Ford Fiesta Has A Check Engine Light

Troubleshooting Common Causes for the Check Engine Light in Your Ford Fiesta and How to Resolve Them

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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 Ford Fiesta 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 Ford Fiesta 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.

A faulty oxygen sensor is one of the most common causes of a check engine light. Symptoms may include a decrease in fuel mileage, hesitation or misfiring from the engine, rough idling or even stalling. A faulty sensor may cause the vehicle to fail an emissions test.

Any time there is an emissions fault the check engine light will be displayed. The purpose of the check engine light is to inform the driver that an emission related fault has been found, and that there are on-board diagnostic (OBD) trouble codes stored in the powertrain or engine control module. Additionally, since the emissions systems are so intertwined into engine control and transmission control systems, symptoms may include nearly any sort of drivability concerns. This may include harsh shifting, failure to shift, hesitation on acceleration, jerking, engine failure to start or run, loss of power, or any number of other drivability issues.

Due to the nature of electrical systems on modern vehicles, the range of problems these can cause are nearly limitless. However, there is a way to categorize them in two ways. Permanent and intermittent problems. Permanent problems appear and remain. This may be the vehicle will not start, the radio does not work, or the door chime will not turn off among many, many others. These problems are more straight-forward to diagnose since they present themselves at all time. This means there will always be a fault to find. Intermittent electrical problems, however, can be difficult or impossible to locate, since they appear then disappear without warning. The best case scenario for an intermittent issue is when replicating the problem is easily accomplished and understood. This allows a technician to make an issue semi-permanent, allowing them to find the fault. Other issues that come and go without warning and cannot be replicated on demand must occur when the technician is servicing the vehicle, otherwise there is no problem to correct. It is most important to understand that electrical system faults always require inspection, and can include the vehicle working in any manner, or not working at all.

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.

Troubleshooting Check Engine Light in a Ford Fiesta

When faced with a check engine light in your Ford Fiesta, adopting a diagnostic approach is essential for effective troubleshooting. Start by gathering an OBD-II scanner to pull the trouble codes, as these codes provide critical insights into the specific issues affecting your vehicle. Once you have the codes, take the time to research their meanings and prioritize addressing the simplest problems first, such as checking for loose gas caps or faulty sensors. After making the necessary repairs, it’s important to drive your Fiesta for a short distance to allow the vehicle’s computer to reset and confirm that the issue has been resolved. Remember, common culprits like ignition cylinder issues or oxygen sensor malfunctions can often trigger the check engine light, so keep these in mind as you diagnose. By systematically identifying and resolving the underlying problems, you can maintain your vehicle’s performance and prevent more serious issues from arising.

What Could Cause the Check Engine Light to Illuminate in a Ford Fiesta?

When the check engine light comes on in your Ford Fiesta, it can be a source of concern, but understanding the common problems can help you diagnose the issue effectively. One of the most frequent culprits is a loose or faulty gas cap, which can lead to fuel system leaks and disrupt the pressure balance, triggering the warning light. Additionally, ignition cylinder problems may cause irregular engine performance, indicating that it might be time to inspect this component. Another common issue is a malfunctioning exhaust gas oxygen sensor, which can result in misfires during acceleration or low-speed driving. Other potential causes include bad spark plugs or a faulty O2 sensor, both of which can affect engine efficiency and performance. Addressing these issues promptly is crucial for maintaining your vehicle's health. If you manage to identify and resolve the underlying problem, you can easily reset the check engine light by disconnecting the battery terminals for about 30 seconds, allowing you to get back on the road with peace of mind.

Why is the Check Engine Light On in a Ford Fiesta?

When the Check Engine Light illuminates in your Ford Fiesta, it is crucial to understand that this warning is not just a minor inconvenience; it signifies potential issues that could escalate into serious problems if left unaddressed. Common culprits such as a faulty oxygen sensor or emissions system components can lead to decreased fuel efficiency, engine misfires, and rough performance, which not only affect your driving experience but can also result in costly repairs down the line. Ignoring the light may lead to more severe engine damage or failure, which could compromise your vehicle's safety and reliability. Furthermore, if you plan to undergo emissions testing, a lit Check Engine Light can result in an automatic failure, preventing you from legally driving your vehicle. Therefore, it is essential to diagnose and resolve the underlying issues promptly to ensure your Ford Fiesta remains in optimal condition and to avoid the risk of significant damage or safety hazards.

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