OBD2 Car ScannerWhat does C0040 mean?
C0040 stands for Brake Pedal Switch "A" (Subfault). A chassis module has found a fault in a system like ABS, traction or stability control, steering or suspension.
Chassis codes cover the ABS, traction control, steering and suspension. When the car's computer sees a reading outside its normal range, it stores this code and may turn on a warning light on the dashboard.
Common causes
- Faulty or dirty wheel speed sensor
- Damaged sensor wiring
- Low brake fluid
- Faulty ABS pump or module
What to do
- Read all stored and pending codes with a scanner. Several codes together often point to one cause.
- Note the freeze frame data (speed, temperature, load) recorded when the code was set.
- Inspect the wiring and connectors of the part named in the code for damage, corrosion or looseness.
- Fix the most likely and cheapest cause first, then clear the code and drive to see if it comes back.
Read this code from your own car
Plug in a cheap ELM327 adapter and the app shows every fault code, what it means and how to fix it.
Frequently asked questions
What does C0040 mean?
C0040 means “Brake Pedal Switch "A" (Subfault)”. It belongs to the chassis system group: A chassis module has found a fault in a system like ABS, traction or stability control, steering or suspension.
Is it safe to drive with C0040?
Avoid driving long distances. This kind of fault can cause damage or affect safety, so get it checked as soon as possible.
How do I clear C0040?
Fix the cause, then clear the code with an OBD2 scanner or app. If the fault is still there, the code will come back.
Related codes
- C003BRight Rear Wheel Speed Sensor Supply (Subfault)
- C003CRear Tone Wheel (Subfault)
- C003DRear Wheel Speed Sensor (Subfault)
- C003ERear Wheel Speed Sensor Supply (Subfault)
- C0041Brake Pedal Switch "B" (Subfault)
- C0042Brake Pedal Position Sensor "Circuit A" (Subfault)
- C0043Brake Pedal Position Sensor "Circuit B" (Subfault)
- C0044Brake Pressure Sensor "A" (Subfault)
Code meanings can vary by manufacturer. This page is general guidance, not a repair manual. Always confirm the cause before replacing parts.