What does it mean?
C1440 is a Chassis (ABS, traction control, steering) fault code. It indicates: Pressure Transducer Main/Primary Signal Faulted .
Symptoms
- ABS, stability and brake warning lamps on, often with a brake system message
- Firmer pedal or loss of hydraulic boost on systems with electro-hydraulic assist
- Longer stopping distance and no ABS support during hard braking
- Hydraulic pump runs more often or for longer than normal
- Pedal feel changes from one stop to the next
Likely causes
- Failed transducer element that has drifted out of range or reads a fixed value
- Open circuit, short to ground or short to battery in the signal wire
- Missing reference voltage or a poor ground at the transducer
- Moisture and corrosion in the connector at the hydraulic unit or master cylinder
- Air in the hydraulic circuit or low fluid, so measured pressure never matches the commanded value
- Contaminated or old brake fluid damaging the sensor element
- Failed input circuit inside the brake control unit
How to fix it
- Read the transducer live value with the pedal released; it should sit near zero and rise smoothly as the pedal is pressed
- Check brake fluid level and condition, and bleed the system if air is suspected
- Backprobe reference voltage and ground at the transducer with the ignition on
- Test the signal wire for open, short to ground and short to battery back to the module
- Compare the primary reading with the redundant or secondary sensor where one is fitted
- Clean, dry and reseal the connector, and check for a water trap in the harness above it
- Replace the transducer, or the hydraulic unit where the sensor is not serviced separately, then bleed and road test