Fault code C1140 – a step-by-step guide to diagnosing and fixing it

Error code C1140 is displayed and the check engine light is on - what does this mean?

The DTC C1140 is recognized by the OBD/EOBD system and indicates a problem with the rear right wheel speed sensor. This error code affects the ABS system and can impair the function of the anti-lock braking system and the electronic stability control. The exact designation may vary slightly for different manufacturers, but always refers to the rear right wheel speed sensor.

What causes can this error code have?

• Defective rear right wheel speed sensor
• Damaged or interrupted sensor cable
• Corroded or loose plug connections
• Dirty or damaged sensor ring on the wheel
• Defective ABS control unit
• Mechanical damage to the wheel bearing
• Incorrectly fitted sensor after repairs
• Electromagnetic interference from other components

What symptoms occur in parallel with fault code C1140?

• ABS warning light: The ABS indicator light in the dashboard lights up continuously
• ESP malfunction: The electronic stability program can be deactivated
• Braking behavior: The ABS may not function properly during emergency braking
• Traction control: The traction control may be impaired or deactivated
• Missing speed data: Irregular or missing speed measurements
• Vehicle diagnostics: Other error codes related to the ABS system may occur

How to fix the problem of trouble code C1140?

• Correcting trouble code C1140 requires a systematic diagnosis and targeted repair measures.
• Carry out sensor cleaning: Remove the rear right wheel speed sensor, clean thoroughly and check for damage, then refit correctly
• Cable check and repair: Check the entire sensor cable for breaks, chafing or corrosion and repair damaged areas or replace the cable completely
• Revise plug connections: Clean all sensor plug connections, use contact spray and check for tight fit, replace corroded plugs
• Check the sensor ring: Check the pulse ring on the wheel for dirt, damage or missing teeth and replace if defective
• Replace the sensor completely: If the wheel speed sensor is defective, install a new OEM sensor and calibrate it correctly
• Check ABS control unit: Test the ABS control unit using professional diagnostic technology and have it replaced or repaired if defective