Car Stereos: Pioneer DEH-P5000UB install, jbl system, pioneer deh

Question
I'm in the midst of installing the Pioner steroo in a highlander with the JBL amp sound system.    The front speak hookup appears to be working fine, however when I hook up any speakers to the RCA plug type connectors on the back of the stereo, I only get crackling (very faint).  So essientially only the front speakers are working.   I purchased a Harness to make it easier,  so I suspect there is something I'm missing or it's the wrong harness.

Answer
Hi Bram,

The harness you use should be different based on the existence of your JBL system.  If the aftermarket harness you bought doesn't include RCA outputs, then you have the wrong one and it won't work right without bypassing the OEM amp entirely.

Justin