Start narrowing down the location of the fault. Work the problem.

The first thing to do is to rule out the amp, since you can do it without tearing the dash apart. Get another line-level device, for instance a portable CD player, and plug it into the amp's RCA inputs and listen. Do the front, then plug into rear and listen again.

After that, it's time to dismantle the dash. First thing is to rule out RCA cable problems- use your portable with the cable ends at the front of the car. If it's there, then it's time to start checking the wire runs between the dash and the trunk for problems.

Then start looking at the sled and checking for wiring problems there. See if any of the wires have come undone. Also check the docking connector to make sure there's no trouble (like a bit of fuzz or something screwing up the connector pins). Double-check that the power leads were properly connected, soldered, and shrink-wrapped. Make sure the right power lead was connected to the right inputs (the ignition wire and constant-feed wires are going to the right places).

Just use your common sense: Zero in on the fault by testing at each possible failure point.

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Tony Fabris