C1291: OBD-II code C1291 flags open brake lamp switch contacts during deceleration — the EBCM saw the vehicle slowing but never saw the brake pedal pressed.

Symptoms

• ABS and stability control warning lamps may illuminate; the code often sets after a hard braking event.
• Brake lights may fail to illuminate when the pedal is pressed, since the switch is failing to close.
• Cruise control may not disengage on pedal press, and TCS/ESC interventions can behave unpredictably.

Common causes

• A failed brake lamp switch with worn or oxidised contacts that no longer close reliably when the pedal is pressed.
• An out-of-adjustment brake pedal switch bracket that lets the plunger drift too far from the pedal arm.
• Damaged or corroded wiring or connector at the brake pedal switch causing an intermittent open in the switch feed.

What to do?

Test brake lamp switch continuity with the pedal released and pressed — the switch should close cleanly when pressed. Verify brake lights illuminate when the pedal is depressed. Adjust the switch bracket to spec, or replace the switch if it is out of tolerance.