Which of the following could cause a vehicle's check engine light to activate?

The reason the check engine light may activate is due to a variety of issues related to the vehicle's performance or emissions system. This warning light is part of the vehicle's onboard diagnostics and serves to alert the driver that there is a potential problem that requires attention. It can be triggered by issues ranging from minor malfunctions, such as a loose gas cap, to more significant problems, such as engine misfires or catalytic converter failures.

While a dead battery, low tire pressure, and an empty fuel tank can affect vehicle operation, they do not typically activate the check engine light. Instead, these issues would often trigger other specific warnings or alerts on the dashboard. For instance, a dead battery may prevent the engine from starting at all, and low tire pressure is usually indicated by a separate tire pressure monitoring system (TPMS) light. An empty fuel tank might result in an out-of-fuel situation, but it is generally indicated by a fuel gauge warning.

Thus, the check engine light serves as a broader signal encompassing a range of possible concerns, which is why recognizing that it could activate due to a variety of issues is crucial for proper vehicle maintenance and diagnosis.