BMW 335d engine malfunction related to filter issue and O2 sensor repair needed on BMW 335d

Some BMW 335d owners report experiencing engine malfunctions related to filter issues and O2 sensor repairs. These issues may manifest as noticeable loss of performance or engine hesitation, particularly when a defective upstream oxygen sensor is present, especially after 100,000 miles. Additionally, error codes related to the particulate filter system can indicate ongoing problems, even if warnings do not reappear after a full code clear. Insufficient Diesel Exhaust Fluid (DEF) levels can also trigger warnings and negatively affect engine performance, suggesting that simply refilling the DEF tank may resolve some issues. Furthermore, some owners have encountered constant vacuum or boost leaks, which can lead to a significant loss of boost at low revs, often undetected by service diagnostics. Lastly, receiving "Engine Malfunction" warnings indicates that the vehicle's performance has been intentionally limited due to detected system failures. Prompt attention to these concerns through proper diagnostics and repairs is crucial for maintaining optimal engine performance in the BMW 335d.