Some specifications

The OBD-2 bus is a standardised data bus.
Underneath you can find an overview of different connectors as used for OBD-II diagnostic systems.

OBD-II Connector, J1962

Diagnostic connector (female) of the car:

Pin-No.	Description
1	Manufacturer mandated
2	J1850 Bus+
3	Manufacturer mandated
4	Car ground
5	Signal ground
6	CAN High (J-2284)
7	ISO 9141-2 K output
8	Manufacturer mandated
9	Manufacturer mandated
10	J1850 Bus
11	Manufacturer mandated
12	Manufacturer mandated
13	Manufacturer mandated
14	CAN Low (J-2284)
15	ISO 9141-2 L output
16	Battery (+) voltage

Used pins of the connector shows kind of protocol:

Pin (Signal)	Pin (Masse)	Pin (Signal)	Pin (Signal)	Pin (+12 V)	Protocol
--	4 + 5	7	15 *)	16	ISO 9141-2
2	4 + 5	--	10	16	PWM J1850
2	4 + 5	--	--	16	VPW J1850
--	4 + 5	6	14	16	CAN Bus

• *) Pin 15 only for older ISO 9141 implementations
• all other pins are manufacturer reserved and not used for standard OBD-II

Diagnostic connector (male) of diagnostic tool:

Contact usage of some manufacturers:

Pin	SAE J1979, ISO 15031	GM	Fiat	Opel	Saab	Isuzu	GM-LAN since 5.2002
1	Manufacturer mandated	second UART	ABS, Brakes, K-Line	reserved	Saab Instruments (+)	SIR (GM8192 Prot.)	SW-LS-CAN (33kB) or DW-FT-CAN (+) (<125kb)
2	J1850 (+) PWM/VPW	J1850(+) VPW	DW-FT-CAN(+)	n/a	n/a	n/a	n/a
3	Manufacturer mandated	Comfort	Airbag	K-Line, K2, TCM, Sunroof, CDL, Multi-Timer	n/a	ABS (KW81-Prot.)	MS-CAN (+) (95kB)
4	Chassis ground	Chassis ground	Chassis ground	Chassis ground	Chassis ground	Chassis ground	Chassis ground
5	Signal ground	Signal ground	Signal ground	Signal ground	Signal ground	Signal ground	Signal ground
6	ISO 15765 HS-CAN (+)	PCM	ISO 15765 HS-CAN(+)	Blinkcode	Blinkcode	TCM	ISO 15765 HS-CAN (+) (500kB)
7	ISO 9141 K-Line	n/a	ISO 9141 K-Line (engine)	K-Line, K1 (engine)	K-Line, K1 (engine)	K-Linie, K1 (engine)	n/a
8	Manufacturer mandated	CCM	n/a	K-Line, K4	K-Line (Saab 9000/1, KW81/82 Prot.)	n/a	reserved
9	Manufacturer mandated	first UART	Body ECU	reserved	Saab Instruments (-)	ECM/TCM (GM8192 Prot.)	DW-FT-CAN (-) (<125kb)
10	J1850 (-) PWM	n/a	DW-FT-CAN (-)	n/a	n/a	n/a	n/a
11	Manufacturer mandated	EVA Controller	(Anti-Theft system)	reserved	L-Line Memory Seats	SIR	MS-CAN (-) (95kB)
12	Manufacturer mandated	ABS	engine compartment	K-Line, K3, ABS, TC, Steering, RTD, OW	n/a	ABS	K-Line (KW82 Prot.)
13	Manufacturer mandated	SIR	Luggage compartment	reserved f. K-Line, K5	n/a	ECM	reserved
14	ISO 15765 HS-CAN (-)	E&C	ISO 15765 HS-CAN (-)	reserved	n/a	n/a	ISO 15765 HS-CAN (-) (500kB)
15	ISO 9141 L-Line	n/a	n/a	n/a	n/a	n/a	n/a
16	Battery Plus, unswitched	Battery Plus, unswitched	Battery Plus, unswitched	Battery Plus, unswitched	Battery Plus, unswitched	Battery Plus, unswitched	Battery Plus, unswitched

Internal contacting Patch-Connector OBD2/RJ45

OBD-II (male) / RJ45 female

OBD-II Pin	Description	RJ45-Pin
2	J1850 Bus+	6
4, 5	Ground	1
6	CAN-Bus	7
7	ISO 9141-2 K-output	4
10	J1850 Bus	3
14	CAN-Bus	8
15	ISO 9141-2 L-output	5
16	Battery +12V	2

OBD-II (female) / RJ45 female

OBD-II Pin	Description	RJ45-Pin
2	J1850 Bus+	6
4, 5	Ground	1
6	CAN-Bus	7
7	ISO 9141-2 K-output	4
10	J1850 Bus	3
14	CAN-Bus	8
15	ISO 9141-2 L-output	5
16	Battery +12V	2

OBD-II Cabel connection (for interfaces)

OBD-Pin Description DB9-Pin 5 Signal ground 1 4 Chassis ground 2 6 CAN High (J-2284) 3 7 ISO 9141-2 K-output 4 14 CAN Low (J-2284) 5 10 J1850 Bus 6 2 J1850 Bus+ 7 15 ISO 9141-2 L-output 8 16 Battery +12V 9