Got same issue with 2001 honda accord EX [I know it is old ]
Physical key works when insert and open the trunk, but not via remote button. All other remote buttons function well.
I was searching around the forum and found the following wiring pic is identical to the wiring of this trunk.
I tested DCV on the following wire pairs. Let me know anything else I shall test. thanks
1) black/silver + blue/silver - 11V, when double clicking on the remote, this voltage can shift between 10-11V.
2) black/brown + orange, ~11V, very stable.
3) black/brown + white/red, 0V.

Not sure if 3) means the solenoid is bad? Sure I test blue/silver + orange as well?
Trunk light doesnot work as well.

I am not sure what are those and hence donot wanna short anything. thanks

 

Do you have a second remote to try to rule out a bad switch on the remote?

The wire colors don't match my 98-02 accord shop manual pdf, but the wire locations do match. Are the wire colors the same on the other side of the harness not shown in the picture?

Wht/Red is + for the trunk latch motor. Blk/Brn is - for the trunk latch motor to G601. Both of these work, because you can get the trunk to unlock with the key. They should be thicker wires.

Your issue almost has to be with the other wires or the remote. Does the instrument cluster show the trunk is open or closed?

Blu/Gry is + for the trunk open/closed latch switch. Blk/Gry is - for the trunk open/closed latch switch. Orn/Gry is + for the trunk open/closed switch for the trunk light and the instrument cluster trunk open light.

The first test is to test harness side that is coming from inside the car. You will test for 12V on two wires (blu/gry and orn/gry with the key in the II position. Your red volt meter lead will be on the wire you are testing. Your black volt meter lead will be touching a bare metal bolt somewhere inside the trunk for a good ground. Let us know what reading you get on those two wires.