Dashboard removal in a GMC Sonoma can be a tricky task, though not a mechanically demanding one. It requires patient locating of a number of small, hidden screws and dealing with many electrical connectors. The most common reason for removing the Sonoma dashboard is the routine repair of a leaky heater core, which is mounted on the firewall immediately behind the dash.
Take out the left and right lower dash panels, each secured by two Torx screws and two clips. Locate the large vertical mounting bolts on the bottom of the dashboard. Remove the the dashboard pivot bracket with a socket on an extender. Now remove the two Torx bolts immediately adjacent to the pivot bracket.
Remove the four bolts securing the steering column to the dash and firewall bracket with a socket wrench. Lower the steering column. With a socket on an extender, remove the single "pencil brace" bolt under the dash just to the right of center.
Pry up the speaker grilles and the defroster grille to reveal the upper dashboard mounting bolts hidden underneath. Using a socket on an extender, remove all bolts.
Pivot the dash to the rear, exposing the cables that must be disconnected. Tag both ends of each cable with numbered masking tape to make reassembly easier. Reach around from the right side of the dash and disconnect the main electrical wiring harness. Reach behind the center of the dash and disconnect the radio antenna lead. The dashboard can now be pulled completely away from the firewall and the heater core accessed. Installation is the reverse of removal. Take care to make sure the electrical connections are correct and that the connectors fully engage.
