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OBD-II Protocols
An OBD2 compliant vehicle can use any of the five communication protocols: SAE J1850 PWM, SAE J1850 VPW, ISO9141-2, ISO14230-4 (KWP2000), and since 2003 also ISO 15765-4/SAE J2480. ELM-USB and OBDTester support all of them.Some websites say they support 9 or even more protocols. This is because they mistakenly count protocol variants as separate communication protocols. If you add 4 variants of CAN-BUS to our list, you are on 9.
ISO15765-4 (CAN-BUS)
The most modern protocol, mandatory for all 2008+ vehicles sold in the US. Uses pins 6 and 14, communication is differential.Four variants of ISO15765 exist. They differ only in identifier length and bus speed:
- ISO 15765-4 CAN (11 bit ID,500 Kbaud)
- ISO 15765-4 CAN (29 bit ID,500 Kbaud)
- ISO 15765-4 CAN (11 bit ID,250 Kbaud)
- ISO 15765-4 CAN (29 bit ID,250 Kbaud)
ISO14230-4 (KWP2000)
Very common protocol for 2003+ vehicles using ISO9141 K-Line. Uses pin 7.Two variants of ISO14230-4 exist. They differ only in method of communication initialization. All use 10400 bits per second.
- ISO 14230-4 KWP (5 baud init,10.4 Kbaud)
- ISO 14230-4 KWP (fast init,10.4 Kbaud)
ISO9141-2
Older protocol used mostly on European vehicles between 2000 and 2004. Uses pins 7 and optinally 15.SAE J1850 VPW
Diagnostic bus used mostly on GM vehicles. Uses pin 1, communication speed is 10.4 kB/sec.SAE J1850 PWM
Diagnostic bus/protocol used mostly on Ford. Uses pins 1 and 2, communication signal is differential and it's rate is 41.6kB/sec.Determining protocol from OBD-2 pinout
As a general rule, you can determine which protocol your vehicle is using by looking at the pinout of the OBD-II connector:
| Standard | Pin 2 | Pin 6 | Pin 7 | Pin 10 | Pin 14 | Pin 15 |
|---|---|---|---|---|---|---|
| J1850 PWM | must have | - | - | must have | - | - |
| J1850 VPW | must have | - | - | - | - | - |
| ISO9141/14230 | - | - | must have | - | - | optional |
| ISO15765 (CAN) | - | must have | - | - | must have | - |