metra harness 70-8113 with 4 rca to aftermarket headunit with 6 rca?

I have a 2001 Toyota Avalon xls, with the 6 Jbl speakers, factory amplifier, and factory subwoofer. CD player did not work in oem radio; replaced, using metra 70-8113 adapter to keep factory amp and subwoofer with a kenwood kdc-152 headunit, which works great, except now its cd playing has stopped sucking in or spitting out cds. Therefore, I am attempting to replace the kenwood kdc-152 with a pioneer deh-x6700bs, using same metra adapter, though a new version, but have run into problems. First, the kenwood had 2 rca inputs and y-adapters allowed the harness with 4 rca plugs to plug into the kenwood. The pioneer has 6 rca inputs, 2 rear, 2 front, and 2 subwoofer. Nothing tells me how to plug the 4 rca plugs on the harness into the 6 rca inputs on the pioneer?

That is problem 1: metra adapter 70-8113 has 4 rca plugs ( gray for right front, white for left front, purple for right rear, and green for left rear. Pioneer deh-x6700bs has 6 rca inputs (rear right and rear left on back of head unit, with front right and front left below them, and 2 subwoofer rca inputs below them), and I don’t know which plug goes to which input to get sound out of all 6 speakers and the subwoofer?

Problem 2 is that not knowing the answer to problem 1, I have tried every combination and not had success, either meaning I am wiring wrong or something internal to the radio is not working. One combination using y adapters to plug all 4 rcas on adapter to the 2 subwoofer rcas only will give me sound out of 4-6 speakers but not the subwoofer and sound is distant and muffled, another combination not using y adapters, with 2 rcas to front and rear wires to subwoofer rca inputs on pioneer headunit gives great clear sound out of all front but no rear or subwoofer, another combination not using pioneer headunit subwoofer rcas at all gives great clear sound out of 4 door speakers but not the front dash speakers or subwoofer. I do not know if this implies an internal headunit problem? If so, who repairs aftermarket radios?

Additionally, I have read that a speaker wire touching a ground could damage the internal headunit amplifier. I believe some touching of one of the speaker wires took place, causing an amp error message on headunit. I since then fixed that wire and have not had any more amp error messages, but did not know if that could be connected to my problems, or if hearing any sound would imply that the headunit internal amp is probably fine?

Any help would be appreciated.

Thanks. Jimmy