If you notice your check engine light flashing, you shouldn’t ignore it as it could signal an issue that should be repaired as soon as possible. But what does it mean? The light could mean several different issues. We’ll explain the common reasons why the check engine light turns on and run through preventative maintenance tips to avoid future issues.
What Does the Check Engine Light Indicate?
The Check Engine Light (CEL) is also known as the Malfunction Indicator Light (MIL). It's a warning light on your car’s dashboard and it lights up to indicate an issue with your car’s engine or emission system. It turns on when something in your car’s performance is unexpected but it doesn’t always signal an emergency. If it is flashing, it usually means the issue is more serious than when it is steady.
How the On-Board Diagnostics (OBD) System Works
The OBD system is a computerized network that monitors your car's performance, continuously checking for any issues. It does this through a series of sensors in your car, when it detects a problem it activates the CEL.
Common Reasons Why the Check Engine Light Turns On
There are many reasons why the check engine light illuminates, here are some of the most common:
- Loose or Faulty Gas Cap: The gas cap keeps fuel securely inside the car’s tank until it’s needed. If it’s loose, fuel can escape. If the CEL is on after refueling, you may need to tighten the gas cap.
- Faulty Oxygen Sensor: The oxygen sensor measures the oxygen remaining after the air-fuel mixture ignites. If it detects an issue with oxygen use or burns out over time, the engine may receive too much or too little oxygen which can lead to poor fuel economy and long-term damage.
- Catalytic Converter Issues: The catalytic converter transforms harmful chemicals into safer ones. When it malfunctions, the car’s emissions system can cause toxic fumes to be expelled. Catalytic converters are designed to last, so when they fail, it could suggest a more serious issue.
- Mass Airflow Sensor Problems: The mass airflow sensor ensures the proper air-fuel mixture and measures the air entering the engine. When it fails, it sends misinformation to the engine control unit, which leads to poor engine performance.
- Spark Plug and Ignition Coil Failures: For gasoline engines, the heat needed to ignite the fuel in the combustion chamber comes from spark plugs and the ignition coil. These can deteriorate over time, leading to a mistimed or faulty ignition. It can also lead to increased emissions and or suggest an engine misfire, where one or more of the engine’s cylinders fails to fire properly.
- Issues with the Battery or Charging System: The CEL may turn on if the battery has low voltage or corroded battery terminals. It may also suggest alternator issues, which could overcharge or undercharge the battery. If there are issues with the battery or charging system you may experience flickering lights, slow engine crank or electrical component failure.
What to Do When Your Check Engine Light Turns On
Step-by-Step Guide to Diagnosing the Issue
It can be difficult to know how to address a turned-on CEL, but here are a few steps you should take to help diagnose the issue:
- Don’t wait: It’s important not to delay addressing a lit CEL. Even if the issue is minor, delaying any investigations may lead to more significant problems.
- Look for the obvious: Check your car to see if the CEL is lit because of something obvious like a loose gas cap. If this is the case, you might be able to remedy it immediately.
- Observe: Make a note of how your car is performing. If something seems off like strange noises or poor acceleration, it may be a sign of a larger issue.
- See a professional: It’s always best to check with a mechanic to properly diagnose and fix the issue.
Using an OBD-II Scanner
An OBD-II scanner is a device that plugs into your car’s OBD-II port, which is usually located under the steering column. It generates OBD-II codes, or trouble codes, which can tell you exactly what’s wrong with your car. You can generally go to an auto parts shop like AutoZone and they’ll be able to let you use an OBD-II scanner for free.
The OBD-II scanner can analyze issues with your car once you turn on the ignition, but without having to start the engine. The scanner will retrieve diagnostic trouble codes after communicating with your car's onboard computer. These codes will appear on the OBD-II scanner which you can then interpret in the scanner’s manual or online. Sometimes multiple codes might appear which may all be related to the same problem.
When to Seek Professional Help
You must know when to get help from a professional:
- Flashing CEL: This usually indicates a serious issue that may cause major damage to the engine if not addressed quickly.
