Frequently Asked Questions

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

• Confirm the fuel cap is fully tightened—this common issue can trigger an emissions fault and is an easy fix.
• Note any symptoms: loss of power, unusual noises, or a flashing light—these change the urgency.
• A simple code scan identifies the system or sensor at fault; avoid resetting the light without diagnosis.
• If the light is flashing, stop driving and have the vehicle inspected to avoid further damage to the engine or catalytic converter.
• For warranty-covered repairs, remember they must be completed at a certified dealership like Nalley Toyota of Roswell.

What does it mean when the check engine light comes on in a 2004 Toyota Sienna?

• It signals an emissions, sensor, or engine management issue—codes range from loose gas cap to misfires or oxygen sensor faults.
• Some causes are minor and non-urgent; others require immediate attention to prevent damage or safety risks.
• A diagnostic scan pinpoints the trouble code so our technicians can recommend the appropriate repair or part replacement.
• Using our dealership ensures genuine Toyota parts, Toyota-trained technicians, and documentation required for warranty coverage.
• Bringing your Sienna to Nalley Toyota of Roswell often delivers immediate and long-term savings compared with independent shops while maintaining higher service standards.

What is the most common reason for check engine light on a 2004 Toyota Sienna?

• Common triggers include a loose or faulty gas cap, failing oxygen sensors, evaporative emissions leaks, and ignition misfires.
• Oxygen sensors and evap system faults are frequent on older vehicles and affect fuel economy and emissions compliance.
• Misfires risk catalytic converter damage—an expensive consequence if left unaddressed.
• Our technicians diagnose root causes rather than treating symptoms, helping you avoid repeat visits and extra costs.
• Repairs covered by warranty must be completed at a certified dealership to ensure coverage and proper parts installation.

How much does a check engine light diagnostic cost for a 2004 Toyota Sienna?

• Diagnostic fees typically range but Nalley Toyota of Roswell offers transparent pricing and may waive diagnostics with qualifying repairs—ask about current service specials.
• Simple fixes like tightening the gas cap or replacing a sensor are comparatively low cost; complex repairs such as catalytic converter replacement are more expensive.
• Common parts cost examples: O2 sensors and sensors $150–$400, MAF sensors $200–$500, catalytic converters $900–$2,000 depending on parts and labor.
• Using our dealership often costs less than independent shops when you factor immediate diagnostics, accurate repairs, genuine parts, and long-term reliability.
• Remember: warranty-covered repairs must be performed at a certified dealership to remain eligible for coverage.

How long does a check engine light service take?

• A diagnostic scan usually takes 30–90 minutes; simple repairs can often be completed the same day.
• Repair duration depends on the issue—sensor changes may be under two hours; complex engine or exhaust work can take longer.
• We provide clear time estimates after diagnosis and prioritize repairs to minimize downtime and cost to you.
• Because we use Toyota-trained technicians and factory parts, repairs are done right the first time, saving you time and reducing repeat visits.
• Warranty repairs must be carried out at a certified dealership, ensuring proper documentation and long-term protection for your vehicle.