Hello everyone,
I have a Epic bass from 1994.
I have a problem with the neck pickup with the level output ( big difference of volume with the bridge pickup)
The bridge pickup is ok, but the neck as less level output.
The electronic is ok, battery ok, and the 2 pickups was in good place...
Can you help me?
Thanks!!!

Hi Jean, and welcome to the club.   Have you tried adjusting the trimpots in the control cavity?

Bill, the guitar one.

Well, a 94 Epic would have just one trimpot, unless it was upgraded with a Pan Preamp.

You can try unplugging the pickup leads and reconnecting them again a few times. Please check the FAQ page on the modular connectors to make sure you don't damage anything - just be gentle.

While you have the connectors unplugged, check to see if the wires are attached properly to the connectors.

Try swapping the pickup leads and see if the low output level also "swaps". That would give you an clue if there is an issue with the pickup itself or the electronics. As Adriaan has already pointed out the connections should be checked, may be as simple as a loose connection. If you have a chance post a picture of the cavity and electronics, always helpful when doing "virtual" troubleshooting. 

I the bass i have : volume, pan, treble and bass
I have try all what you said.......nothing change... i think problem with pickup.....
What do you think?

Jean,
Pickups do fail, even Alembic units, although rarely. Sending the pickup to Alembic will assure you of its condition. Keeping the other working pickup in the bass will at least keep you up and playing. As advised try moving the connectors while tapping on the problem pickup with a metal screwdriver to see if the issue might be with the external wiring between the pickup output and where it connects to the EQ circuit. Exercise the pan pot many rotations, too.

What's strange is having any output from the pickup in a failure. There's just one wire, and so it's hard for anything but that to break and when it does there's no signal. Can you measure the impedance?