Code 81 - Brake Switch Error (3.4L "F" Body): Notes
WARNING: This page is about a different car, the 1993 Pontiac Grand Prix, 1993 Pontiac Firebird, 1993 Oldsmobile Cutlass Supreme, 1993 Chevrolet Lumina, and 1993 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
ECM monitors the status of the brake switch circuit through the TCC/brake switch input. Code 81 will set if the vehicle speed has been greater than or equal to 35 MPH for 10 seconds and back to zero MPH for at least 4 occurrences and status of TCC/brake switch input has not changed from applied to release or released to applied as indicated on scan tester.