The Top 10 reasons why your “Check Engine” light may go on
The “Check Engine” light is the little glowing indicator on your dash tells you something is wrong with your car. If you drive an older car, chances are pretty good that you’ve seen your Check Engine light on. In fact, a recent CarMD survey suggests that roughly 10 percent of all vehicles on the road have their check engine light on right now. But what causes that light to turn on? Based on an analysis of 160,000 repairs by CarMD, here are the top 10 reasons a check engine light can turn on.
1) Faulty oxygen sensor: O2 sensors measures the amount of oxygen in a car’s exhaust to help the car’s computer inject the appropriate amount of fuel into the engine. A failed sensor can throw off a vehicle’s mpg by as much as 40 percent. O2 sensors commonly fail in vehicles with high mileage.
2) Loose gas cap: Gas will evaporate around the opening of a loose gas cap. There are sensors in the gas system that look for vapor leaks such as this and will trigger the check engine light when they are found. At least this one is simple. If your check engine light comes on, the first thing to do is check to see if your gas cap has been tightened.
3) Faulty catalytic converter: Generally the catalytic converter fails only after something else goes bad and the engine’s exhaust becomes laded with oil or raw gas. Think bad piston rings or a malfunctioning ignition system.
4) Faulty ignition coil: No coil means no spark, and internal combustion engines need spark to run. The coil can go bad by operating under high temperatures or just by getting old.
5) Bad spark plug(s): If your car isn’t firing on all cylinders, you probably have a bad spark plug or two and this means you’re wasting gas. This symptom often occurs because of bad spark plug wires too.
6) Bad mass air flow sensor: This is the sensor that meters the engine’s incoming air and determines how much fuel to inject. If it goes bad, your car’s fuel efficiency can drop up to 25 percent. Fortunately mass air flow sensors are relatively easy to replace and not terribly expensive.
7) Non-compatible aftermarket alarm: Certain aftermarket parts work better than others — make sure aftermarket alarms are compatible and are installed by a qualified technician. If you have an alarm installed on your car and the check engine light comes on right afterward, have the alarm installation guy look at the problem.
8) Leaky vacuum hoses on EVAP system: Loose hoses mean evaporating fuel will not reach its vented destination. This often triggers your check engine light. This is not uncommon on older vehicles because rubber hoses designed to vent gas fumes deteriorate and need replacement.
9) Faulty exhaust gas recirculation valve (EGR): The EGR is an emission control system that pushes exhaust back into the combustion process and helps lower a vehicle’s emissions. A bad EGR valve or blocked system may cause your vehicle to run with a rough idle and engine hesitation, and the check engine light may be triggered.
10) Repair/replace battery charging system: More sophisticated monitoring systems have made batteries and their systems more likely to turn on the check engine light. Batteries are vulnerable to heat and rough use and before they fail, the check engine light may illuminate.
Source: Thompson Chrysler Dodge Jeep Ram