C1940 — Brake Pressure Switch Mechanical Failure #

Note: The description of code C1940 may vary depending on the vehicle manufacturer. Always refer to your vehicle’s official service documentation for the exact terminology.

• Brake Pressure Switch Mechanical Failure (Generic/OEMs)
• Brake Pressure Sensor Mechanical Failure (Ford, Lincoln, Mazda)
• Brake Pressure Switch Fault (Toyota, Lexus)
• Brake Pedal Pressure Switch Malfunction (Nissan, Infiniti)

Summary of Code C1940 #

The C1940 code signals a mechanical failure in the brake pressure switch—a component that detects hydraulic pressure in your vehicle’s brake system. This switch communicates with the ABS (Anti-lock Braking System) control module to confirm that the expected brake pressure is present during braking events. When a mechanical issue is detected, the system may disable some advanced braking features and illuminate warning lights on your dashboard. While the code itself doesn’t pinpoint the exact nature of the failure, it does indicate that the switch isn’t physically responding as it should. Prompt diagnosis and repair are recommended to maintain safe braking performance.

Common Symptoms for Code C1940 #

A brake pressure switch mechanical failure typically triggers warning lights and may affect how your vehicle’s advanced safety systems function. You may notice the following:

• ABS warning light illuminated
• Brake warning light illuminated
• Loss of ABS or traction control functionality
• Unresponsive or erratic brake pedal feel
• Longer stopping distances in emergency braking
• Occasional chime or message on the instrument cluster

Probable Causes for Code C1940 #

Code C1940 can result from several underlying issues, most commonly centered on the brake pressure switch’s mechanical integrity. Here are the most frequent causes, listed in order of likelihood:

1. Sticking or jammed brake pressure switch (internal wear or contamination)
2. Mechanical damage to the switch (cracks, broken housing)
3. Hydraulic fluid contamination leading to restricted or blocked switch movement
4. Incorrect installation or adjustment of the switch
5. Wear or aging of the switch’s internal components (springs, contacts)
6. Faulty or damaged connecting linkage between pedal and switch (less common)

Step-by-Step Diagnosis for Code C1940 #

Diagnosing a mechanical brake pressure switch failure requires a methodical approach to rule out electrical and hydraulic issues and confirm a physical or mechanical problem with the switch. Here’s how a professional technician would proceed:

• 1. Confirm the code using a professional-grade OBD-II/EOBD scan tool; note any related brake or ABS codes.
• 2. Inspect brake fluid level and condition; check for contamination that could affect switch operation.
• 3. Locate and visually inspect the brake pressure switch for physical damage, leaks, or loose connections.
• 4. Disconnect the switch and check for mechanical sticking by manually operating the switch (if possible).
• 5. Test switch operation with a multimeter (checking for continuity as the brake pedal is pressed and released).
• 6. Verify correct installation and adjustment per OEM specifications.
• 7. If no issues are found, inspect the hydraulic lines for blockages or internal contamination that could affect switch function.
• 8. Clear the code and perform a test drive to see if the code returns after repairs or adjustments.