The car signs that you must check when your car engine light is on

The 9 most prevalent problems that might cause a check engine light are listed below. 
The oxygen sensor (also known as an O2 sensor) in a car's exhaust system measures the amount of unburned oxygen. It delivers information to the vehicle's computer, which utilizes it to control the amount of air and fuel in the cylinders. Even if an O2 sensor needs to be replaced, an engine will continue to run, using more fuel than usual. A faulty O2 sensor can cause long-term harm to components such as spark plugs and catalytic converters. It may also result in a vehicle failing an emissions test. The cost of labour varies significantly based on the kind and model of the car, as well as your geographic region. Finally, keep in mind that most late-model vehicles feature dual O2 sensors.
One of the most common causes of the check engine light is a loose fuel cap. The cap is an essential component of a vehicle's fuel delivery system. It helps keep the entire system under the correct pressure by preventing gasoline fumes from leaving the fuel tank. If your check engine light comes on just after you fill up, pull over and check that the cap isn't loose — or still on the roof of your car. The cap may need to be replaced occasionally, but this isn't a problem that will break the bank.
The catalytic converter is built into a vehicle's exhaust system. It converts carbon monoxide into carbon dioxide during the combustion process. It's a relatively simple part, and its failure is frequently avoidable. Keeping your car's catalytic converter in good functioning order by doing routine maintenance (such as oil changes) on schedule is critical. If you live in the city and only drive short distances, take your car on the highway once in a while to avoid clogging the catalytic converter. Always keep an ear and eye out for strange noises or discoloured smoke coming from the exhaust.
Simply said, an ignition coil produces the electricity required by the spark plugs to ignite the fuel-air mixture in the cylinders. A single-coil is used in classic cars; however, many newer vehicles employ one coil per cylinder. A failing coil will probably trigger the check engine light, but remember that if your automobile runs on diesel, you don't have ignition coils or spark plugs.
As its name implies, a spark plug wire delivers electricity from the coil to the spark plug. The fuel and air combination in the cylinders would not ignite without it. A single wire per cylinder is used in the vast majority of automobiles. A choppy idle, a significant loss in engine performance, and lower gas consumption are all signs of faulty spark plug wires.
The mass airflow (MAF) sensor keeps track of how much air is pumped into the engine. Your automobile wouldn't be able to react to changes in altitude without it because it's part of the engine management system. A rough idle, problems are starting, and an abrupt change in the location of the throttle pedal are all signs of MAF failure. A MAF problem might also be indicated by decreased gas mileage and stalling.
If not fitted properly, an aftermarket alarm might cause serious damage to your vehicle. It can deplete the battery, cause the check engine light to illuminate, and possibly prevent the car from starting. Then, it will go off in the middle of the night because a leaf from an oak tree has fallen on the hood. If any of the above problems sound familiar, you'll need to have your alarm repaired, reinstalled, or entirely replaced by a qualified mechanic. It may cost a little extra to do it perfectly the first time, but the peace of mind that comes with having a fully operating alarm is priceless.
Every car contains a vacuum system that can be used for various tasks. The brake booster is vacuum-operated, and the vacuum system also helps reduce hazardous emissions by directing gases away from the engine as the fuel evaporates. A vacuum leak could be blamed if your car idle starts to surge or settles at an unusually high rpm. When vacuum hoses get old, they might dry out and crack, especially if they're exposed to excessive heat or cold. This most commonly causes vacuum leaks. Cracked fittings and loose connections are also prevalent problems. Although vacuum lines are inexpensive, locating the cause of the leak can be time-consuming – and costly if you don't do the work yourself.
Your car won't start, light up the road ahead, or charge your phone unless you have a battery. Batteries today last far longer than they did in the past, and they don't require any maintenance. The cost of a new one is determined by the sort of vehicle you drive. It's pretty simple to change or charge a battery on your own, but keep in mind that in some late-model cars, the battery is buried beneath a slew of plastic covers and may be tough to reach. It's also worth noting that unplugging the battery will usually reset your stereo. Ask your local dealer for the code before unbolting the positive and negative terminals if you don't have it. You'll be driving in silence if you don't.
The check engine light gives you a sense of what's wrong with your car - sometimes precise, sometimes hazy. However, it does not take the role of a qualified mechanic or periodic maintenance. Put another way, don't put off car maintenance until the check engine light turns on.