2005 Chevrolet Malibu PO573 Fault: Brake Switch A Circuit High - Cruise Control & Third Brake Light Issues

Model: chevy malibu Fault Code: P0573 Posted: 2023-01-17 20:57

Hi, I own a 2005 Chevrolet Malibu with a 2.2L engine and recently encountered Diagnostic Trouble Code (DTC) PO573 — 'Brake Switch A Circuit High'. This code is triggering issues with my cruise control system and third brake light behavior. Specifically: The cruise control does not function properly, and the third brake light only works when the key is in the 'Accessories' position. As soon as I turn the key to 'On' or start the engine, the third brake light stops working entirely. This behavior seems inconsistent — why would the third brake light work with the ignition in Accessories but not when the vehicle is running? Is this a fault of the brake switch (pedal-activated), the cruise control switch, or something else in the circuit? And what's the correct troubleshooting order? I've tried searching for free wiring diagrams online without success. Any guidance on diagnosing and fixing PO573 on a 2005 Malibu would be greatly appreciated.