Just bought vehicle, kenwood KDC 722 stereo wont work till enter 4 digit security code.... ANY suggestions??

You can enter a 4-digit security code as an option after purchase of the unit. If you do so, make sure it is noted down somewhere. If you did select a code (or the previous owner has done so) this must be used when the unit is removed from the vehicle, or the constant power source is disconnected from the unit. When constant power is restored to the unit, the security code must be entered before the unit becomes operational. If the code is lost or forgotten I am afraid the unit has to be re-coded by a Kenwood dealer.
Hope this helps, Good luck with it.

You can enter a 4-digit security code as an option after purchase of the unit. If you do so, make sure it is noted down somewhere. If you did select a code (or the previous owner has done so) this must be used when the unit is removed from the vehicle, or the constant power source is disconnected from the unit. When constant power is restored to the unit, the security code must be entered before the unit becomes operational. If the code is lost or forgotten I am afraid the unit has to be re-coded by a Kenwood dealer.
Hope this helps, Good luck with it.

You can enter a 4-digit security code which must be used when the unit is removed from the vehicle, or the constant power source is disconnected from the unit. When constant power is restored to the unit, the security code must be entered before the unit becomes operational.
If the code is lost or forgotten I am afraid the unit has to go to a Kenwood dealer for re-coding.

Common Kenwood Security Codes Many Kenwood radios are configured with the same security codes:

• KCAR - This seems to be a "backdoor" to some Kenwood models.
• 3051 - This is the security code which is printed in the manual of many Kenwood models.
• 1234 - This is a security code commonly chosen by Kenwood owners.

Entering Your Kenwood Security Code If the car battery fails or is disconnected, the Kenwood will ask for the security code.
The procedure to enter your security code differs on various models of Kenwood car stereos. Here are three of the more common procedures:
Type 1

• During the code request mode, while holding the DISP key depressed, press and hold the Volume UP or DOWN key for 3 seconds until the "..." display disappears.
• Enter the security code using your Kenwood remote.

Type 2

• Press the "Auto" button and "Track up" on the face of radio at the same time until the four dash lines disappear.
• Enter the security code using your Kenwood remote.

Type 3: Model# DPX-4020 and DPX-4030

• Press and hold the 1 then the 6 preset keys until the display shows the letter 'C'.
• Enter the security code using your Kenwood remote.

Entering Letters on your Kenwood Remote To enter a letter using your Kenwood remote, press a button once for the first letter, twice for the second letter, and three times for the third letter -- then press the Track Up or Next Track key to send the letter.
To send the letter 'A', press the 2 key once and then press the Track Up key. To send the letter 'B', press the 2 key twice and then press the Track up key.
Finally, when you are done entering all of the letters, press and hold the Track Up button for 3 seconds.
The key sequence to enter the security code KCAR is:

• 5
• 5
• Track Up
• 2
• 2
• 2
• Track Up
• 2
• Track Up
• 7
• 7
• Track Up

Your Kenwood should then enter tuner mode.
A Security Code Bug in some Kenwoods There is a reported bug in the security code handling of some Kenwood stereos. In models with thie bug, the security code is stored incorrectly. The workaround is to enter the wrong security code.
In models with this bug, you have to decrement the third character of the security code by one. If your security code was 1111, you would enter your security code as 1101. If your security code was 9999, you would enter 9989.

Sending Your Radio Back to Kenwood If all else fails, you can send your stereo back to Kenwood to have the security code reset.

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Common Kenwood Security Codes
Many Kenwood radios are configured with the same security codes:

KCAR - This seems to be a "backdoor" to some Kenwood models.
3051 - This is the security code which is printed in the manual of many Kenwood models.
1234 - This is a security code commonly chosen by Kenwood owners.
Entering Your Kenwood Security Code
If the car battery fails or is disconnected, the Kenwood will ask for the security code.

The procedure to enter your security code differs on various models of Kenwood car stereos. Here are three of the more common procedures:

Type 1
During the code request mode, while holding the DISP key depressed, press and hold the Volume UP or DOWN key for 3 seconds until the "..." display disappears.
Enter the security code using your Kenwood remote.
Type 2
Press the "Auto" button and "Track up" on the face of radio at the same time until the four dash lines disappear.
Enter the security code using your Kenwood remote.
Type 3: Model# DPX-4020 and DPX-4030
Press and hold the 1 then the 6 preset keys until the display shows the letter 'C'.
Enter the security code using your Kenwood remote.
Entering Letters on your Kenwood Remote
To enter a letter using your Kenwood remote, press a button once for the first letter, twice for the second letter, and three times for the third letter -- then press the Track Up or Next Track key to send the letter.

To send the letter 'A', press the 2 key once and then press the Track Up key. To send the letter 'B', press the 2 key twice and then press the Track up key.

Finally, when you are done entering all of the letters, press and hold the Track Up button for 3 seconds.

The key sequence to enter the security code KCAR is:

5
5
Track Up
2
2
2
Track Up
2
Track Up
7
7
Track Up
Your Kenwood should then enter tuner mode.

A Security Code Bug in some Kenwoods
There is a reported bug in the security code handling of some Kenwood stereos. In models with thie bug, the security code is stored incorrectly. The workaround is to enter the wrong security code.

