5 Common Causes for that Annoying “Check Engine” Light

IMG958538by Guest Blogger, Rob Pinkham

The “Check Engine” light comes on in your car:
What do you do?

Understanding what this light is indicating can, in most cases, avoid an over-reaction which often results in an anxious driving experience. The main function of this sometimes annoying light is to warn you that there is an emission related malfunction occurring with the engine.  The 5 most common causes for your check engine light to come on are:

1.   Your gas cap is loose, damaged or missingNot a reason to stop driving the car.  At your next stop, properly secure the cap. It may also need to be replaced as it is not sealing.

2.    Your Oxygen (O2) Sensor needs replacingNot a reason to stop driving the car.   However, over time it may need to be replaced, and you can experience a loss in fuel economy. In some cases this can escalate to a damaged catalytic converter, which is a major expense.

3.    Your Mass Airflow Sensor needs replacingNot a reason to stop driving the car.  Faulty sensors can eventually cause fouled spark plugs and damage the O2 sensors or catalytic converter, resulting in reduced performance and fuel economy.

4.    Your Catalytic Converter needs replacing–  If you notice a rotten egg smell from the exhaust, have it checked.  Get this evaluated by a competent muffler shop. They are best able to determine if it is clogged up or can become a serious hazard from overheating. There will be reduced performance and fuel economy, and your vehicle may run hotter.

5.    Your Spark Plugs or Plug Wires need replacing- Not a reason to stop driving the car.  If not replaced, you will experience poor performance (reduced power, engine missing) and reduced fuel economy.

Most vehicles today employ something referred to as “Limp Home Mode” which are a preset number of parameters established by the on-board engine computer so that the car can be driven home or to a shop without causing engine damage.

It is also important to know what the Check Engine light is
NOT telling you.

1. It is not reporting low oil pressure– you have a separate light or gauge for that.

2.  It is not telling you the engine is overheated– you have a separate gauge or warning light for that.

These are the two main things to be concerned about in relation to damaging the engine as a result of continuing to drive.  If one of these two warning lights come on, you should stop driving the vehicle immediately and call a tow truck.   Choosing to drive on, know your decision may cause a significant repair bill.

As a general rule, when the Check Engine light comes on you can continue to drive the vehicle. There is no immediate need to call the tow truck.  However, making a prudent stop at your local parts store to get a free diagnostic evaluation is always recommended.  With a little common sense you can avoid a major car repair expense.

Rob Pinkham is a graduate of Oregon Institute of Technology, specializing in automotive tune-ups, carburetion and electrical for high performance engines. Over his 40+ years in professional auto maintenance and repair, he has built and operated his own auto repair business, with a particular emphasis on Honda products.