Thanks for your patience.
There are two possible codes, depending on which radio model you have. You have two options here; you can pull the radio to verify the model number on the sticker on the chassis, or if you have NOT attempted to input a code yet, you can just try both. The radio allows 3 attempts at code entry, so with only two possibilities you will have no problem if you have not had any failed attempts yet.
If your radio is model MR472956 the code is 9718
If your radio is model MR490089 the code is 8329
To input the code, use the preset buttons to scroll through the digits.
Pressing preset button 1 will scroll the first digit (0---, 1---, 2---, etc) until it reaches 9
Pressing preset button 2 will scroll the second digit (90--, 91--, 92--, etc) until it reaches 97
And so forth with preset 3 and 4 for the third and fourth digits.
Once the code is displayed correctly, push the unlock button. This button is different on each radio but is always either CD, AMFM or TAPE. There is no penalty for a wrong button if the code is displayed correctly, so just push each one once. If the code is correct it will beep and unlock. If the code is wrong it will say Err1 and give you another chance. Use the second code if this happens.
If you fail 3 times, the radio will display "oFF" and the key must be left in the on position for 75 minutes to return the radio to the code screen.