Articles

What does it mean when my “check engine light” comes on?

The “check engine” “service engine soon” or little glowing light shaped like the silhouette of an engine is an indication that the engine management system of your vehicle (computer controls) is having either an input that is not functioning correctly or an output device that is not responding as the computer expects it to. These problems may result in an apparent problem with the way the vehicle runs or you may not feel anything. Either type can be serious and should be checked quickly. (more information)

Here are some tips on what to do if the “check engine light” comes on. Remember, the “check engine light” can mean anything from a loose gas cap to a seriously misfiring engine. Ignore the warning, and you could end up damaging expensive components. It also can be a sign that your car is getting poor fuel economy and emitting higher levels of pollutants. You should always have the car checked as soon as possible to prevent expensive damage.

1. First, look for a serious problem that requires immediate attention. Check your dashboard gauges and lights for indications of low oil pressure or overheating. These conditions mean you should pull over and shut off the engine as soon as you can find a safe place to do so.
   
   
2. Reduce speed and load. If the "check engine" light is blinking or you notice any serious performance problems such as a loss of power, reduce your speed and perhaps try to reduce the load on the engine, such as to stop towing a trailer. A blinking light usually indicates a problem that needs immediate attention such as an engine misfire which may be due to unburned fuel passing into the exhaust system, where it can quickly damage the catalytic converter and require an expensive repair.
   
   
3. Contact your Colorado Select NAPA AutoCare Center for assistance, they can get to the root of your problem with the latest diagnostic techniques and state of the art diagnostic equipment. Don’t worry most check engine light problems, if they are fixed quickly, are usually not expensive. 

The best thing about the 'Check Engine' light is that it lets you fix little problems before they become big, expensive problems. And not every problem gives you obvious indications (hard starting, rough running, stalling, etc.) that something is wrong. That's why you can't ignore this important little light. The 'Check Engine' light also alerts you to problems like poor gas mileage or reduced performance. These can evolve so slowly that you get used to them. But your on-board computer is sensitive enough to detect even gradual changes, then let you know when something is wrong.

HISTORY AND BACKGROUND

For decades, cars had dashboard indicators that only monitored the basics: fuel level, oil temperature, coolant temperature and whether the generator or alternator was charging. That all changed in 1981 when federal clean air statutes required catalytic converters to be put on all domestic cars and light trucks to help reduce the level of smog-causing emissions in the atmosphere. Emission control is a process that involves sophisticated sensors that compare the air contents entering and leaving the catalytic converter. Because so many other parts of the engine affect what ultimately comes out of the exhaust, it takes an on board diagnostic (OBD) system to keep everything performing properly.

In 1996, the federal government required U.S. automakers to upgrade to OBD II, a sophisticated system of sensors and actuators that conduct on-the-road diagnostic tests. When the OBD II detects a problem, it logs it as a fault code in the vehicle’s computer memory, and when retrieved via a diagnostic reader this code directs the repair technician to the source of the trouble. Some problems may be major and some not, but because each can affect engine life efficiency and performance, the consumer should investigate them all. The Environmental Protection Agency estimates that more than 6 million Americans are currently driving cars with the “check engine light” on.
 
WHAT THE “CHECK ENGINE LIGHT” MEANS

Exactly what the OBD system looks for depends on the make, model and year. While OBD II set the standard for American-built passenger vehicles, many foreign automakers have added their own proprietary diagnostics. As a result, the “check engine” lights themselves, and more than 100 possible problems they can detect, vary considerably. Under OBD II regulations, the computer system essentially acts like a built-in emissions testing station which monitors and adjusts dozens of components and processes. It continually samples exhaust emissions as they come out of the engine and when they leave the catalytic converter, the device that removes carbon monoxide and hydrocarbon pollutants from the exhaust. The system also monitors the car's fuel system to ensure that gasoline vapors are not escaping into the atmosphere through a leak or a loose or missing gas cap.

Most problems are caused by air/fuel mixture, bad spark plugs or plug wires, or a failed oxygen sensor. Anything that causes poor engine performance or inefficiency, however, could trigger the light, and seemingly unrelated problems with the transmission, anti-lock braking system or even a loose gas cap could also trigger a “check engine light” warning. Though the warning may be caused by something minor, it can also predict a potentially dangerous situation. A thorough engine analysis by an authorized dealer or mechanic is the only safe and reliable way to find out for sure.

On some cars, the “check engine light” may simply go on; on others, it may flash to indicate an immediate, potentially damaging situation. The light may be turned off either by a repair technician, or the OBD II will automatically turn it off when it fails to detect the problem after several diagnostic cycles. You should read your Owner’s Manual to learn what the “check engine” light means on your vehicle.

Fault codes are numeric codes generated by the OBD II system when a problem is detected. When a sensor registers that is beyond the manufacturer’s normal specifications, or an electronic component has failed to respond to a command from the computer, the computer recognizes it as a fault and records a number that identifies that problem. When it finds a problem the computer turns on the warning indicator which may be labeled "check engine," "service engine soon" or "check powertrain," or simply show a picture of an engine, known as the International Check Engine Symbol.