Every modern car has an engine-shaped warning light, which activates when something is wrong with your engine or other systems. It can mean anything from a loose gas cap to a blown head gasket, which is why vehicle owners often joke about this light being one of the most annoying things ever. Owning a car is much easier if you understand why the check engine light comes on and how to deal with it.
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Check engine light: flashing vs. static
Depending on the severity of a situation, the check engine light can either flash or remain static.
A static check engine light warns about the need for servicing. Even if you don’t experience a loss of power or unusual noises, you should visit a repair shop as soon as possible when the check engine light comes on. You can drive with a check engine light on but you should postpone unnecessary driving to avoid further damage and safety risks.
A flashing check engine light warns about more serious problems that can’t wait, such as misfiring cylinders, low oil pressure, or incorrect combustion cycle. It means that a car needs immediate repairs, therefore you should pull over and tow a vehicle to a repair shop. Driving with a flashing check engine light can severely damage a car’s engine and other components.
How to reset the check engine light
Many drivers think fault code readers can solve issues by simply erasing codes. Unfortunately, these scanners are only diagnosing tools and someone still has to fix any revealed problems. Here’s how to reset the check engine light properly:
Scan for trouble codes
Modern cars have advanced electric systems that you can scan using a trouble code reader. Most mechanics have these tools and will help you. Remember that not all scanners are equal – their cost varies between $10 and $20,000, with the more expensive options having more features, and providing faster/more precise operations.
The market is full of inexpensive code readers, meaning you can obtain the fault codes yourself. You only need to locate your car’s OBD II port (most commonly found beneath the steering wheel column), connect your tool, scan the vehicle, and see what codes come up.
You can research the codes on the internet for a more detailed explanation and potential solutions – this should give you at least a brief idea of the issue.
Diagnose the problem
Diagnosing the problem is more complicated than revealing the faults. If you’re lucky, a fault code will lead you straight to the problem. However, more often it will only tell you that, for instance, the fuel pressure is too low. In turn, this could signal anything from a dirty fuel filter to a worn out fuel pump.
Here are the most common trouble spots with their respective fault codes:
Faulty mass airflow sensor (P0101)
A mass airflow sensor (MAF) measures the amount of air entering your engine, and the engine control unit (ECU) uses this data to provide the engine with the correct amount of fuel.
Faulty oxygen sensor (P0131, P0134)
It measures the proportion of oxygen to gas inside a vehicle’s exhaust system to determine the correct air-fuel ratio. You may notice a significant drop in fuel economy when this sensor fails.
Loose gas cap (P0455, P0457)
When a car detects fuel vapor escaping the tank, a loose gas cap is one of the most common issues. The gas cap may even be faulty, meaning you’ll need to replace it.
Vacuum leak (P0171, P0174, P2279)
Vacuum leaks can cause many issues, triggering various fault codes. Some cars require there to be a vacuum to control the brake booster, turbocharger, or to adjust the air-fuel mixture. As a result, “lean air-fuel mixture” fault codes are common.
Stuck EGR valve (P0401)
An exhaust gas recirculation (EGR) valve reduces emissions by letting exhaust gasses pass into an air intake manifold for repeated use. This valve often sticks or fails, resulting in a loss of power and the P0401 fault code.
Engine misfire (P0300)
An engine misfires because of worn spark plugs, spark plug wires, or fuel injectors. It causes rough idling, a loss of power, and excessive fuel consumption.
Catalytic converter failure (P0420)
The catalytic converter filters out harmful particles and burns them up, significantly reducing emissions. It burns out or clogs up over time, triggering the check engine light.
These are only a few of hundreds of possible fault codes, therefore, good knowledge is essential when working on modern cars. After obtaining the diagnostic trouble codes, a mechanic usually performs a live data check to determine which readings are out of order and which components should be inspected.
Fixing the revealed problems means replacing broken parts and sensors, repairing wires, or cleaning electrical terminals. You could scan the fault codes and perform a few basic checks yourself. However, most repairs require special tools and knowledge, so you should leave them to professionals.
How do I know if my check engine light is serious?
The check engine light shouldn’t be ignored because most of the related issues affect a car’s performance and longevity. A blinking (or red in some cars) check engine light warns about issues that require you to stop your vehicle immediately, while a static light means you can drive to a repair shop. Either way, you need to check the engine fault codes to address the problem.
Bear in mind that most of the serious issues occur due to a lack of maintenance, therefore, proper car maintenance is needed to keep your car’s condition in top shape. For instance, oil changes extend the lifetime of your engine, a fresh coolant prevents overheating, and a new battery prevents internal damage. Those who follow a proper maintenance schedule have a much lower chance of facing major car problems.
What is the most common reason for the check engine light?
Issues with the emissions system is the most common reason for the check engine light. They are often caused by inefficient catalytic converters, leaking exhaust, or a faulty EGR system.
Can I drive with the check engine light on?
You can drive with the check engine light on, but you should visit a repair shop as soon as possible. However, you should stop driving immediately if the light is blinking or red.
Why is my check engine light on, but nothing seems wrong?
Faulty sensors, vacuum leaks, and other issues may not show any immediate signs but will affect the engine’s performance and eventually damage the internals and other systems.