What Does C1940 Mean?
The ABS/stability control module has determined that the brake pressure switch is electrically functional but mechanically stuck or not operating correctly — it is not changing state when expected during normal driving. This means the module sees a valid signal but the switch does not transition between on and off appropriately during braking events. The driver may notice ABS/traction control warnings and degraded brake-assist performance.
Common Causes
35%
Brake pressure switch plunger is sticking or mechanically seized
30%
Brake pedal bumper pad (stop lamp switch contact pad) deteriorated or missing
20%
Brake switch mounting bracket bent or misaligned, preventing proper plunger travel
10%
Brake pedal pivot binding or excessive friction preventing full return travel
5%
Internally degraded switch with inconsistent contact behavior
Diagnostic Steps
1
Visually inspect the brake pedal assembly — check that the rubber bumper pad that contacts the brake switch plunger is present and intact. A missing bumper pad is one of the most common causes of this code.
2
With the engine off, press and release the brake pedal while listening and feeling for the brake switch clicking. It should produce a distinct click in both directions. A mushy or absent click indicates mechanical failure.
3
Monitor the brake switch PID in live data while slowly pressing and releasing the brake pedal multiple times. The transition point should be consistent. Erratic or delayed transitions confirm a mechanical issue.
4
Check the brake switch mounting — it should be firmly seated in its bracket with no play. The plunger should have approximately 1-3mm of free play before contacting the pedal arm.
5
If the bumper pad is missing, install the OEM replacement (typically a small rubber or plastic stopper). Clear codes and test drive to verify the fix.
Estimated Repair Cost
$5 - $150
Parts + labor, varies by vehicle and location
The ABS/stability control module has determined that the brake pressure switch is electrically functional but mechanically stuck or not operating correctly — it is not changing state when expected during normal driving. This means the module sees a valid signal but the switch does not transition bet...
The most common cause of C1940 (Brake Pressure Switch Mechanical Failure) is: Brake pressure switch plunger is sticking or mechanically seized
Typical repair costs for C1940 range from $5 to $150, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Basic braking is not impaired, but ABS functionality, brake-assist, and stability control may be degraded or disabled. Brake lights may stay on or not illuminate correctly, affecting other drivers' awareness. Repair soon to restore full safety system operation.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1940 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Chassis
System
ABS / Brake System
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
