What can trigger the check engine light in vehicles, indicating a potential emissions issue?

The check engine light is designed to alert drivers to a range of potential issues within the vehicle, particularly those related to emissions control and engine performance. One of the most common triggers for the check engine light is faulty sensors or damaged exhaust systems.

Modern vehicles have various sensors, such as the oxygen sensor and mass airflow sensor, that monitor emissions and fuel efficiency. If one of these sensors malfunctions, it can lead the engine control unit to detect an imbalance in the air-fuel mixture or improper exhaust gases, which triggers the check engine light. Additionally, a damaged exhaust system may lead to increased emissions or failure to meet environmental regulations, prompting the warning.

In contrast, low tire pressure, while important for vehicle safety and fuel efficiency, does not directly relate to engine emissions, and therefore does not typically trigger the check engine light. An oil change required signal pertains to engine maintenance rather than emissions concerns, and a low fuel warning, while it indicates a need for refueling, does not correlate with emissions issues. Thus, the presence of faulty sensors or a damaged exhaust system is the most direct link to emissions-related problems, making it the correct answer.