Why Does My Check Engine Light Come On and Off

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Your car’s Check Engine Light feature is a kind of warning system that alerts you whenever it senses any potential issues with your vehicle. Although it can be quite frustrating to deal with the issue at first, it may help to understand why is it occurring first.

This blog post explores the several common causes of a flickering check engine light and what can you do to diagnose and fix the issue once and for all. Depending on the severity of the issue, you may either have simple fixes like tightening a gas cap to complex ones like failing catalytic converter.

We’ll be covering it all up to help you get back on the road in no time. So, if you’re wondering why your vehicle’s check engine light is flickering erratically, make sure you keep reading to find the exact reason why.


What Does Check Engine Light Mean?

The Check Engine Light is a warning system that works on your car’s onboard diagnostic system and informs about any issues with your vehicle. However, when the indicator is flickering on and off, it may indicate a more potential issue, especially related to the engine.

The engine consists of a set of cylinders that burn gasoline to propel the vehicle. In case either of these cylinders fails, the engine could misfire. That being said, there can be various malfunctions that the check engine light could indicate.


9 Reasons Why Your Check Engine Light Keeps Coming On and Off

Existing Issue with the Check Engine Light

The check engine light is intended to stay turned on until the issue has been detected is fixed. It is designed this way to help the driver identify if their car is functioning well or not at just a single glance. However, if it’s flickering, chances are the light itself might be damaged.

Faulty Spark Plugs

Issues with spark plugs are often seen alongside the ignition coils and they’re also linked to similar symptoms, such as poor fuel economy, engine misfiring, engine surging, and slow acceleration. In case of such an issue, you may have to get your car’s spark plugs replaced or repaired by a mechanic.

Malfunctions in Ignition Coils

Problems related to the ignition coils can easily turn into a host of issues that may keep triggering your check engine light as well. It’s easy to get past the root cause of the issue in this case as a lot of precision is required to work with the correct diagnostic tool to identify the issue.

That being said, the check engine light will keep flashing on and off until you get your ignition coils fixed.

ECU Not Being Able to Store Fault Codes

The electronic control unit in your car stores fault codes that help the check engine system determines whether it has to keep alerting the driver or not. In case this particular component isn’t storing any fault codes, the check engine light may not function correctly.

It also might be possible that the ECU got reset while storing a fault code without diagnosing the error code with an OBDII scanner first. That’s why the check engine light may be repeatedly alerted about an issue with the engine and disappear when it doesn’t detect any.

Problem With Your Car’s PCM

The Powertrain Control Module, or PCM, in your car monitors and tests the efficiency of your ignition, emissions, and fuel. While the PCM is performing one such regular test, if any component marks fail once or twice then the PCM light will turn on to alert the driver.

If the issue isn’t fixed, the light might turn off temporarily but will turn back on again, indicating that there might be a fault with your vehicle’s PCM. Therefore, you should consider getting it fixed to get rid of the intermittent turning on and off of your check engine light.

Recurring Issues with The Engine

While there can be a number of reasons why the check engine light is turned on, the system doesn’t even specify one of them. Due to this, you may get one problem fixed but another issue pops right into your vehicle, and your PCM alerts you again.

One way to prevent this issue is to look for any signs of loss of fuel economy, difficult accelerations, and rough idle early on in your car. If you see any of these issues with your vehicle, consider getting it diagnosed by a professional.

The Fuel Vapours Might Be Escaping

The fuel vapor in your vehicle may escape due to a loose or broken gas cap, which may eventually trigger the check engine light. In normal operating conditions, the light is intended to stay turned on until it detects that no fuel vapors are leaking anymore.

However, if there’s an irregular leakage pattern in the fuel vapors, the check engine light may turn on and off repeatedly when the PCM detects it in its tests.

Worn Out Vacuum Hoses

If you’ve been using your vehicle for quite a time now, then chances are that its vacuum hoses might be worn out. They can also die early off their age due to poor maintenance, and while they’re deteriorating, they may keep triggering the check engine light.

The Gas Cap Might Not Be Fitted Properly

The check engine light may also flicker due to minor issues like the gas caps not being fitted correctly. There may also be a slight chance that the cap is worn out or isn’t compatible with your car, which is why it may get loose every now and then.


What To Do If You’re Struggling with This Issue?

It’s common to be unsure about what you’re supposed to do next when you encounter such a problem, especially if you’re new to cars. However, regardless of whatever you do, make sure you don’t try to just get away with it.

You see, while the check engine light does not always indicate an issue worth panicking about, you should definitely not ignore the warning just because of this sole reason. You should try to get the issue diagnosed and fixed instead to prevent future problems.

The best course of action is to first get your car diagnosed by a local mechanic and identify the root cause of the problem. In most common cases, the check engine light issue may trigger a die to the powertrain, engine transmission, and other related components.

Final Words

So, as you may have read above, there can be several reasons why your car’s check engine light keeps turning on and off intermittently. The best way to deal with such issues is to prevent driving your vehicle for a long and get it repaired by a professional first.

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