P0504 Fault Code

Brake Switch A / B Correlation

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0504 fault code indicates a correlation problem between Brake Switch A and Brake Switch B. This fault typically occurs when the Engine Control Module (ECM) detects a disagreement between the two brake switch inputs. This could lead to improper functioning of various systems in the vehicle that depend on accurate brake signal inputs, such as cruise control and anti-lock braking systems.

What are the symptoms of the P0504 code?

Drivers may experience several symptoms related to the P0504 code:

• Brake lights that either do not illuminate or are stuck on
• Inoperable cruise control
• Warning lights on the dashboard, such as the ABS or brake warning light
• Unresponsive braking systems in specific situations.

What causes the P0504 code?

Common causes of the P0504 code include:

• Faulty brake light switch
• Wiring issues or short circuits in the brake switch circuit
• Corroded or loose connectors
• Malfunctioning ECM
• Misalignment of the brake switch, which can prevent it from functioning correctly.

How to fix P0504?

To resolve the P0504 fault code, consider the following steps:

1. Inspect the brake light switch and ensure it is functioning correctly; replace if necessary.
2. Examine the wiring and connectors associated with the brake switch for signs of damage or corrosion.
3. Test the brake switch inputs using a multimeter to check for proper voltage readings.
4. If all else fails, consider reprogramming or replacing the ECM, especially if other faults are present.