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Which OBD-II protocol is supported by vehicle?

2009-08-09 13:55:47 elm327 Read

Which OBD-II protocol is supported by vehicle?

All cars and light trucks built for sale in the United States after 1996 are required to be OBDII compliant. The European Union adopted a similar law in 2000 for gasoline-powered vehicles, and in 2003 for cars with diesel engines.


An OBD-II compliant vehicle can use any of the five communication protocols: J1850 PWM and VPW, ISO9141, ISO14230 (also known as Keyword Protocol 2000), and more recently, CAN (ISO15765/SAE J2480). Car manufacturers were not allowed to use CAN until model year 2003.

As a general rule, you can determine which protocol your vehicle is using by looking at the pinout of the DLC:

The following table explains how to determine the protocol:

Pin 2Pin 6Pin 7Pin 7Pin 14Pin 15*Standard

J1850 Bus+

CAN HighISO 9141-2K Line and
ISO/DIS 14230-4
J1850 BusCAN LowISO 9141-2L Line and
ISO/DIS 14230-4

must have--must have--J1850 PWM
must have-----J1850 VPW
--must have--may haveISO9141/14230
-must have--must have-CAN
The connector should have: Pin 4 - Chassis Ground, Pin 5 - Signal Ground, Pin 16 - Battery power

This means that:

ProtocolThe connector must have pins
PWM2, 4 and/or 5, 10, and 16
VPW2, 4 and/or 5, and 16, but not 10.
ISO4 and/or 5, 7, and 16. Pin 15 *may or may not be present.
CAN4 and/or 5, 6, 14 and 16

*For ISO communications, pin 15 (L-line) is not always required. Pin 15 was used on earlier ISO/KWP2000 cars to "wake-up" the ECU before communication could begin on pin 7 (KLine). Later cars tend to communicate using only pin 7 (K-Line).


Because of the different protocol a car might have it is recommended to use an interface which supports all protocols as all modern interfaces do.