C0021
LF Wheel Speed Sensor Range/Performance
2002-2005 Audi A4 3.0L V6
Moderate SeverityChassisGeneric (SAE)
Description
The left front wheel speed sensor output is outside the expected range under current driving conditions.
Symptoms
- ABS warning light on
- Traction control light on
- Speedometer fluctuation
- ABS activating at inappropriate times
Common Causes
- Wheel speed sensor air gap too large
- Tone ring corrosion or damage
- Sensor magnet weakened
- Wheel bearing excessive play
Diagnostic Steps
- Compare all four wheel speed sensor readings at steady speed
- Inspect sensor air gap with feeler gauge
- Check tone ring for missing teeth or rust
- Inspect wheel bearing for play
- Scope sensor output waveform
Repair Notes
Adjust sensor air gap or replace sensor. Inspect tone ring for damage.
Related Codes
Other Chassis Codes
- C0022RF Wheel Speed Sensor Range/Performance
- C0023LR Wheel Speed Sensor Range/Performance
- C0024RR Wheel Speed Sensor Range/Performance
- C0025LF Wheel Speed Sensor Circuit Intermittent
- C0026RF Wheel Speed Sensor Circuit Intermittent
- C0027LR Wheel Speed Sensor Circuit Intermittent
- C0028RR Wheel Speed Sensor Circuit Intermittent
- C0035Left Front Wheel Speed Sensor Circuit
- C0036Left Front Wheel Speed Signal Erratic
- C0040Right Front Wheel Speed Sensor Circuit
C0021 on Other Vehicles
Common Questions
What does code C0021 mean on a 2002-2005 Audi A4?
C0021 stands for "LF Wheel Speed Sensor Range/Performance". The left front wheel speed sensor output is outside the expected range under current driving conditions.
What are the symptoms of C0021 on a Audi A4?
Common symptoms of C0021 include: ABS warning light on, Traction control light on, Speedometer fluctuation, ABS activating at inappropriate times.
What causes C0021 on a 2002-2005 Audi A4?
Common causes of C0021 include: Wheel speed sensor air gap too large, Tone ring corrosion or damage, Sensor magnet weakened, Wheel bearing excessive play.