Fault code C1221 – a step-by-step guide to diagnosing and fixing it

Error code C1221 is displayed and the check engine light is on - what does this mean?

The DTC C1221 is recognized by the OBD/EOBD system when there is a problem with the ABS wheel speed sensor on the right front wheel. This error code indicates that the anti-lock braking system is receiving an implausible or missing signal value from the corresponding sensor. The exact designation may vary for different manufacturers, but always refers to the wheel speed detection of the ABS system.

What causes can this error code have?

• Defective ABS wheel speed sensor on the right front wheel
• Damaged or broken sensor cable
• Corroded or loose plug connections
• Dirty or damaged sensor ring (reluctor ring)
• Defective ABS control unit
• Interruption in the wiring to the sensor
• Mechanical damage to the sensor holder
• Excessive air gap between sensor and sensor ring

Which symptoms occur in parallel with fault code C1221?

• ABS warning light: Permanent activation of the ABS indicator light in the dashboard
• ESP malfunction: Failure or limited function of the electronic stability program
• Brake assist problems: Reduced effectiveness of brake assist systems
• Uneven braking behavior: Locking wheels during heavy braking maneuvers
• Traction control: Malfunction of the traction control system
• Diagnostic messages: Additional error codes in connection with the ABS system

How can the problem with fault code C1221 be rectified?

• Correcting trouble code C1221 requires a systematic diagnosis of the ABS components on the right front wheel.
• Sensor check and replacement: Check the ABS wheel speed sensor on the right front wheel for damage, measure resistance values and replace with an original part if defective
• Cable diagnostics: Check the entire wiring from the sensor to the ABS control unit for breaks, short circuits or corrosion and repair or replace damaged sections
• Clean plug connections: Clean all electrical connections of the sensor, use contact spray and ensure tight fit of the connectors
• Sensor ring maintenance: Check the reluctor ring on the wheel bearing for dirt, damage or missing teeth and replace if necessary
• Adjust the air gap: Adjust the correct distance between the sensor and sensor ring (usually 0.5-2.0 mm) and replace the sensor bracket if necessary
• Control unit reset: After the repair, delete the fault memory, carry out a test drive and have the ABS system recalibrated