Code retrieval can be accessed by the ignition key or by a diagnostic readout box(DRB).To obtain the codes using the key method,set the park brake,and put the vehicle in Park/neutral.
Some 95 and later OBDII vehicles, you may be able to retrieve OBDII codes with this procedure, if equipped with digital dash.

Turn the ignition key ON,OFF,ON,OFF,and finally ON again(ENGINE NOT RUNNING)
The codes will start to flash on the POWER LOSS or CHECK ENGINE light.
FLASH,pause,FLASH,FLASH=code 12