I'm attempting to install a new stereo head unit into my 1998 Honda Civic EX. I have the proper adapters, and all the wires are connected properly. However, when I hook everything up, the head unit won't power up. I've got the green "keyless entry" connector hooked up to the back of the old stock receiver, and the adapter piece connected to the back of the stock receiver as well.

My question is, there seems to be another green connector that's not hooked up to anything. Perhaps it came loose in all of the tugging around trying to get things connected? Where is this connector supposed to go?

I'm trying to get this fixed before this weekend, about to go on a 6 hour trip and would love to have my system up and running!

 

The power comes through the big main connector. The keyless stuff is just for the keyless system. There are two fuses involved. Power for the "constant on" wire (yellow wire on aftermarket radios; white with blue stripe in the Honda harness) comes from the "BACK UP" fuse in the box under the hood near the battery.

Note that the stock radio gets almost all its power from the ignition circuit instead. If the constant on circuit is lost, it will still play though it will forget all settings with the key off. Aftermarket radios typically get all power from the constant on circuit and use the ignition circuit as a signal to switch on and off. Both circuits must be live or it will not play at all.

Also many aftermarket radios will not power up if they detect a short in any of the speaker wiring. If you confirm the car is supplying power to the yellow wire and the red wire, and the black wire is grounded, remove the unit from the car and bench test it with all speaker wires disconnected.