Volkswagen Passat DEF light on despite adequate fluid level, vehicle won't start after shutdown on Volkswagen Passat

Some Volkswagen Passat owners report experiencing issues with the DEF light remaining on despite having an adequate fluid level, which can lead to the vehicle not starting after shutdown. These problems may occur if the car is not parked on level ground when adding DEF, or if the ignition is not switched on for at least 30 seconds after refilling the DEF tank to allow the system to detect the refill. Additionally, some owners find that manually resetting the warning through the dash display may not always be effective. In certain cases, disconnecting the negative battery cable to perform a system reset can help, but if the warning light continues to reappear, it may indicate a more significant issue that could affect the DPF regeneration process and trigger a check engine light. Prompt attention to these concerns is advised to ensure the vehicle operates correctly.