why is my check engine light on

Ultimate Engine Light On Guide  – Meaning, Causes, Reset and FAQs

When a car’s engine light turns on, many people ignore it while hoping it’s not a big issue. While minor problems often activate a check engine light (malfunction indicator light – MIL), serious issues often do so also, and not addressing the problem can lead to expensive repair bills. More than 15% of vehicles on the road have their service engine light on.

But, what does it exactly mean when your check engine light goes on? Is it dangerous, and what should you do about it? Keep reading, and you’ll get answers to all your questions.

What Does Check Engine Light Mean?

If the check engine lights up, it’ll either blink or stay constant, depending on the issue. Anyway, you should have the vehicle checked by a qualified mechanic as soon as possible. If the light is steady. The problem isn’t an emergency, but you should schedule an appointment ASAP.

A flashing check engine light usually signifies a severe engine misfire letting unburned fuel to be delivered into the exhaust system. There it can rapidly increase the temperature of the catalytic converter to a point where damage is likely, needing a costly repair. If this happens, you should reduce power and have the vehicle checked right away.

Today’s car computers often attempt to recoup when there’s an issue. So, you may not see deterioration in performance, although your fuel mileage is suffering, and your vehicle may be emitting higher levels of hydrocarbons and other pollutants.

Why Is My Check Engine Light On?

The malfunction indicator light may be indicating an issue that’s easy to fix – like a loose gas cap that should be replaced. It could also be a signal of a severe issue that could ruin your engine components.

MIL blinks on glows, depending on what’s wrong with your car. A check engine light flashing signifies that your vehicle’s engine is in serious trouble. In contrast, a steadily lit one means less urgent service is required. However, it’s easy to find out what the problem is, and taking care of it without delay can save you money and prevent further damage.

Main Reasons for Check Engine Light On?

Don’t ignore your vehicle’s warning system. The orange engine light can be activated by several problems of varying degrees of severity.

Follow the list of the top 10 reasons why your check engine light came on.

  • Faulty oxygen sensor – A bad sensor can’t adequately measure oxygen in the exhaust to inject the proper amount of the fuel to the engine, causing a vehicle to lose up to 40 percent of its mpg;
  • Loose gas cap – Fuel system sensors could be triggered if there are vapor leaks in case you have a loose gas cap;
  • Malfunctioning catalytic converter – A new catalytic converted is needed if something else in the engine needs repairs and the exhaust is laded with oil or gas;
  • Faulty ignition coil – If the ignition coil is compromised, then there can be no spark to start the engine. Coils can go bad during time of operating in high temperatures;
  • Bad spark plug – This means your car isn’t firing on all cylinders and ultimately, you’re wasting gas;
  • Bad MAF sensor – It measures the inflow of air to the engine. A lousy sensor could mean your engine efficiency is reduced by up to 25 percent;
  • Non-compatible aftermarket alarm – Only install compatible components and accessories in your vehicle by a certified mechanic;
  • Leaky hoses on EVAP system – They cause evaporating fuel to not reach its vented destination;
  • Faulty EGR valve – This valve is responsible for pushing the exhaust back through the combustion process and help lower emissions;
  • Battery charging problems – More advanced monitoring systems can detect issues with your car battery.
reasons for check engine light

What to Do When the Check Engine Light Goes On?

Not all malfunction indicator light warnings are engineered equally. Here are 4 common scenarios, and what they mean:

1. The check engine light goes on only in certain cases

If light comes on in the city but goes off on the motorway, then the problem is only occurring in city driving conditions. Pay attention to whether or not the car runs/drives any differently when you notice the light. If you see a difference, drive the vehicle as little as possible and take it to the mechanic.

If there’s no change in engine performance, you can drive home, but have it inspected right away. In this scenario, you run a risk of the car dying or not starting.

2. The MIL comes on and remains on

If the light is on always during driving with no noticeable driving or performance issues, there’s a permanent error in the emission control system. When this occurs, the computer that controls the emissions system will usually make it, so your vehicle runs only in a few lower gears — this’s known as “limp-in.” It would be best if you got the car serviced ASAP.

3. The malfunction indicator light blinks stays on, and there are performance issues

It means that a critical component of your emission control and engine management system has a severe problem. It usually involves a component or system required for the vehicle to run at all. In many cases, the car isn’t safe to drive at all — it could stop or stall out at any time. It’s recommended to pull over to a safe place and have the car towed to a repair shop for a thorough inspection.

4. The check engine light goes on and flashes in a steady pattern while driving

Don’t confuse this constant pulsing of the MIL (usually one or more flashes per second) with a flicker. It may remain on steadily, or it may flash when the car is accelerated. This’s very serious.

There’s a severe failure of the emission control system that’s causing the motor to misfire to the phase that the catalytic converter is damaged each time the light blinks. It could mean that the catalytic converter is overheating to the point that it’ll glow red or, in extreme situations, start a fire on the underside of the car. Automatically pull over to a safe place and have your car towed to an car diagnostic for repair.

