if the unit is in protect mode then there may be the possibility that the speaker wires may have a short circuit in them or that the amplifier section may be damaged....you can remove the radio from it's sleeve and check the wiring behind the unit...this also would have to be done to see the model number and serial number...it should be on either the top or bottom of the unit...the speaker wires for this unit are the white, gray, green, and violet...each with another of the same color but has a black stripe in it...the black stripe is the negative side of the speaker wire....you can disconnect these wires, then turn on the unit to see if it comes out of protect mode...if it does, then there is either a bad wire somewhere in the car or a bad speaker...if the unit stays in the protect mode, then you will have to take the unit in for repair, as this indicates a circuit failure
In order for you to unlock this, you will need the key for it. There are some default keys to unlock these, but they are not widely known. I would attempt to contact the person who sold you the CD player and ask them about it.
To reset a Kenwood 8070 receiver without a remote, you typically need to locate the reset button on the device itself. This button is often small and recessed, so you may need a paperclip or a similar tool to press it. Consult the user manual or look for the reset button near the power or input/output ports on the receiver. Once located, press and hold the reset button for a few seconds until you see the receiver reset. Keep in mind that this process may vary slightly depending on the specific model of the Kenwood 8070 receiver.
Take a look at this manual diagram. https://www.manualslib.com/manual/359815/Kenwood-Ksc-Sw10.html?page=5#manual
Given the above is not your model, at least it shows the 10 pin. Ironically, below I offer a diagram of your model. The irony comes in the fact that the diagram appears labeled in Japanese But if you compare the two diagrams, maybe something will make sense from the one with the English labels. Otherwise, you might fire off a query to Kenwood customer support. https://www.manualscenter.com/manuals/kenwood/kscsw900-owner-manual.html
Here is a 10 pin harness compatible with the subwoofer. Kenwood Subwoofer Amp KSC Wa100 Wa80 Sw10 10 Pin Harness for sale online ' eBay
I don't have any information on how to power supply a kCSWA900 Kenwood subwoofer. However, I can tell you that the Kenwood KSC-SW10 compact powered subwoofer has a built-in amplifier with a 38 watts RMS power and a wired remote for control over volume level, variable low-pass crossover (50-120 Hz), and selectable phase control (0°, 180°) . The subwoofer comes with a power/ground wiring harness and preamp (RCA) and speaker-level inputs .
