Check Engine Light Repair Cost [Diagnostic & Repair]
When the check engine light in your car comes on, your first thoughts are probably: “How much will this cost me?’ For many, the check engine light is the last thing they want to see because it could be a sign of an expensive repair.
It can produce a lot of anxiety because the light may not tell you exactly what is wrong.
On average, you can expect to pay about $100 to diagnose a check engine light problem. The costs of repair depend on the nature of the engine error.
Some things, such as a loose gas cap or faulty wire, may cost less than $100 to fix, while more serious issues like a broken catalytic converter will cost $1,500 or higher.
You can buy a decent OBD scan tool to diagnose check engine light issues yourself for $80 on average.
The check engine light can trigger for a ton of reasons, some serious, others not so much. So we put together this guide on the average costs to fix a check engine light problem.
We will cover the costs of repairing the most common check engine light issues.
What Does the Check Engine Light Do?
The check engine light serves to notify you of any issues with your car’s engine or electrical systems. You can think of the check engine light as a way your car “talks” to you to let you know something is wrong.
The check engine light is controlled by the main control unit, which monitors the engine, transmission, and exhaust systems. When the control unit senses something wrong, it flips the check engine light to notify you about the problem.
The tricky thing about the control engine light is that it is not always obvious what the problem is. The light could indicate a small problem like a loose gas cap or it could indicate that your emissions system is failing.
How Much Does it Cost to Repair a Check Engine Light Issue?
The first thing you need to do is diagnose the problem. The check engine light could signify multiple problems so you need to figure out what is wrong in the first place.
It will cost about $100 on average to take your car to a mechanic and have them diagnose the check engine light problem. The typical price range for a diagnosis is between $70 to $120.
Faulty Oxygen Sensor
The most common check engine light problem is a broken oxygen sensor. The oxygen sensor detects the concentration of oxygen in the engine’s exhaust. When the oxygen air ratio is off, it sends a code to the engine to adjust the fuel injection.
When the sensor fails, the control module no longer receives data and it flips your check engine light.
Generally speaking, it costs about $60 on average to replace an oxygen sensor. The typical price range is between $20 on the low end and $100 on the high end.
Modern cars can have either one, two, three, or four oxygen sensors, depending on the make and model of your engine.
For example, the base model Honda Civic comes with two oxygen sensors, so you can expect to pay abou5t $120 to replace both. Experts recommend changing all oxygen sensors once every 65,000 miles and that you replace all of them at once.
Broken Spark Plug/Glow Plug
The spark plug provides the spark that ignites the fuel in the engine. Diesel engines have an analogous part called a glow plug that heats and starts the combustion reaction. If the spark plug is broken, the engine will not be able to start properly.
You can expect to pay about $250 on average to replace a spark plug. The parts cost about $100 while labor costs $150 on average. A broken glow plug in a diesel engine will cost you around $400 on average to replace.
Generally speaking, cars have one spark plug per engine cylinder. So for example, a 6-cylinder engine will usually have six separate spark plugs.
While not required, it is usually recommended to replace them all at once so they have consistent performance and wear. So for a V6 engine, you can expect to pay about $1,200 on average to replace all of the spark plugs. Alternatively, a V-4 diesel engine will cost about $2,000 to replace all of the glow plugs.
Faulty Catalytic Converter
The catalytic converter is an important part of your car’s emissions system that works to reduce the presence of nitric oxides in the exhaust.
Nitric oxides are a byproduct of the combustion reaction and are toxic for people and the environment. Catalytic converters use platinum components to convert nitric oxide into less harmful gasses.
Catalytic converters are one of the more expensive parts of your car’s emissions system. On average, you can expect to pay about $1,500 to replace a catalytic converter.
The typical price range is between $500 on the low end and $2,500 on the high end. Converters are expensive because they use rare materials (platinum, palladium, rhodium) for chemical reaction.
Most cars only have one catalytic converter, but a handful of models have two, three, or four. Generally speaking, one catalytic converter is enough to keep your emissions within state-mandated levels.
Loose Gas Cap
Your check engine light can also flip when you have a loose gas cap. The gas cap covers the fuel tank and normally keeps fumes in the tank so you are not wasting gas.
A loose cap may let fuel vapor escape, which will decrease your overall gas mileage.
Fortunately replacing a loose gas cap is very cheap. You will pay around $30 to have a pro do it for you.
The typical range is between $10 to $50, depending on the make and model of your car. You can most likely buy and replace the cap on your own if you are so inclined.
Broken EVAP Valve
The evaporative (EVAP) valve works to trap fuel vapor from the fuel tank and cycle it through the engine. The EVAP valve minimizes gas waste by making sure fuel does not escape in the form of vapor.
Fuel vapor and impurities can cause these valves to degrade and break down over time.
