Cadillac Catera check engine light remains on due to DTC P411, failing emissions test on Cadillac Catera

Some Cadillac Catera owners report experiencing persistent check engine light issues due to DTC P411, which can lead to failures in emissions tests. These problems may stem from a variety of causes, such as a loose or faulty gas cap, which can sometimes be resolved by simply re-tightening it. Additionally, owners may encounter issues related to aftermarket alarms, faulty ignition coils, or engine misfires, which can manifest as abnormal engine behavior like loud pops or shaking. Utilizing an OBD scanner is recommended for reading and clearing the check engine light, while a full system scanner designed for Cadillac models can help pinpoint the root cause more effectively. Ensuring the gas cap is secure is crucial, as a loose or broken cap can lead to fuel pressure issues and increased emissions. Addressing these concerns promptly is important for maintaining proper engine performance and successfully passing emissions tests.