Subwoofer is not playing
It is hard to say. The sub-woofer has its own amplifier, although it is supplied the sound data from the main amplifier. It could have a problem with the battery power circuit (Sub-Woofer Amplifier Connector Pin 6, LIGHT GREEN/VIOLET) or it could have a problem with the GROUND circuit (Pin 2, BLACK/LIGHT GREEN) Or it could possibly not be receiving the signal from the main amplifier (Pin 7, BROWN/ORANGE "+"), (Pin 8, RED/BLACK "-"). Or it could be that either the sub-woofer speaker is blown, or the sub-woofer amplifier is defective.
There is also a "High Audio Mute" circuit that connects between the main amplifier and the sub-woofer amplifier.