The P0504 code on your 2019 Nissan Altima typically indicates a correlation error between brake switch inputs. Many vehicles use dual brake switches for redundancy, and P0504 sets when these switches disagree about brake pedal position.
Brake Switch Redundancy
Modern vehicles often use two brake switches or a multi-function switch with redundant circuits. One circuit controls brake lights while another signals the ECM for cruise control disengagement, shift interlock, and other functions. P0504 indicates these circuits are providing conflicting information.
Altima Brake Switch System
The 2019 Altima's brake switch system integrates with cruise control, shift lock release, and brake light operation. The ECM monitors both brake switch inputs—when they don't agree (one says brake pressed, one says not pressed), P0504 sets.
Causes of Switch Correlation Errors
The brake switch may be misadjusted. One switch element may have failed while the other works. Connector issues may affect one circuit but not the other. The switch plunger may be sticking intermittently. Wiring damage to one switch circuit creates disagreement.
Diagnostic Steps
Use Nissan Consult to monitor both brake switch inputs simultaneously. Press and release the pedal while watching both signals. Check brake switch adjustment—it should activate at the proper pedal position. Inspect the switch connector and wiring. Test each switch circuit independently.