How to Reset Check Engine Light?

Cars are equipped with electrical systems that supervise how the car is working. When something’s wrong, a little light “jumps” on your dashboard that tells, “Check Engine.” There are 3 main ways to go about clearing/resetting the engine light. We’ll break them all down and illustrate how to perform each one step by step.

check-engine light flashing

1. Use a code reader or scan tool

This option is the most efficient and detailed. A scan tool won’t only clear the service engine light, but will also let you see why light is on in the first place.

  • Locate your OBD port and plug your scan tool into the OBD port and turn the key on the position;
  • This step will vary based on the device you’re using, but select “Read” and scroll through the codes that are active on your car. Write down codes if they come back or change later down the road;
  • Choose “Clear” and clear the MIL codes. At this stage, the malfunction indicator light should be off, and you have successfully cleared your service engine light. If the light returns, you’ll have to diagnose and repair the concern that’s causing the code.

2. Disconnect battery

This method is easy to do, and most people have the tools to perform it, but it’ll reset seat memory, clock, and radio presets.

  • Locate your car’s battery. For most models, it’ll be located under the hood, but for some, it may be located in the trunk or in other areas of the car;
  • Disconnect the negative terminal (cathode) of the battery. It’ll be usually labeled with a (-) negative symbol and colored black;
  • Touch the negative cable end, and you just disconnected to the positive terminal still connected to the battery. The positive terminal (anode) will be labeled with a (+) positive symbol and colored red. Hold it there for 60 seconds. This will fully drain the cars capacitors and fully reset at the vehicle systems;
  • Reconnect the battery terminal end(s) and connect the positive terminal first (if removed), followed by the negative.

3. Switching on and off the ignition

Turning on and off the ignition is also one of the methods of hard reset without disconnecting batteries. Put keys your ignition and switch on and off your ignition in succession after an interspace of second in each step. Once it’s done, check if the engine check light is still coming or not. If the light is off, then you’re good, but if it’s still on, schedule an appointment to a certified mechanic as an issue could be quite serious.

4. Drive the vehicle until the light goes off

This technique doesn’t always work, but it can in some situations. Drive the car for approximately three days and allow the vehicle to do its own self-check. If computer decides the issue has been resolved or is no longer a problem, it’ll turn off the engine light itself. In case, the light comes back, you’ll have to diagnose and repair the “reason” that’s causing the faulty code.

check engine light codes

Engine Light FAQs

Can I Drive Car if the Check Engine Light is On?

If you don’t see check engine light blinking, you may safely drive the vehicle to the car repair shop for service, but it shouldn’t be driven much farther. Never drive if the MIL is flashing!

How to Turn Off the Check Engine Light?

Most code readers will enable you to turn off or reset the engine light. But this operation alone doesn’t actually fix the underlying problem. In many situations, the light will come back on later.

Why Do I Need to Check Engine Light On After Oil Change?

Oil changes are crucial maintenance for your vehicle, but it won’t do anything that could cause your MIL to come on. If you see the light after an oil change, something else is wrong. Still, your mechanic has the necessary tools to run tests and get to the bottom of what’s wrong.

How Much It Costs to Diagnose and Repair?

It’s difficult to say precisely how much a diagnosis will cost. Typically, the diagnosis itself will be less than $100. The repairs you need may cost more, but they can potentially save you a lot of money in the long term.

check engine light blinking

Can a Bad Air Filter Trigger a MIL?

In extreme situations, a contaminated air filter can turn on the yellow engine light. An ultra-dirty air filter reduces engine air intake. It disrupts the air/fuel mixture inside the engine. Therefore, the car may experience performance issues that cause the check engine light.

Is the Maintenance Required Light and Check Engine Light the Same Thing?

No. The “Maintenance Required” light is a reminder from your car’s computer that it’s getting close to the time for an oil change or other preventative maintenance services. The malfunction indicator means that your vehicle’s computer has detected there is an issue with your car.

Magic Auto Center – #1 Santa Clarita Engine Diagnostic

We’ve been providing excellence in quality car care in Santa Clarita Valley since 1997. Our shop employs ASE certified technicians, and equip them with today’s latest automotive diagnostics technology. We’re armed to handle all major and minor repairs on European, Domestic, Japanese and exotic cars on the road today.

Need a brake service, wheel alignment, car battery service, oil change, or vehicle repair of any kind? Call the leading Santa Clarita Auto Repair shop at (661) 291-1232 or book an appointment below!


    Choose the preferred date and time.
  • MM slash DD slash YYYY
  • :

    Select the services you need or tell us more in the section below.
  • This field is for validation purposes and should be left unchanged.
© Copyright 2024 Magic Auto Center | OrganicSoft SEO