For models equipped with the standard factory sound system, locate the 18-pin connector behind the head unit–it’s typically black and marked with alphanumeric labels B, C, D, E, F,.

Replace factory speakers or install an aftermarket head unit in this mid-size truck model? Start by tracing the 14-pin harness behind the dash. Pin 1 (red) delivers constant 12V.

Connect the head unit’s yellow (constant 12V) wire directly to the battery’s positive terminal using a 4-gauge fuse holder within 18 inches of the battery. Skip factory harness splices–these.

The 2003–2009 model lineup’s speaker harness uses a 14-pin rectangular connector (AMP 1718441 or equivalent). Pin assignments follow this layout: pins 1–4 (front door speakers), pins 5–8 (rear doors),.