- Unable to identify the problem: If you are unable to locate the issue, it’s time to speak to a mechanic as they know to correctly diagnose the problem.
- No scanner: If you don’t have an ODB-II scanner it’s best not to guess and seek advice from a professional.
- Complex issues: If you identify a complex problem, it’s best not to repair it yourself and instead have your car fixed by a professional mechanic.
The Difference Between a Steady vs. Flashing Check Engine Light
A steady CEL usually indicates that the issue is not an emergency. While you should never wait too long to address any issues, it is often safe for you to drive your car home or to a mechanic. A steady CEL might indicate issues with a loose gas cap, faulty oxygen sensors, minor misfires or emission system problems.
If the CEL is flashing, it may suggest a severe engine problem like engine misfire or severe fuel or ignition issues. These can damage the catalytic converters and subsequently cause more severe problems. It is advisable to stop driving as soon as possible as continuous driving while the CEL is flashing may cause significant damage to a car’s engine or exhaust system. It is recommended to seek professional help immediately in this scenario.
How Much Does It Cost to Fix a Check Engine Light Issue?
Common Repair Costs and Estimates
A lit CEL may suggest many different repairs that can range from twenty to a thousand dollars, let’s look at these cost estimates from lowest to highest:
- Tightening or replacing the fuel cap: $24.84
- Reprogramming the powertrain control module: $109.22
- Replacing the evaporative emissions purge control valve: $137.47
- Replacing the ignition coils: $213.70
- Replacing the thermostat: $238.58
- Replacing the oxygen sensor: $242.34
- Replacing the mass air flow sensor: $303.61
- Replacing the ignition coils and spark plugs: $392.65
- Replacing the fuel injectors: $423.71
- Replacing the catalytic converter: $1,313.46
DIY Fixes vs. Professional Repairs
Fixing your car yourself will often be significantly cheaper than at a mechanic as there will be no overhead costs, however for more complex issues it’s always advised to seek professional help so that the problems are adequately addressed.
Preventative Maintenance Tips to Avoid Future Issues
Routine Inspections and Tune-Ups
Regular maintenance will ensure that your car is continuously performing at its best and keep potential issues at bay. Moreover, if your car is regularly seen by a mechanic, they’ll be able to identify minor issues before they grow into major problems.
It’s advised to follow the maintenance schedule outlined in your car’s owner manual to ensure it’s well maintained. Regular maintenance to avoid the CEL switching on include checking and replacing spark plugs, inspecting the ignition system, inspecting the fuel system, and changing the air filter.
Keeping Your Fuel System Clean
A clogged fuel system may trigger the CEL. A clean fuel system is not just vital for your engine’s health, but also helps to ensure smooth operation, lower emissions and proper fuel efficiency.
It’s advised to use a high-quality fuel as this will help prevent deposits and clogs in the fuel system. You may also consider using a fuel injector cleaner every 3,000 to 5,000 miles as these help keep the fuel injectors free from carbon deposits, improving fuel flow and combustion efficiency. It is also recommended to replace the fuel filter every 30,000 miles as a clogged fuel filter could cause engine hesitation or misfires.
Monitoring Battery and Alternator Performance
Your car’s battery and alternator are critical to its electrical system, if they are experiencing problems these can lead to serious issues.
It’s advisable to have your car’s battery tested at least once a year. You should also ensure the battery terminals are tight, clean and free of corrosion as this may cause poor connections and voltage fluctuations. In addition, you should inspect the alternator if you notice dimming lights or noises from the engine as this may suggest it’s failing and causing electrical issues.
Car batteries usually last up to five years so if it’s reaching this age you may want to consider replacing it before it fails and causes electrical problems.
Final Thoughts: Don’t Ignore the Warning
If the CEL is lit, it’s for a reason. While it may signal a minor issue, it could also indicate something more serious. The sooner you address the issue, the less likely your car will suffer from major damage.