Check Engine light | Malfunction Indicator lamp| (MIL)

When your check engine light comes on you can rest assured that Shadetree Automotive has the experience, training, and state of the art testing equipment to properly diagnose your check engine light. In many cases it can come on for a very simple thing, in others it can indicate a more complex issue, that may require special testing. Any parts store can pull codes using a scan tool, however part stores don’t have the special equipment or knowledge necessary to always diagnose the problem correctly. We are here to help, regardless if the issue is a simple problem that can be figured out by just reading fault codes or if you need more complex testing, we can help.

  My check engine light is on, what should I do, and can I drive my car?

A check engine light is a warning management system. Its purpose is to inform the driver that the vehicle needs some attention. When illuminated, it is typically either an amber or red color. On most vehicles, the light has two stages: steady (indicating a minor fault such as a loose gas cap or failing sensor) and flashing (indicating a severe fault, that could potentially damage the catalytic converter). When the indicator is lit, the engine control unit stores a fault code related to the malfunction, which can be retrieved with a scan tool and used for further diagnosis. Once the fault code is retrieved with the scan tool, it points the diagnostic technician to the area with the problem. The fault code usually has multiple possibilities, and requires additional testing to determine the exact problem. In some cases, (however rare) the fault code will read the exact problem.

  So first thing first: Check to make sure your gas cap is on and give it a few more clicks to tighten it up. If that does not take care of the problem, take note to how the car is running.

Check your vehicle for the fowling conditions using this check list.

ü  How does the engine sound?  If it makes any unusual sound, you should call Shadetree before you drive it.

ü  How does the engine start? If it is hard to start or cranks for an extended period, you may want to call Shadetree before you drive it.

ü  How does the engine run? Check to see if the engine runs funny. If the engine runs rough at idle, or when on the gas, or has a loss of power. You may want to call Shadetree before you drive it.

ü  Is the check engine light flashing? If the light is on and flashing, call Shadetree before driving. This may require your car to be towed to the shop.

ü  Is the oil or low oil symbol on? If this warning light is on, you should not drive your car. Call Shadetree before driving.

ü  Is there any other warning lights on? Sometimes you can have a low battery light or some other kind of indictor, with your check engine light. If any other light is present you should call Shadetree before driving car.

After you have completed this check list and everything checks ok. It’s most likely you have a minor problem and it is ok to drive your car. You should have your car tested at Shadetree at your earliest convince. Otherwise if you notice any of the symptoms of the above check list, call Shadetree before you drive your car.

Many check engine light repairs are inexpensive to fix. While others are more expensive, it's still important to get them taken care of. Even though the car could be driving just fine, you may be wasting fuel, putting out more pollution and damaging the engine. In Utah you may fail your annual emissions test if the light is on -- especially if the vehicle is a 1996 or newer -- so that's another good incentive to get it checked out.

Whatever you do, don't just slap a piece of black electrical tape over it and go about your business. Cars just need a little love from time to time to stay in good shape, and neglecting a minor issue could lead to bigger problems down the road.


False triggering

False check engine light triggering is rare, however sometimes your computer system might have had some kind of glitch or just needs to be reset. Also higher amounts of methanol/ethanol (or other additives) than the engine is equipped to handle may trigger the MIL. These burn differently from gasoline and the EFI system may mistakenly interpret the oxygen sensor's readings as being incorrect.


5 Common causes of check engine lights

  1-    Oxygen Sensor

An oxygen sensor is a part that monitors the unburned oxygen from the exhaust. It helps monitor how much fuel is burned. A faulty sensor means it's not providing the right data to the computer and causes a decrease in gas mileage. Most cars have between two and four oxygen sensors.

What causes it: Over time, the sensor gets covered in oil ash and it reduces the sensors ability to change the oxygen and fuel mixture. A faulty sensor not only reduces gas mileage, it also increases emissions.

What you should do: Not replacing a broken oxygen sensor can eventually lead to a busted catalytic convertor which can cost upwards of $2,000. Most O2 sensors will cost around $200 depending on the car.

  2-Loose or Faulty Gas Cap

Sometimes a very simple part causes your check engine light. When it's loose or cracked, fuel vapors leak out and can throw the whole fuel system off. This causes a reduction in gas mileage and increases emissions.

What causes it: If you get an error pointing to the gas cap it means fuel vapors could be leaking out of your cap. This means the cap is either cracked or just wasn't tightened well enough. In some cases you may have a cracked fuel line or faulty valve that will cause this code that requires additional tests, to determine the exact cause of this leak. This fault is generally referred to as an EVAP system leak.

What you should do: If your car isn't feeling jerky or strange when the check engine light comes on the first you should check is the gas cap. Pull over, retighten it, and take a look at the cap to see if it has any cracks in it. Continue driving and see if the check engine light turns off. While not car-threatening, it's good to take care of this right away to insure you don’t have any other problems with the car.

  3-Catalytic Convertor

The catalytic convertor works to reduce exhaust gases. It converts carbon monoxide and other harmful materials into harmless compounds.

What causes it: Catalytic convertors shouldn't fail if you're keeping up on regular maintenance. The main cause of failure is related to other items on this list, including a broken oxygen sensor or deteriorated spark plugs. When it fails, it stops converting carbon monoxide into less harmful emissions.

What you should do: If your catalytic convertor fails completely, you eventually won't be able to keep the car running. Your gas mileage will also be terrible, so you should try and fix it as soon as you can.

  4- Mass Air Flow 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.

What causes it: Most mass airflow sensors fail because of an improperly installed (or never replaced) air filter. You should replace the air filter at least once a year to help prevent the airflow sensor from failing.

What you should do: You will notice a decrease in gas mileage and over time the car will eventually start stalling a lot. We recommend replacement ASAP to avoid harmful build up on your spark plugs or fuel system.

  5-Spark Plugs and Wires

The spark plug initiates combustion in your engine. When the plugs are failing, the spark plugs misfire. You'll feel a little jolt in your car's acceleration and or a rough idle when this happens.

What causes it: Most spark plugs in cars from before 1996 should be replaced every 25,000-30,000 miles. Newer ones can last up to 100,000 miles. Sometimes spark plugs can fail do to a faulty sensor or other condition that causes the spark plugs to foul out.

What you should do: Get them replaced right away. Your car will run better for it. Also this is part of your vehicles regular maintenance, the spark plugs should be replaced according to the vehicle manufactures recommendation or when they are not working correctly.