In models with this bug, you have to decrement the third character of the security code by one. If your security code was 1111, you would enter your security code as 1101. If your security code was 9999, you would enter 9989.

Common Kenwood Security Codes
Many Kenwood radios are configured with the same security codes:

KCAR - This seems to be a "backdoor" to some Kenwood models.
3051 - This is the security code which is printed in the manual of many Kenwood models.
1234 - This is a security code commonly chosen by Kenwood owners.
Entering Your Kenwood Security Code
If the car battery fails or is disconnected, the Kenwood will ask for the security code.

The procedure to enter your security code differs on various models of Kenwood car stereos. Here are three of the more common procedures:

Type 1
During the code request mode, while holding the DISP key depressed, press and hold the Volume UP or DOWN key for 3 seconds until the "..." display disappears.
Enter the security code using your Kenwood remote.
Type 2
Press the "Auto" button and "Track up" on the face of radio at the same time until the four dash lines disappear.
Enter the security code using your Kenwood remote.
Type 3: Model# DPX-4020 and DPX-4030
Press and hold the 1 then the 6 preset keys until the display shows the letter 'C'.
Enter the security code using your Kenwood remote.
Entering Letters on your Kenwood Remote
To enter a letter using your Kenwood remote, press a button once for the first letter, twice for the second letter, and three times for the third letter -- then press the Track Up or Next Track key to send the letter.

To send the letter 'A', press the 2 key once and then press the Track Up key. To send the letter 'B', press the 2 key twice and then press the Track up key.

Finally, when you are done entering all of the letters, press and hold the Track Up button for 3 seconds.

The key sequence to enter the security code KCAR is:

5
5
Track Up
2
2
2
Track Up
2
Track Up
7
7
Track Up
Your Kenwood should then enter tuner mode.

A Security Code Bug in some Kenwoods
There is a reported bug in the security code handling of some Kenwood stereos. In models with thie bug, the security code is stored incorrectly. The workaround is to enter the wrong security code.

In models with this bug, you have to decrement the third character of the security code by one. If your security code was 1111, you would enter your security code as 1101. If your security code was 9999, you would enter 9989.

you should try the defaults 0000,0123,1234. in most cases unless you or the original owner put in the security code. Worse case it will just keep turning off till you get it right.

for your kdc-mp528 will work whith code KCAR entered from the remote

Common Kenwood Security Codes
Many Kenwood radios are configured with the same security codes:

KCAR - This seems to be a "backdoor" to some Kenwood models.
3051 - This is the security code which is printed in the manual of many Kenwood models.
1234 - This is a security code commonly chosen by Kenwood owners.
Entering Your Kenwood Security Code
If the car battery fails or is disconnected, the Kenwood will ask for the security code.

The procedure to enter your security code differs on various models of Kenwood car stereos. Here are three of the more common procedures:

Type 1
During the code request mode, while holding the DISP key depressed, press and hold the Volume UP or DOWN key for 3 seconds until the "..." display disappears.
Enter the security code using your Kenwood remote.
Type 2
Press and hold the "Auto" button and "Track up" (next track button on the right) on the face of radio at the same time until the four dash lines disappear.
Enter the security code using your Kenwood remote.
Type 3: Model# DPX-4020 and DPX-4030
Press and hold the 1 then the 6 preset keys until the display shows the letter 'C'.
Enter the security code using your Kenwood remote.
Entering Letters on your Kenwood Remote
To enter a letter using your Kenwood remote, press a button once for the first letter, twice for the second letter, and three times for the third letter -- then press the Track Up or Next Track key to send the letter.

To send the letter 'A', press the 2 key once and then press the Track Up key. To send the letter 'B', press the 2 key twice and then press the Track up key.

Finally, when you are done entering all of the letters, press and hold the Track Up button for 3 seconds.

The key sequence to enter the security code KCAR is:

5
5
Track Up
2
2
2
Track Up
2
Track Up
7
7
Track Up
Your Kenwood should then enter tuner mode.

A Security Code Bug in some Kenwoods
There is a reported bug in the security code handling of some Kenwood stereos. In models with thie bug, the security code is stored incorrectly. The workaround is to enter the wrong security code.

In models with this bug, you have to decrement the third character of the security code by one. If your security code was 1111, you would enter your security code as 1101. If your security code was 9999, you would enter 9989.

i hope this works for you.

3. Simplified method of clearing the security code
(K Type only)
1. While the code entry is requested, press and hold the
VOL UP key for 3 seconds while holding the DISP key
pressed. (This should turn "----" off.)
2. Enter "KCAR" from the remote. (Same way as the 01
model)
 Press the 5 key on the remote twice, then press the
Track Up key. (This enters "K".)
 Press the 2 key on the remote 3 times, then press
the Track Up key. (This enters "C".)
 Press the 2 key on the remote once, then press the
Track Up key. (This enters "A".)
 Press the 7 key on the remote twice, then press the
Track Up key. (This enters "R".)
3. The security code is cleared and the unit enters the
ALL OFF mode.
4. If you commit a mistake in the code entry, the unit
enters the code request mode again.

Kenwood Stereos do not have 5 digit codes. They are only a 4 digit code.