Why does my check engine light come on and off? What to do?

Check Engine light comes on.

When your car’s Check Engine light illuminates your dashboard, it’s usually accompanied by the fear that you’ll have to spend a lot of money on repairs. But it can also mean a minor problem, such as a faulty gas tank lid, or mean something more serious, such as an engine misfire.

In many cases, this means that you will visit an auto sales and service centre to fix the problem and reset the warning switch.Engine warning switch, more commonly known as a fault display, is a signal from an ECM (Engine Control Module) that something has gone wrong.

Automakers began to standardize their systems from 1996 cars under the OBD-II protocol, which established a list of diagnostic trouble codes (DTC) and required all cars to have a multipurpose data link connector to access this information.

The connector is usually located under the steering column and is relatively easy to access. Until 1996, automakers had their own engine diagnostics systems, primarily to ensure that their vehicles met EPA pollution control requirements.

The engine warning lights are orange or yellow, depending on the manufacturer. However, if the warning switch starts flashing, it indicates a more serious problem, such as a misfiring, which can cause quickly overheat of the catalytic converter.

Deciphering the code

Some drivers may confuse the maintenance light with the engine check warning light. These warning lights are not connected. The maintenance light indicates that the car needs to have its oil replaced or other regular maintenance performed. This is not a fault display, like an engine check light.

Your local mechanic can usually diagnose the problem. But there is a way to see beforehand what the problem might be. You can buy an inexpensive code reader from an auto parts store or an online store that connects to the on-board diagnostic (OBD) port, and then find the fault code online. Modern systems display the code in an app on your smartphone.

How to turn off the engine check light.

Most code readers allow you to turn off or reset the engine check light. But by itself, this action does not rectify the main problem. In many cases, the light simply turns on again later.

Mixed signals

But even with the code and its meaning, interpreting it yourself can be a little tricky – even if you understand something about the mechanics.


“My wife’s car started to run poorly and the engine light came on. My code reader has detected a trouble code for the angle of rotation sensor. I thought I could buy a sensor and install it myself. But if I did so, I would have wasted the money on the sensor. It turned out that it was not the sensor itself that was broken, but the wire going to it, which is much cheaper,” our reader told us.


According to the chief automotive engineer, sometimes the light is up when the car is all right. This may be a temporary problem caused by changes in humidity or other factors. In such cases, the light should go out on its own after a short time.

Do not ignore this light

Some people are horrified when they see the Check Engine light. They just stick a piece of black tape on the dashboard light and keep going. It is important to quickly solve the problems reported by the light. Ignoring them later can lead to more serious and costly problems.


If the light comes on, the first thing we suggest to the driver is to check the gas tank lid. A loose gas tank lid sends an error message to the car’s onboard computer, reporting a leak in the vapor capture system, which is one aspect of the car’s emissions system. If the fuel tank lid is loose, tighten it and continue driving. Even so, he said, it would take some time for the lights to go out.


What should you do if the engine check light is always on instead of blinking? The most obvious answer is to ask the mechanic to check the engine. But many people don’t do anything, perhaps fearing a repair bill. Some drivers with older cars may want to run as many remaining miles as possible without visiting the service. But before they can pass the vehicle inspection, they must get rid of the Check Engine. And a vehicle inspection is a good motivator for solving a problem.


The system is primarily designed to continuously monitor the vehicle’s exhaust gas system throughout the vehicle’s entire life of vehicle. However, the car mechanic notes: “The engine and the emission control system are so interconnected that the serviceability of the emission control system is a good indicator of the overall condition of the car engine.

Even an inexpensive engine code reader can be useful to car owners, even if they are not interested in auto mechanics.


“If the mechanic gives you the same information, at least you know that he is not deceiving you,” the expert notes. The code reader provides car owners with information to help talk to their mechanic and avoid costly or unnecessary car repairs.



What to do if your car's computer detects the P0301 error code - one engine misfire in cylinder 1 .

When combustion does not occur in one or more cylinders, this leads to misfires in the engine, it is easier to say to miss the ignition.

Driving a car in this condition leads to the ingress of unburned fuel into the exhaust system and, as a result, into the catalytic converter. It is not intended for purification of exhaust gases.


These exhaust devices operate at high temperatures to reduce emissions, but can pose a fire hazard if malfunctioned.

It is important to correctly diagnose the cause, as the cost of repair depends on the severity of the problem.

Engine misfire symptoms

  • Engine rough idle
  • The smell of unburned fuel from the exhaust pipe
  • Lack of power during acceleration
  • Jerks when the car accelerates, the engine gets stuck and flutters
  • The Check Engine warning light on the dashboard is on continuously or blinking
  • High fuel consumption
  • Intermittent engine operation


  • Low fuel pressure
  • Faulty fuel injectors
  • Low compression in cylinder 1
  • Faulty O2 air flow sensors
  • Leaky cylinder of Main cylinder module gasket
  • he vacuum hose is cracked or disconnected, the pipe duct is damaged
  • Vacuum leak
  • Distributor cap wear
  • Valves burning-out
  • Damage to the cylinder 1 spark plug

What will help you fix the error P0301

  • Read all error codes with the OBD-II scanner.
  • Erase all the error codes from the PCM memory and perform a test drive to find out if the P0301 will appear again.
  • Inspect the spark plug wire of cylinder 1 and check it for damage and wear.
  • Do the same with the spark plugs and coils. If necessary, change them and the their corresponding wires.
  • If this does not help and the code P0301 appears again, check the fuel injector and the wires for damage.
  • Inspect the ignition distributor cap and slider for damage and corrosion.
  • Take a test drive again to see if the P0301 reappears.
  • Then check the compression in cylinder 1.
  • If the error persists, the problem may be related to a malfunction of the PCM. In this case, reprogramming the module will help.