Don't know if the radio instructions on my "99 SL500 are the same as on your '97 SL500. On my '99 after you enter the five digit code on the alpha -numeric keypad you confirm same by pressing the "OK" key. If an incorrect code is entered three times,"WAIT" will appear on the display and the radio will be locked out for about 10 minutes.Note: The lock out time will only count down if the radio is left switched on.