre-OBD-II VAG variants is not publicly documented.
- +12v — Battery positive supply to the diagnostic tool; mandatory on all OBD-II DLC variants per SAE J1962.
Notes
The VAG proprietary 2×2 connector predates OBD-II and carries K-line (ISO 9141-2) and L-line signals to a vehicle-side adapter that connects to the standard 16-pin OBD-II DLC on VAG vehicles from 1996 onward. The 16-pin connector shown in the image above is the standard SAE J1962 / ISO 15031-3 Type A connector (12 V systems); it is a trapezoidal female socket located on the driver’s side of the passenger compartment. Mandatory pins across all OBD-II protocol variants are pin 4 (chassis ground), pin 5 (signal ground), and pin 16 (battery positive).
ISO 9141-2 and ISO 14230-4 share identical physical-layer characteristics — pin 7 K-line at 10.4 kbaud, 8N1, half-duplex, idle high at battery voltage — so the two protocols cannot be distinguished solely by examining which connector pins are populated. ISO 15765-4 CAN (pins 6 and 14) became mandatory for all new US passenger vehicles from model year 2008. The combined resistance across pins 6 and 14 will read approximately 60 ohms on a CAN-equipped vehicle due to the two 120-ohm termination resistors at each end of the bus.