All Speakers Inoperative with Remote Amplifier-UZ6

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

Important: The following information lists the most probable cause of the concern to the least probable cause followed by the appropriate test for that condition. If the list leads to the replacement of a component, always inspect for a poor connection before proceeding with the replacement. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems.

Test the battery and ground supply circuits to the amplifier. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Test the sensitivity and mute circuits for an open or short to ground condition. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
No audio output from the radio. Replace the radio. Refer to RADIO REPLACEMENT .
No audio output from the amplifier. Test for any AC voltage between one speaker output circuit at the amplifier with the appropriate speaker disconnected and the radio volume adjusted to an audible level. If no AC voltage is present at the amplifier, replace the amplifier.