Could check engine light is on be caused by loose or bad gas cap?

Surprisingly common. Tighten the cap until it clicks; the light may take a few drives to clear.

Could check engine light is on be caused by faulty oxygen sensor?

O2 sensors monitor exhaust composition. They wear out around 100,000 miles and trigger codes like P0131-P0167.

Misfire codes (P0300-P0308) are usually plugs, coils, or fuel injectors.

P0420/P0430 codes often point to catalytic converter efficiency. These are expensive to replace.

A dirty MAF sensor causes hesitation and codes like P0101.

Severity is rated Medium. Get the codes read at any auto parts store (free) or with an OBD2 scanner. Use our OBD2 lookup for code-specific guidance.

A solid check engine light is informational. A flashing light is urgent — pull over.

Severity: Medium

Get the codes read at any auto parts store (free) or with an OBD2 scanner. Use our OBD2 lookup for code-specific guidance.

Loose or bad gas cap: Surprisingly common. Tighten the cap until it clicks; the light may take a few drives to clear. Shop fuel cap
Faulty oxygen sensor: O2 sensors monitor exhaust composition. They wear out around 100,000 miles and trigger codes like P0131-P0167. Shop oxygen sensor
Misfiring spark plugs or coils: Misfire codes (P0300-P0308) are usually plugs, coils, or fuel injectors. Shop spark plugs
Failing catalytic converter: P0420/P0430 codes often point to catalytic converter efficiency. These are expensive to replace. Shop catalytic converter
Mass airflow sensor: A dirty MAF sensor causes hesitation and codes like P0101. Shop mass airflow sensor