C0040: owner reports and bulletins

Chassis. We haven't written the explanation for this code yet. Below is what owners and manufacturers have filed with NHTSA.

Got C0040 on your scanner? Tell the mechanic your year, make, model and any symptoms and you'll get the likely cause and what to check first. Ask about this code.

What owners report to NHTSA

11 complaints filed with NHTSA mention C0040, 5 of them since 2015, across 8 different models. The component owners most often filed it under: service brakes, hydraulic.

Most-reported models

VehicleComplaintsModel years reported
CHEVROLET COLORADO32004, 2005

Manufacturer service bulletins that name C0040

29 technical service bulletins and manufacturer communications filed with NHTSA mention C0040, from 6 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:

  • MAZDA CX-90 (2024), bulletin 10244568: Some customers may experience a "Push Button Start Malfunction. Have the Vehicle Inspected" warning message and the following DTC(s) may be stored. C0040:24 - Brake switch (No.1 signal) circuit malfunction P0504:00 - Bra…
  • FORD F-450 SD (2020, 2021, 2022), bulletin 10208141: Some 2020-2022 F-Super Duty vehicles may exhibit a condition where the engine will not turn off and/or have various electrical symptoms including a dead battery, horn stays on and no crank/no start. The vehicle may also …
  • FORD F-250 SD (2020, 2021, 2022), bulletin 10214495: Some 2020-2022 F-Super Duty vehicles may exhibit a condition where the vehicle will not shift out of park (P). Diagnostic trouble codes (DTC) C0040 and/or P0504 may also be present. Reference TSB 22-2044 to make sure tha…
  • FORD ESCAPE (2020, 2021), bulletin 10202798: Some 2020-2021 Escape vehicles may exhibit various symptoms due to a loss of voltage reference (VREF) from the 14290 harness above the steering shaft u-joint. Possible symptoms may include an illuminated malfunction indi…
  • CHEVROLET IMPALA (2019, 2020), bulletin 10170501: This engineering information (EI) revision ends the need for information from the field on a condition of wheel speed sensor inoperative with DTCs C0035, C0040, C0045 and/or C0055.
  • CHEVROLET COLORADO (2015, 2016), bulletin 10176322: This Preliminary Information communication provides information to the technician that vehicles may have an Antilock Braking System or Malfunction Indicator Lamp illuminated. Also Low Brake Fluid lamp on with the master …

Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.