Where is the aux cord supose to plug in at. I have a kenwood car stereo kdc-mp4335u

SOURCE: kenwood KDC-MP5028

with the unit in standby, press the menu key, use the joystick control to choose aux, and set the aux option to "on"...then press menu again to save...when you next switch on the unit, using the SRC button you can cycle through the available options...cd - tuner - aux..etc etc

SOURCE: aux location

There is a RCA cable that comes off the back of the radio and also another cable for 3.5mm (mini-stereo jack) that also comes off the back of the radio. The RCA jacks can be used for "AUX" or "Sub-woofer" and the 3.5mm jack is just for "AUX". Your ipod can use the audio output jack or the headphone jack and plug that into the 3.5 mm jack on the back of the radio. You will need a "3.5mm male" to "3.5mm male" stereo cord that can be purchased at Radio Shack or Best Buy. Then you select "AUX" on the display with the source button to listen to it. You may need to go into the menu and activate the "AUX" input. Check your owners manual for details.

SOURCE: Can;t play my Ipod through Kenwood KDC 237

i was just having this same problem but i pressed standby and menu and scrolled up till i got to a AUH which is off all i did was turn it on and press standby again and my ipod started playing

SOURCE: ipos nano 3

It will work bu tonly after enabling the aux jack.
Place unit in standby mode then press menu for a second and then goto aux and select it to aux on1

SOURCE: no lock code for car stereo

Here you go buddy:
http://www.fixya.com/support/r538828-security_unlock_code_kenwood_most_models