bakelights won't come on

2002 trailblazer the brakelights don't come on, third bakelight does come on, checked fuses under hood, under back seat, and the bulbs are fine.
Can someone help. thanks

2002-2004 Chevrolet TrailBlazer, TrailBlazer EXT

2002-2004 GMC Envoy, Envoy XL

2002-2004 Oldsmobile Bravada

This bulletin is being revised to add models and procedure information and change part numbers. Please discard Corporate Bulletin Number 03-08-42-006 (Section 08 -- Body and Accessories).

A new tail lamp circuit board is now available for service use.

If normal diagnosis of a vehicle leads to a failed tail lamp bulb, inspect the bulb socket to ensure proper fit of the bulb into the socket. If the bulb is found to be loose, or if the circuit board has failed, replace both tail lamp circuit boards with the new part number from GMSPO.

The preferred tail lamp bulb to use is now supplied by Sylvania, P/N 12450108. Please note that the tail lamp bulb may have been provided by various suppliers in the past. Technicians are to replace the tail lamp circuit boards, on both sides of the vehicle, using the following procedure:

Remove the tail lamp assembly from the vehicle. Refer to the Tail Lamp Replacement procedure in SI (Document ID #730408).
Remove the tail lamp circuit board from the tail lamp assembly. Refer to the Tail Lamp Circuit Board Replacement procedure in SI (Document ID #1340883).
Inspect for loose tail lamp bulbs in the tail lamp circuit board. Replace the tail lamp bulb and the tail lamp circuit board if necessary. Refer to the Tail Lamp Bulb Replacement procedure in SI (Document ID #743430) and the Tail Lamp Circuit Board Replacement procedure in SI (Document ID #1340883).
Install the tail lamp circuit board. Refer to the Tail Lamp Circuit Board Replacement procedure in SI (Document ID #1340883).
Install the tail lamp assembly. Refer to the Tail Lamp Replacement procedure in SI (Document ID #730408).
Replace the tail lamp circuit board on the opposite side of the vehicle using the above procedure.
Verify the operation of the tail lamps.
Parts Information
Part Number
Description
Qty

16532713
Board, Tail Lamp Circuit-Chevrolet
1

16532715
Board, Tail Lamp Circuit-Oldsmobile/Buick
1

16532716
Board, Tail Lamp Circuit-GMC
1

12450108
Bulb-3157
1

thanks 99ssconv

Have you tried testing the connection with a multimeter? That might be a way of testing to see if the circuit board is getting current before buying a new one.