2018 Toyota Mirai Has A Check Engine Light

Troubleshooting the Check Engine Light in Your 2018 Toyota Mirai: Common Causes and Solutions

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Reviewed by
Aisha
Written by RepairPal Car Genius
Updated January 14, 2025
0%
40% chance it's the
Emissions System
0%
60% chance it's
Something else
The most common reasons a 2018 Toyota Mirai has a check engine light are an emissions system component, a sensor, or a catalytic converter.
  • Emissions System: A faulty emissions system component, such as an oxygen sensor or EGR valve, can lead to increased emissions and trigger the check engine light.
Proper diagnosis will determine the exact cause of your symptom, saving you money on unnecessary repairs. The diagnostic experts at RepairPal Certified shops have the right tools and experience to solve any symptom.

How much does it cost to fix a 2018 Toyota Mirai has a check engine light?

Common Repairs

The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.

Like we noted in the last section, general diagnosis symptoms are the most vague of the bunch. There are several diagnostic spectrums, electrical diagnosis, drivability diagnostics, engine diagnostics, transmission diagnostics, and the list could continue for about 5 or 10 more spectrums of diagnostics. The most important take-away here, is that general diagnostics are diagnostics that have no other spectrum in which they fit, or the problem is unknown. This means that any vehicle left outside of a repair facility with the keys and an authorization to perform diagnosis will be diagnosed under the general diagnosis spectrum.

When the Check Engine Light comes on, you may experience engine performance issues such as poor acceleration, rough idling, or an engine that won't start. In some cases, no abnormal symptoms will be experienced. Other systems like the transmission or ABS can cause the Check Engine Light to illuminate and lights for those systems can come on at the same time. Similar lights may say "Check Engine Soon", "Malfunction Indicator Light" or just "Check". In rare case the engine can overheat.

What are the initial diagnostic steps to take for a check engine light on a 2018 Toyota Mirai?

When faced with a check engine light on your 2018 Toyota Mirai, it's essential to start with a systematic diagnostic approach. Begin by checking the gas cap; a loose or damaged cap is a common culprit that can easily trigger the light. Next, take a moment to inspect your dashboard for any additional warning indicators, as these can offer valuable insights into the underlying issue. A visual inspection under the hood is also crucial; look for any signs of damage to wires, hoses, or connectors that could be affecting your vehicle's performance. If these initial checks do not resolve the issue, using an OBD-II scanner can be a game-changer. This tool allows you to access error codes from your vehicle's computer, providing specific information that can guide your next steps. Finally, don’t forget to consult your owner’s manual, which can offer further context on what the check engine light signifies and suggest appropriate actions. By following these steps, you can effectively narrow down the potential causes of the check engine light and take informed action towards resolving the issue.

What are the common problems that could cause the check engine light to activate in a 2018 Toyota Mirai?

When the check engine light illuminates in your 2018 Toyota Mirai, it can be a source of concern, but understanding the common problems that may cause this warning can empower you to take action. One of the simplest issues to check is the gas cap; if it’s loose or damaged, it can disrupt the fuel system's pressure, triggering the light. Another frequent culprit is a faulty oxygen sensor, which not only affects fuel efficiency but also increases emissions. If you notice a decrease in performance, consider inspecting the catalytic converter, as problems here can also activate the light. Additionally, a malfunctioning mass airflow sensor can lead to an improper air-fuel mixture, impacting overall vehicle performance. Worn-out spark plugs or ignition coils can cause engine misfires, which are often indicated by the check engine light. Lastly, be aware of potential engine vacuum leaks or issues with the EGR valve, as these can also affect engine performance and emissions. By addressing these common issues promptly, you can help ensure your Mirai runs efficiently and avoid more significant repairs down the line.

What immediate actions should be taken when the check engine light appears in a 2018 Toyota Mirai?

When the check engine light illuminates in your 2018 Toyota Mirai, it’s crucial to act swiftly to avoid serious repercussions. Ignoring this warning can lead to significant engine damage or safety hazards on the road. Start by checking for any additional warning lights on the dashboard, as they may indicate a more severe issue that requires immediate attention. A simple yet often overlooked step is to ensure that the gas cap is securely tightened; a loose cap can easily trigger the check engine light. While driving, reduce your speed and avoid heavy loads to minimize stress on the engine until the problem is diagnosed. It’s also wise to inspect essential fluid levels, including engine oil and coolant, to ensure they are adequate. If the light persists, scheduling a diagnostic test with a certified mechanic is essential to pinpoint the exact issue. Addressing these concerns promptly not only safeguards your vehicle’s performance but also enhances your safety on the road.

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