2001 Oldsmobile Alero Service Vehicle Soon.
Question: Why does my left and right brake lights don't work but the middle brake light does?
There doesn't appear to be any blown bulbs or fuses.
The high mount stop lamp is on a different circuit than the left and right brake lamp as it come out of the left fuse dash fuse/junction block. It is possible that you have a bad connection within or on the back side of that block for the wires that run to the brake lamps.
Since you did not leave the model year, i went with a 2001 Alero. These blocks have a tendency to get corroded by water intrusion. It may show signs of water intrusion by removing several fuses and look for signs of dried up water/rust, also on the back side of the block where all the wires come out. This condition is probably the reason for the service vehicle light on the dash. But cant be sure unless have the BCM (Body Control Module scanned for codes.
2001 Chevy Venture van.
Driver side turn signal works fine when the brake is NOT applied. As soon as brake is applied, turn signal flashes very fast. Also related, when cruise control is on and as soon as you turn on the driver side turn signal it turns the cruise control off.
Also related, when in reverse, the driver side turn signal does not work at all. Tried replacing the bulbs and didn't work. Autozone suggested replacing the Brake light Switch.
As long as the bulbs that were replaced were the proper type, then this sounds like a problem in the driver side rear lamp circuit board assembly. Sometimes the connector gets corroded, or the board shorts out internally, causing all kinds of odd lighting problems, shorting out, open circuits, back feeding. Try swapping the entire assembly with the pass. side, and see if the problems follow. If they do, then you have a problem in that board.
Brake Light And Turn Signal Problems