It will cost you approximately $180 on average to replace a broken EVAP valve. The typical range is between $100 and $260.
Most cars have one EVAP valve that is located either on the left side of the throttle body or around the back of the fuel tank, near the charcoal canister.
Faulty Mass Airflow Sensor
A mass air flow sensor monitors the amount of air that is entering the fuel injection system. When the ratio of fuel to air is off, the sensor modifies air intake to keep the ratio correct. Without the sensor, your engine will run less efficiently.
It usually costs an average of $260 to replace a faulty mass airflow sensor. The typcal range is between $200 to $320, depending on the make and model of your car. Most cars only have one mass airflow sensor.
Check Engine Light Diagnostic Tool Costs
If you do not want to go to a mechanic, then there are ways you can diagnose the check engine light problem. But you will need to buy an OBD II diagnostic scanner to diagnose issues on your own.
When you take your car to the shop, the mechanic will use a special scanning tool to read the computer and error code. The OBD system is responsible for producing the right code to tell the mechanic what is wrong.
The scan tool lets you diagnose the actual problem with the right code. You can buy one of these tools to save time and money diagnosing the problem yourself.
There are several types of OBD scan tools. You can buy one with a display interface or you can buy one that works via a smartphone app.
The latter kinds of scanners are usually cheaper. You can buy a decent scan tool for about $70 on average. Some scanners cost only $20 while others may cost over $100, Below is a table showing average prices for various scan tools.
| Product | Price |
|---|---|
| FOXWELL NT301 OBD2 Professional Scanner | $65 |
| Autel AutoLink AL319 OBD2 Scanner Reader | $35 |
| BlueDriver Bluetooth Pro OBDII Scan Tool for iPhone & Android | $120 |
| OBDLink MX OBD2 Bluetooth Scanner for Windows | $100 |
| FOXWELL NT604 Elite Car Scanner | $140 |
| AUTOPHIX OBD2 OM126P Enhanced Scanner | $50 |
| INNOVA 6030P OBD2 ABS Code Reader | $100 |
| THINKCAR OBD2 Scanner Car Code Reader | $30 |
| CGSULIT OBD2 Scanner Car Code Reader | $45 |
| Autel MaxiLihnk ML519 Enhanced Mode OBD2 Scanner | $60 |
Most scan tools come with the appropriate adaptor cables, but you may need to buy an adaptor, depending on the kind of connector pins your car’s computer system has.
OBD adaptor cables are cheap and usually cost between $10 to $20. You may have to search the internet to find updated error code indexes for your vehicle, though many devices come with codes for major car brands pre-installed.
Factors that Affect Check Engine Light Repair Costs
Nature of problem
You check engine light can flip for several reasons. Some may be an inexpensive fix while others might be more expensive.
For example, it will be more expensive to replace a faulty catalytic converter than an oxygen sensor or spark plug.
Make/model of car
The make and model of the car also affect costs. Some cars have specialty components that cost more to repair/replace.
For example, it will likely cost more to replace a spark plug in a BMW than in a Toyota Camry.
Age of your car
The age of your car will also affect costs. The older your car, the more wear, and tear there is on the parts, and the more likely you will have to replace multiple components at the same time.
Frequently Asked Questions
How much does it cost to repair a check engine light problem?
It will cost about $100 on average to diagnose a check engine light problem. From there, your costs will depend on the nature of the issue. Some check engine light problems can cost relatively little to fix while others can be expensive.
What is the most common check engine light problem?
The most common check engine problems are a faulty oxygen sensor, broken spark/glow plug, faulty catalytic converter, loose oxygen cap, or a broken EVAP valve.
Other common issues include a faulty alternator, a failing mass airflow sensor, or a battery issue.
Can I drive with my check engine light on?
You can, but we recommend getting the issues fixed as quickly as possible. A check engine light could indicate a small issue that will not affect performance but it could signify a serious issue that can damage your engine.
If you notice your light flashing, it means your engine has misfired and you should pull over as quickly as possible.
How often does a check engine light turn on?
The check engine light is designed to flip whenever there is a problem with the car’s systems. It is fairly common for car owners to see the light at least a few times while they own the car.
If you notice that your check engine light turns on too frequently or will turn on when there is no issue, it could be a problem with your car’s main control unit.
Is buying a check engine light scan tool worth it?
It may be worth it if you are used to DIY car repairs. Otherwise, we would recommend taking it to a professional. OBD scan tools are useful but only really helpful if you also have the tools and parts to make the repair in the first place.
Final Words
A check engine light issue can be frustrating because it is not immediately clear what the issue might be. Depending on the issue, your costs may range from just $50 to $1,500+.
If you want to save money on mechanic costs, then you could get a diagnostic scan tool and figure out the problem on your own.
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