OBD 2 and CAN Protocol VAG-Com

OBD2 Scanner On board diagnostic 2nd revision started in the state of california by the California Air Resources Board CARB.
Mandated by the EPA in 1996 All cars 1996 and newer require this connector All connectors are the same for every vehicle generic connector, you need a special scan tool to connect to this generic connector.

Scan tool reads data from the computer, o2 lean/rich info, MAP sensor Data, Throttle Position, Fuel Vag Com Usb Kkl Interface Trim, Trouble codes, Misfire data, evap leak detection, etc.
Some scan tools read data codes only. Other scan tools can read data also as mentioned above, we will go over specific trouble codes in a different article.
Obd 2 uses special language called a protocol to communicate with a scan tool. OBD2 has nine different protocols, they are produced by Society of Automotive Engineers in the USA and the International Standards Organization based in the European Union

All vehicles 2008 and newer need to speak CAN (Controlled Area Network) protocol  it is a much faster protocol its simply an agreement for communication interchange
CAN  protocol it the VAG-Com  most important protocol

The 16 pim generic connector  description:
Reserved for OEM Comm.

1. Reserved for OEM Comm.
2. Comm Bus + Square Wave Signal
3. OEM Reserved
4. Chassis Ground
5. Sensor Ground
6. OEM Comm
7. Comm Bus Negative
8. 11 12 13 14 VAG-Com   OEM Reserved
9. L Line ISO and 9141 Protocol
10. unswitched battery power

Used as a diagnostic tool:Pin 4 can be used to test the vehicles grounding system Pin 5 tells you if the ECU is grounded properly Pin 16 allows you to test all power feed components If no communication with the ECM look at pin 16, could be a blown fuse. Pin 4 is uobd2  connected straight to the chassis. Pin 5 goes through the ECM and is tied to most vehicle sensors. Pin 16 is usually connected to steady power fuse box and battery.