Borrowed from autotap faq...
Your vehicle must have an OBD II connector that looks like this:
and has pin combinations representing one of the four OBD II protocols:
J1850 VPW – The connector will have metallic contacts in pins 2, 4, 5, and 16, but not 10.
ISO 9141-2 – The connector will have metallic contacts in pins 4, 5, 7, 15, and 16.
J1850 PWM – The connector will have metallic contacts in pins 2, 4, 5, 10, and 16.
KWP2000 (ISO142300) – The connector will have metallic contacts in pins 4, 5, 7, 15, and 16.
The pins are used in the following way:
Pin 2 - J1850 Bus+
Pin 4 - Chassis Ground
Pin 5 - Signal Ground
Pin 6 - CAN High (J-2284)
Pin 7 - ISO 9141-2 K Line and ISO/DIS 14230-4
Pin 10 - J1850 Bus
Pin 14 - CAN Low (J-2284)
Pin 15 - ISO 9141-2 L Line and ISO/DIS 14230-4
Pin 16 - Battery Power
If your connector has extra pins, don’t worry. Manufacturers can use them as they see fit.
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