OBD-II connector pinout

The 16-pin diagnostic connector fitted to essentially every modern vehicle (SAE J1962). It is often the quickest place to reach a vehicle's CAN bus, and the resistance check for termination is easiest here.

The four pins that matter

For a CAN connection you need these and nothing else:

Pin Function
6 CAN High
14 CAN Low
4 or 5 Ground — chassis (4) or signal (5)
16 Permanent battery positive (KL30)

Pin 16 is live with the ignition off. It is a permanent supply straight from the battery, usually only modestly fused. Treat it accordingly.

Full connector

Viewed looking into the vehicle-side socket, pin 1 is top-left of the wider row, numbering left to right, top row then bottom row.

Pin Function Pin Function
1 Manufacturer discretion 9 Manufacturer discretion
2 SAE J1850 bus + 10 SAE J1850 bus −
3 Manufacturer discretion 11 Manufacturer discretion
4 Chassis ground 12 Manufacturer discretion
5 Signal ground 13 Manufacturer discretion
6 CAN High (ISO 15765-4) 14 CAN Low (ISO 15765-4)
7 K-line (ISO 9141-2 / KWP2000) 15 L-line (ISO 9141-2)
8 Manufacturer discretion 16 Battery positive

Pins marked manufacturer discretion are exactly that — a second CAN bus, a proprietary network, or nothing at all, depending on the vehicle. Do not assume a pin is unused because the standard does not assign it.

Using it on a swap

The connector is standard; what is behind it is not. On a car that has been stripped or rewired, pins 6 and 14 may reach nothing, or may reach a different bus than you expect. Confirm before relying on it:

  • Power off, measure pin 6 to pin 14. Around 60 Ω means you have found a correctly terminated bus. ~120 Ω means one terminator; open means you are not on a live bus at all.
  • Power on, measure each to ground. Both near 2.5 V is a healthy idle bus.

Both checks, and what other readings mean, are on CAN Bus Diagnostics.