OBD-II signal protocols

 An OBD2 vehicle of can use one or more of the five communication protocols: SAE J1850 PWM, SAE J1850 VPW, ISO9141-2, ISO14230-4 (KWP2000) and ISO 15765 CAN (250 kBit/s or 500 kBit/s). Most vehicles implement only one of the protocols. Manufactures can deduce the protocol used based on which pins are present on the J1962 connector:
1.      SAE J1850 PWM
This diagnostic bus/protocol is used mostly on Ford, using pin 2 and pin 10.
2.      SAE J1850 VPW
This diagnostic bus is used mostly on GM vehicles, using pin 2, communication speed is 10.4 kB/sec.
3.      ISO 9141-2.
This protocol has an asynchronous serial data rate of 10.4 kBaud. It is an older protocol used mostly on Chrysler, European and Asian vehicles between 2000 and 2004. It adopts pins 7 and sometimes 15.
4.      ISO 14230 KWP2000 (Keyword Protocol 2000)
This protocol is very commonly used on 2003+ vehicles using ISO9141 K-Line. It adopts pin 7 and optional pin 15.
5.      ISO 15765 CAN
This protocol was developed by Bosch for automotive and industrial control. Different from the four OBD protocols mentioned above, variants are widely used outside of the automotive industry. Since 2008, the protocol is applied to all vehicles sold in the US. It uses pin 6 and pin 14.