Frequently Asked Questions

What is the most common reason for check engine light on a 2021 Lexus IS 300?

• Loose or faulty gas cap: a simple fix that often clears the code and restores fuel system pressure.
• Oxygen sensor degradation: affects fuel trim and emissions; delaying repair increases fuel use and catalytic wear.
• EVAP system leaks: small leaks can trigger codes and fail emissions tests if left unresolved.
• Ignition misfires or worn spark plugs: can cause rough idle, poor acceleration, and potential catalytic damage.
• Our certified technicians diagnose the root cause and explain immediate and long-term savings from proper, dealer-performed repairs.

What does it mean when the check engine light comes on in a 2021 Lexus IS 300?

• It indicates the vehicle’s onboard diagnostic system detected an issue that affects emissions, engine performance, or drivability.
• Codes range from minor (loose cap, sensor) to serious (misfire, catalytic failure); a scan reveals the specific code and probable causes.
• A steady light usually means non-emergency repair is needed; a flashing light indicates a more severe problem requiring immediate attention.
• Diagnostics at our dealership identify underlying faults and help avoid costly downstream repairs; warranty-covered repairs must be performed at a certified dealership.

What is the first thing to check when the check engine light comes on?

• Confirm the gas cap is tight and undamaged; it’s an easy first step and often resolves the code.
• Check basic fluids and look for obvious issues like disconnected hoses or low oil that could trigger sensors.
• If the light persists, schedule a diagnostic with us—our factory-trained techs use Lexus-specific tools for accurate diagnosis.
• Any repair covered under warranty must be completed at a certified dealership to preserve coverage and ensure genuine parts and proper calibration.

How long does a check engine light service take?

• Basic diagnostic scans typically take 30–60 minutes to read codes, capture freeze-frame data, and perform initial checks.
• Simple repairs, like replacing a gas cap or oxygen sensor, may be completed the same day; more involved repairs require additional time for parts and testing.
• We provide clear time estimates when you arrive and prioritize efficient repairs while ensuring thorough testing to prevent repeat visits.
• Choosing our dealership yields immediate and long-term savings through accurate diagnosis, factory parts, and technicians trained to maintain Lexus performance and warranty integrity.

How much does a check engine light diagnostic cost for a 2021 Lexus IS 300?

• Typical diagnostic fees range from approximately $90–$150, depending on the depth of testing required; fees may be applied toward necessary repairs.
• Nalley Lexus Smyrna often costs less than independent shops when factoring in accurate diagnosis, OEM parts, and fewer follow-up visits—delivering immediate and long-term savings.
• We run targeted tests to avoid unnecessary parts replacement and provide transparent estimates before any work begins.
• Remember: any repairs covered under warranty must be performed at a certified dealership to keep coverage valid and ensure proper repair procedures.