P0504 on Nissan: How to Diagnose & Fix
Brake Switch "A"/"B" Correlation
1 Nissan model · 1 documented issue · 1 critical
P0504 on Nissan by model: symptoms, diagnosis and fix
The stop-lamp (brake light) switch becomes contaminated by silicone off-gassing from grease used on nearby components. Electrical arcing oxidizes the contacts and builds up silicon dioxide, opening the circuit. The result is brake lights that do not illuminate (a rear-end-collision hazard) and, because the same switch signals the shift interlock, an inability to shift the transmission out of Park. Nissan recalled 807,376 Sentras under campaign PM971 (NHTSA 21V-135).
Common Symptoms
- Brake lights do not illuminate when pedal is pressed
- Brake lights stuck on
- Cannot shift out of Park
- Cruise control inoperative
- Intermittent push-button start issues
How to Fix
Have the dealer perform recall PM971 / 21V-135: replace the stop lamp switch and install a protective grommet at no cost. Outside the recall, the switch is an inexpensive part; confirm by checking whether brake lights work and whether the brake-pedal-press releases the shift interlock before condemning the shifter assembly.
Sources for this issue (3)
P0504 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0504 mean on a Nissan?
P0504 stands for "Brake Switch "A"/"B" Correlation." Most vehicles use two independent brake switch signals (a normally-open and a normally-closed circuit, switch A and switch B). The PCM compares them and expects them to change state together when the brake pedal is pressed. P0504 sets when the two signals disagree (do not correlate), indicating one switch or circuit is faulty. On Nissan it is documented across 1 model: Sentra.
What are the most common causes of P0504?
The most common causes of P0504 are: Failed brake light switch, Misadjusted brake switch (plunger gap), Wiring/connector fault on one of the two brake switch circuits, Blown brake-circuit fuse affecting one signal, Faulty PCM input. The specific cause varies by vehicle.
How much does it cost to fix P0504 on a Nissan?
Repair costs vary widely with the root cause and Nissan model; each issue on this page carries its own estimate where one is published.
Looking for P0504 on a different make?
View P0504 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.