Thanks guys. Just found out the problem is that the head unit is searching for the 2008 4runners ESN number. So I have a bypass harness on the way. Ill let you know what happens when I get it installed. Apparently its a theft deterrent.
Who told you that BS about the ESNs??? The OEM navs don't have the ESN security. Only Eclipse radios had the ESNs. I've had the E7006, 7007, E7008, E7009, and then another E7008 (in that order, over quite a few years) in my 2003 Limited, and electrically, the only thing I had to do was run a twisted pair wire to the amp from the head unit for voice, and add the right side switch bank on the steering wheel for BT & voice functions. Oh, and I added the mic of course, and rear camera.
The E7006 can use the amp installed in the 2003 without a problem. If you install a 7007, 7008, or 7009, you will need a newer style amp as the signal is digital. Believe me - you get some odd actions with the older amp & newer nav. Sometimes it works, sometimes it doesn't. Sometimes it goes full volume! You will need the newer amp.
I just so happen to have both amps for sale in the for sale section.
This first picture is of the back of an E7007 nav unit. The E7008 will be the same.
I made this pinout diagram several years ago, and have seen it reposted a few times since. Nice to know it's been useful.
