i have a metra 70-2104 wiring harness for my pioneer avh-p4200. (i have the onstar, but went the cheap way). the harness does not tell me what the Solid Dark Blue wire is for on the metra harness. i believe it is in the top left part, 1st row, 5th one over (i think A5)

any help would be greatly appreciated

i believe it is for the amp on things, but i could be wrong

 

yeah i think thats the remote turn on wire. on my metra harness there was a list on the bag of what each wire was

 

its probably remote turn on BUT if its a metra it should be blue white. If it has both blue white and blue cap off the blue wire and forget about it. If you only have that one check too see if theres a wire on the other side of the harness. If not then cap off. If so and its pink then yes its the remote turn on wire