Most Common Check Engine Light Problems

When the check engine light turns on, the driver’s first question is why. The short answer would be to notify the operator a malfunction exists somewhere in the emissions system. The light is highly visible and can be distracting. The manufacturer did this on purpose so car owners would seek out diagnosis instead of continuing to drive with the light on. This article will cover why you should fix the problem and common failures that can illuminate the warning light.

Why Cars Have this Light

The main goal of the check engine light was to protect the environment by notifying drivers their vehicle might be polluting the atmosphere. Malfunctions in the Emission system can cause an imbalance in air fuel mixture and therefore elevate tailpipe emissions. This imbalance is not good for the environment and it is also potentially harmful to certain automotive components. