C0420high severityChassis
Pre-Collision System Malfunction
on 2016 Audi A8 3.0L Supercharged V6 · AWD
What this code means
General fault in the pre-collision system that prepares or initiates emergency braking.
Symptoms
- Pre-collision system warning light
- Automatic emergency braking disabled
- Forward collision alert unavailable
- Driver assist systems degraded
Common causes
- Radar or camera sensor fault
- Control module failure
- Brake system fault preventing intervention
- CAN communication error between modules
Diagnostic steps
- Check for radar and camera codes first
- Verify brake system is fully operational
- Test CAN communication between PCS modules
- Check all sensor alignments
- Inspect wiring to PCS components
Repair notes
Diagnose root sensor or communication fault. PCS depends on multiple subsystems.
Other Chassis codes on this vehicle
C0021
LF Wheel Speed Sensor Range/Performance
C0022
RF Wheel Speed Sensor Range/Performance
C0023
LR Wheel Speed Sensor Range/Performance
C0024
RR Wheel Speed Sensor Range/Performance
C0025
LF Wheel Speed Sensor Circuit Intermittent
C0026
RF Wheel Speed Sensor Circuit Intermittent
C0027
LR Wheel Speed Sensor Circuit Intermittent
C0028
RR Wheel Speed Sensor Circuit Intermittent
C0035
Left Front Wheel Speed Sensor Circuit
C0036
Left Front Wheel Speed Signal Erratic