The flat plastic ribbon wire is what MartinSR is talking about.It runs under the carpet to the trunk, behind the back seat, then splits off to the taillamps. One orange and one white wire split from behind the back seat and run to the lamps, which I presume are in the sail panels in the back.
My experience is the ribbon wire is usually good EXCEPT where it plugs into the connector at the bottom of the fuse box. The orange wire is allways hot, so electrolosis takes its toll on it right at the connection at the fuse box.
Seen it on A bodys plenty of times.Just sayin
Fact is stranger than Fiction