hd xbox 360 cable not working with hdtv

[gold84gmc]

i have an xbox 360 and have the a/v cable with regular (red/white/yellow) and the hd (green/blue/red) and my tv has both too...i try plugging the hd plugs into the tv and put the switch on the cable to hdtv and nothing shows up and theres no sound....but if i use the regular(red/white/yellow) it works...does anyone know what im doing wrong?

[frogman68]

on the remote do you have a input button ? Go thru that seems you are on video hence the yellow white and red are working.

[Irish_Alley]

to go with what frog was saying your hd might be under a like av2 but your hd might be under av1 you might have to switch that up. i have to look at mine but I'm thinking the hd doesn't use all 6 only 4 or 5 i forget. i just you my hdmi. whats your id on there?
this should help more
Steps to connect an Xbox 360 console to a high-definition TV
1.  Turn off the Xbox 360 console.
2.  Connect the audio-visual (AV) connector on the component HD AV cable to the AV port on the Xbox 360 console.
3.  Set the HDTV switch on the AV connector to HDTV.
Note Only set the switch to HDTV if the TV supports high-definition resolution, such as 480p, 720p, 1080i, or 1080p. (1080p became supported after the November 2006 Xbox LIVE update.)
4.  Connect the red, green, and blue RCA connectors on the component HD AV cable to the corresponding color input jacks on the high-definition TV. Do not use the yellow RCA composite video connector.
5.  Connect the red and white RCA audio connectors on the component HD AV cable to the corresponding colored input jacks on the HDTV. 
6.  Turn on the Xbox 360 console. From the System section, you can change your display and HDTV settings. Select the appropriate high-definition video setting for the HDTV.
it looks like you just need to unplug the yellow jack
 if that's not enough then go here http://support.xbox.com/support/en/us/nxe/kb.aspx?ID=906303&lcid=1033&category=hardware