Ryan Compton:

Tapping into your car’s ECU is surprisingly easy
 All cars sold in North America since 1996 are required to support OBD-II diagnostics with standardized data link connectors and parameter IDs. This is useful, for example, for state-mandated emissions inspections. The OBDII port looks a bit like a VGA connector and, on my car (a 2003 Suzuki Aerio SX), is located under the dash and just above the accelerator.