Mazda 6 Mk3 diagnostic port or OBD2 port is shown in the picture below. The diagnostic port is used for diagnosing faults and communicating with the vehicle. Common problems with the Mazda 6 Mk3 which need to be diagnosed are ABS lights, SRS airbag lights or engine faults and EML or MIL lights. Use the diagnostic port as shown below with a code reader to find the faults.