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Check engine light on again? These are the top reasons that pesky light is glowing

There seems to be a prevalent conspiracy theory among many drivers out there that the check engine light is just a creation of the auto-repair companies to siphon your money from your wallet. If that is true, then we are unaware of such malevolence. We do know, however, a more logical reason that you may be seeing warning lights on the instrument cluster.

A lot of you probably just ignore the check engine light when it comes on. But the check engine light can be triggered by a number of issues. If you ignore these issues for long, they cause further, more costly problems. Owning a car, whether we like it or not, is a responsibility that requires some minor attention now and then in order to avoid a serious problem. If you really think about it; wouldn’t you want to keep your car, the thing in which you routinely travel above 60 mph, in good operating condition? Your life is on the line, after all.

We did our research and found out exactly what the most common reasons for a check engine light coming on are. One thing many of you might not be aware of is that if the light starts flashing, then it’s a more serious problem. Sometimes, though, an illuminated check engine light is something as simple as  gas cap that needs to be re-tightened real quick. Other times, however, you have to take it into the shop.

Luckily for you, companies like AAMCO will do a diagnostic on your car for free if the light comes on. You can also buy your own checker to find out what the problem is yourself. Here’s the list of the top 10 reasons that annoying little light is bothering you. Thanks to CarMD’s 2013 Vehicle Health Index for the help. These are listed in order of prevalence.

1. Oxygen sensor failure

oxygen sensor

Oxygen sensors essentially check to make sure the ratio of fuel to air is correct. When there is too much fuel or too much oxygen going into the engine, the use of this sensor can allow your car’s computer to equalize the issue. Oxygen sensors fail somewhat frequently, this is why it is the most common reason for your check engine light to go on. The reason your sensor might fail is because you’ve neglected taking care of your car or from using gas that is high in ethanol. Besides the obvious reasons that your engine not receiving the correct ratio might be a problem, one of the most serious ramifications of a sensor failure is losing almost half your car’s fuel efficiency (which costs money by itself). 

2. Your gas cap is loose, fool. 

gas cap

If your gas cap is just loose because you’re negligent, then it shouldn’t cost you anything to tighten it. What you do is, get out of your car and tighten it (when the vehicle is stopped). However, if your gas cap is damaged and needs to be replaced, you’re looking at spending a few bucks. A messed up gas cap situation accounts for over seven percent of the situations that a check engine light goes on, which is actually quite a bit higher than a lot of other reasons. You should hope, just hope, that the gas cap is the problem. A lot of other problems will hit your wallet much harder. We recommend you try tightening it first and then see if the light goes off.

3. Catalytic converter trouble

catalytic converter

Catalytic converters ain’t cheap. Having to replace a converter is one of those things you’re hoping is not the case when that check engine light comes on. The converter is part of your exhaust system and turns toxic gases into mostly harmless exhaust. Bad exhaust valves, bad spark plugs, and anything that causes the exhaust gases to be the wrong temperature or consistency can make a converter fail. Not only does it cost a lot to replace converters, there’s probably another underlying problem that caused it to fail, which will cost more money to fix. You should hope, just hope, that this is NOT the problem. However, don’t let the fear of your converter being the problem stop you from getting your car checked out. Your car could start releasing toxic fumes all over the place.

4. Bad spark plugs/ignition coil

spark plugs

So … something made your catalytic converter fail? Maybe it was your spark plugs and ignition coil or coils? Well, plan on spending another $300 to fix that. For those of us that don’t know, the ignition coil charges the spark plugs by converting low voltage electricity from the car’s battery into high voltage electricity that can get the plugs going. Both coils and plugs can fail just from the amount of high temperatures they’re exposed to, as well as due to general aging. If your car stops running or won’t stay running, it might be the plugs/coil, because the plugs aren’t getting enough electricity to ignite the combustion to run the engine. Plugs typically range from $20 to $60 each, your ignition coil would cost $30 to $50 or so, and the labor will probably cost the most. That is if you have a car that uses only one coil. Most cars built from the late 1990s and on use one coil per cylinder. If you have one or several bad coils causing engine inefficiency, you’re looking at a higher repair bill. Sorry.

5. Bad spark plug wires

spark plug wires

Have you ever heard your car idling a lot louder and rougher than it used to? It might be the spark plug wires. When these babies start to erode the electricity becomes less consistent and makes it hard for the engine to stay running, especially when idling. Spark plug wires is a similar problem to the ignition coil/spark plug problem, but the labor for replacing the wires can be more pricey in some places. Bad wires can also cause your car’s fuel efficiency to go down, which, again, will cause you to lose money in the first place.

6. Your mass air flow sensor is jacked up, son.

mass air flow

The mass air flow sensor figures out the barometric pressure, humidity, of the air going into your engine’s combustion system. The sensor works in collaboration with your oxygen sensor. You car wouldn’t be able to adjust to changes in altitude and outside conditions without it. Needless to say, you need the sensor to keep your car running; and it’s not cheap. Failing to replace a mass air flow sensor can cause your car to lose gas mileage – up to 25 percent. There are a lot of symptoms that your sensor might be failing, including a rough idle, trouble starting, and unexpected change in the position of the throttle. The symptoms may sound familiar, as they’re similar to what happens when the plug wires are failing, which is why you need a professional sometimes.

7. Janky aftermarket car alarm system

car alarm

There can be a lot of issues with the installation of aftermarket car alarm systems, and they can mess up your car. Depending on how it was installed, problems with an alarm system can range from draining the car’s battery to preventing the car from starting. The person who installed it, possibly you, might have failed to connect the wire correctly or done shoddy connections. Sometimes the problem is simple as not even installing the correct parts. You will need to have the system reinstalled or replaced, and you will have to get anything fixed that might have been damaged by the problems it was causing. If you’re considering getting an aftermarket car alarm, consider spending the extra dough to make sure it’s done right.

8. Bad vacuum hose

car vacuum hose

Your car’s gas evaporates over time, slowly wasting your money, but it’s inevitable. When the gas evaporates, it turns into a noxious compounds that are very bad for people to ingest. In response, the government required cars to have Evaporative Emission Control Systems since the 1970s. The system does what it sounds like: helping to prevent pollution. Sometimes the vacuum hoses in the system are damaged and cause the system to fail. This is relatively easy to fix, only requiring new hoses most times, but sometimes it’s hard to tell it’s even happening. If your car smells like toxic fuel, then this might be the problem. You will definitely not pass an emissions test if there is an evap hose leak in your car.

9. Exhaust gas recirculation valve maintenance 

exhaust gas recirculation

Exhaust gas recirculation (EGR) is a system that cuts down the amount of nitrogen oxide that comes out of your car and helps it run more efficiently. It improves efficiency by directing the hot exhaust gases back into the combustion chamber, which warms up the fuel and makes it easier to combust, resulting in higher gas mileage. It also serves the environment well. The failure of this system can cause your car to idle roughly or misfire, because the engine is not circulating the extremely hot air properly. The EGR valve is the most common failure point in this system, which will require you need to replace the valve and clean all the parts, costing just over $300. 

10. Dead battery

car battery

You put a lot of strain on your car’s battery, what with all the accessories you run off it like your phone and those stupid LCD screens you put on the backs of the head rests. Impressively, your 12-volt car battery can handle all of that. Thankfully, though, your car has ways of recharging the battery, with something called the alternator, which converts the mechanical energy created by running the engine into electricity. However, both the alternator and the battery have a finite lifetime. If your battery is just old and bad, and it’s not a fault in your alternator’s charging abilities, a new battery will cost you around $100.