Same thing happened to me with an Alpine head unit. Pull the unit and get the serial number off of it, contact Kenwood support, better by phone, give them the serial number and they should have the unlock code for that unit. Each head unit is different on how to enter the code, If you have the manual for it, it will be there. Here is the procedure for entering the code. Below is also the link for your service and setup manual.
http://manual.kenwood.com/files/B64-2695-00.pdf
Security Code
Because authorization by the Security Code is
required when it’s removed from the vehicle,
personalizing this unit is by using the Security
Code is a help in preventing theft.
• When the Security Code function is activated, the code
can’t be changed and the function can’t be released.
Note, the Security Code can be set as the 4 digit number
of your choice.
1 Enter Standby
Press the [SRC] button.
Select the "STANDBY" display.
2 Enter Menu mode
Press the [MENU] button for at least 1 second.
When "MENU" is displayed, "Security" is displayed.
3 Enter Security Code mode
Press the [4
] or [¢
] button for at least 1
second.
When "ENTER" is displayed, "CODE" is displayed.
4 Select the digits to enter
Press the [4
] or [¢
] button.
5 Select the Security Code numbers
Press the [FM] or [AM] button.
6 Repeat steps 4 and 5, and complete the
Security Code.
7 Confirm the Security Code
Press the [¢
] button for at least 3 seconds.
When "RE-ENTER" is displayed, "CODE" is
displayed.
8 Do the step 4 through 7 operation, and
reenter the Security Code.
"APPROVED" is displayed.
The Security Code function activates.
• When the wrong Code is entered in steps 4 through 6,
repeat from step 4.
Press the Reset button and when it’s removed
from the battery power source
1 Turn the power ON.
2 Do the step 4 through 7 operation, and enter
the Security Code.
"APPROVED" is displayed.
