sound system went into the new EK today.
85A alternator, all new speaker and sub wires, amp wiring is 4g connected directly to +ve (fused of course) and battery -ve for ground.
with front channel gain turned right up (2 speakers) amp is fine.
as soon as any rear gain is turned up (1 pioneer sub) amp protect light comes on and amp cuts out.
i thought grounding problem, but seeing as its's grounded to -ve on battery i thought this should eliminate the problem.
perhaps try grounding to chassis or engine again?
Jimmy