B0421moderate severityBody
ABS Warning Lamp Circuit
on 2003 Audi S6 4.2L V8 · FWD
What this code means
Malfunction in the ABS warning lamp circuit. The lamp may not illuminate or may stay on incorrectly.
Symptoms
- ABS light does not come on during bulb check
- ABS light always on
- Cannot determine ABS system status
- Light flickering
Common causes
- Burnt out lamp
- Cluster fault
- ABS module lamp driver failure
- Wiring issue
Diagnostic steps
- Check lamp during key-on bulb check
- Scan ABS module for codes
- Test lamp drive circuit
- Inspect wiring from ABS module to cluster
Repair notes
Replace ABS warning lamp or repair wiring circuit.
Other Body codes on this vehicle
B0001
Driver Frontal Stage 1 Deployment Control
B0002
Driver Frontal Stage 2 Deployment Control
B0003
Passenger Frontal Stage 1 Deployment Control
B0004
Passenger Frontal Stage 2 Deployment Control
B0005
Driver Knee Airbag Deployment Circuit
B0006
Passenger Knee Airbag Deployment Circuit
B0010
Driver Side Airbag Deployment
B0011
Driver Side Airbag Deployment Circuit Open
B0012
Driver Side Airbag Deployment Circuit Short to Ground
B0013
Driver Side Airbag Deployment Circuit Short to Battery