The radio takes a 4 digit code entry but older radios used a 6 digit. The system the dealer uses to get codes has provosions for the six digit code and when a four digit is appropriate it fills in the first two places with zeroes. Use the four digits and ignore the two zeroes. If you make an error and the dispaly says "ERR" then you will need to leave radio on for two hours before it will let you have another opportunity (leave it in key pos. I).