The P0571 code on your 2021 Lincoln Navigator indicates a malfunction in cruise control brake switch A circuit. The brake switch signals the cruise control system to disengage when you press the brake pedal.
Brake Switch A Function
Most vehicles use dual brake switches or a multi-function switch for redundancy. Switch A provides one brake pedal signal used for cruise control cancellation. When you press the brake, this switch should signal the PCM to disengage cruise.
Navigator Cruise Control
The 2021 Lincoln Navigator features adaptive cruise control with automatic braking capability. The brake switch integration is critical—the system must know when the driver applies brakes to properly coordinate automatic and manual braking.
Switch A Malfunction Causes
The brake switch may be misadjusted, not activating when the pedal is pressed. The switch may have failed electrically. Wiring damage affects signal transmission. Connector corrosion creates poor connections. The switch plunger may be worn or sticking.
Diagnostic Steps
Use Ford IDS to monitor brake switch A signal. Press and release the brake pedal—signal should change states reliably. Check brake switch adjustment at the pedal. Test switch with a multimeter for proper contact closure. Inspect wiring and connector condition.