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10 Most Common Check Engine Light Repairs

To avoid costly repairs down the road, be sure to take your vehicle to the nearest Mufflerman when your check engine light appears.


When the check-engine light appears, it’s easy to try and ignore it.

For many drivers, the dreaded check-engine light symbolizes hundreds of dollars on car repairs, as well as the added inconvenience of waiting for a mechanic to repair the vehicle promptly. It also produces a sense of anxiety within drivers, as the light appears with no warning or explanation. Rather, drivers are left to anxiously wonder what type of issue the light could be signaling.

While that orange, engine-shaped icon is often easy to ignore, failing to make an appointment with a qualified licensed technician and postponing repairs is proven to be a costly and damaging mistake.

Although the vehicle may appear to be problem-free, it’s always smarter to take the vehicle into The Mufflerman and have a qualified mechanic properly investigate the issue before it becomes a more costly repair.

This year, the Car Car Council of Canada released the top 10 check-engine light repairs from the annual CarMD Vehicle Health Index.

1. Faulty O2 Sensors

The most likely cause of the check-engine light is a faulty oxygen sensor, which is used to determine the amount of oxygen present in the vehicle’s exhaust. While it may cost the motorist a few hundred dollars to repair, ignoring the issue often results in more extensive damages. For example, faulty O2 sensors often lead to a 40% reduction in the car’s overall fuel economy.

2. Faulty Ignition Coils and Spark Plugs

This repair was also tied as the most common repair in 2018.  Luckily, changing spark plugs can sometimes be a low-cost maintenance item if the vehicle is serviced promptly. However, ignoring the check-engine sign will likely result in the ignition coil failing. This repair could cost hundreds of dollars.

3. Faulty Catalytic Converter Efficiency

This is the third most common repair — and also one of the most costly. The average cost to repair this in 2018 was $1,371. Most often, a catalytic converter won’t fail unless a root cause, such as a faulty spark plug, is ignored for too long.

4. Inspect Fuel Cap

Fuel cap related issues accounted for 4.18% of repairs in 2018. The average cost to replace a faulty gas gap is $26. However, ignoring the issue can result in reduced fuel economy, as well as environmental harm.

5. Faulty Ignition Coil

The Ignition Coil is responsible for helping to start the vehicle and keep it running. These coils often malfunction due to high temperatures under the hood, and can result in other problems — such as a pricey catalytic converter replacement — if left unfixed.

6. Faulty Evaporative Emissions Purge Control Valve

Down one spot this year, this is the sixth most common check-engine light repair in 2018. The valve is part of the car’s EVAP system and is a fairly simple fix. However, leaving it unchecked can result in further, more costly fixes.

7. Faulty Mass Airflow Sensor

The MAF determines how much fuel to inject into the engine. Failing to see a technician can lower the vehicle’s fuel economy quite substantially. 

8. Faulty Evaporative Emissions Purge Solenoid

This feature helps to control how much fuel vapor escapes into the atmosphere from your vehicle. The average cost to replace an Evaporative Emissions Purge Solenoid in 2018 was $155.

9. Faulty Fuel Injectors

Fuel Injectors help to ensure that the car’s fuel is released as a fine mist. A failing injector can result in a breadth of subsequent issues, such as engine misfires.

10. Faulty Thermostat

The tenth most common repair in 2019 was thermostat repairs. The thermostat helps to regulate the engine’s temperature. Thermostats can fail if the coolant is not changed when recommended, or if the vehicle is subjected to extreme conditions and temperatures.

Although it may seem easier to ignore the check-engine light and hope that the problem goes away, this is a costly mistake long-term. When the check-engine light appears, it’s best to address the issue and bring the vehicle into The Mufflerman before it becomes a larger, more expensive repair down the road.


Winter Tires can be the difference between making it out of your neighbourhood and working from home.

Winter is here, which means that the snow is beginning to come down, the roads are becoming icy, and driving is starting to become increasingly difficult.

To avoid unnecessary repairs, keep your car on the road, with your safety of utmost importance, follow these winter maintenance tips during the winter months.

Whether you're a homebody, or a pro road-tripper that travels across the country, we will have you road trip ready after reading this article.