You are driving along, minding your own business, thinking about where you are going, all the things you need to accomplish before the day is over, and then what happens? Your check engine light comes on. Just what you need – one more thing to put on your to do list, and one more expense when there are already too many. Don’t panic! It may not be all bad.
The bad news is, usually when the check engine light comes on, there is no warning. It’s not like your car makes funny noises before it happens, or overheats, or smokes. The light just comes on, period. There is no other explanation. (Did I tell you I had a cousin who just put her chewing gum on her dashboard over the light – not a good idea!)
The good news is that it is not always a catastrophic situation. It might be something as simple as your gas cap is not screwed on correctly .... so, don’t panic!
What you don’t want to do is ignore it. What you do want to find out what is causing the light to come on, which is a really simple thing to do.
The first thing to do is pull to the side of the road and tighten the gas cap. This might be all that is needed, and your check engine light will go off, and you can go on with the rest of your day. If this doesn’t solve the problem though, bring the car in.
In a matter of minutes, we will plug your car in, run a diagnostic and find out the cause. We do this by plugging in a small computer underneath the dashboard and we have the right diagnostic tools to do this no matter what make and model your car is. The computer gives us a code, which tells us what the problem is. (You’d think with all the fancy stuff on cars these days, they could just tell you directly, right?) My guess is that they are afraid to do this in case the code is misinterpreted or whatever.
Here are the five most common causes of the check engine light coming on, none of them catastrophic to your day nor your wallet:
1. Loose or Faulty Gas Cap: I did mention this above, but this could still be the problem. The cap might be cracked. Seems minor right? And it is. Except that a malfunctioning, cracked or loose gas cap mean fuel vapors are escaping and this can actually throw the whole fuel system off. In this case, we will replace the cap, a minor charge, and you are on your way.
2. Worn Out Spark Plugs: The spark plugs seal the combustion chamber in your car and initiates combustion in your engine. When the plugs fail, they misfire. You’ll feel a jump when you accelerate if your plugs are failing. Plugs can last a pretty long time in a car; in newer cars even up to 100,000 miles. When your plugs fail you need to get them replaced right away. This is an easy and inexpensive fix, and your car will run better and not be jerky when you accelerate, so get it done.
3. Bad Mass Airflow Sensor: The mass airflow sensor tells the car's computer to add the proper amount of fuel based on the air coming through to the engine. A faulty one can increase emissions, cause the car to stall, and decrease gas mileage. So, if your car has been stalling before the check engine light came on, this is most likely the problem, although this will not always happen before the check engine light comes on. This failure is also something that is easily avoided if you bring your car in for regular maintenance. The main cause of a bad mass airflow sensor is a dirty air filter, or an air filter that has been installed incorrectly or never replaced. The air filter on your car should be replaced yearly, end of story. And then no problem with the airflow sensor will occur. Replacing the Mass Airflow Sensor can be several hundred dollars – so change your air filter regularly!
4. Bad Oxygen Sensor: An oxygen sensor monitors the amount of unburned oxygen in the exhaust. If the sensor is not functioning properly, it doesn’t provide the right information to the cars computer and ultimately causes a decrease in gas mileage – which is why it’s a good thing that you know this is happening. No need to flush money down the drain by getting lousy gas mileage. Most cars have more than one oxygen sensor and the diagnostic computer will tell us which one needs to be replaced.
It’s also important to replace a faulty oxygen sensor because not replacing one that is faulty can eventually lead to a broken catalytic converter, and this is a very expensive repair. So better a much, much less expensive sensor replacement now, than replacing an expensive catalytic converter later.
5. Bad Catalytic Converter: This is not such good news. You usually will notice something is going wrong with the car before the check engine light comes on in this instance. You will definitely notice a decrease in gas mileage or your car might not even go any faster when you push the gas pedal.
What does a catalytic converter do? It works to reduce exhaust gases. It converts carbon monoxide and other harmful materials into harmless compounds (which is what the State of California loves, right?) So a failed catalytic converter stops converting carbon monoxide into other harmless compounds. Catalytic converters shouldn’t fail if you regularly maintain your car. A failed catalytic converter is caused by other things like a failed oxygen sensor or maybe deteriorated spark plugs.
We can replace the catalytic converter for you if it’s necessary, but it is an expensive replacement. So please, bring your car in for regular maintenance and particularly if you notice a decrease in gas mileage before we have to go to this extreme.
Of course, there are other reasons your check engine light might come on. But these above are the most common. So next time your light comes on, be sure you take care of it right away.
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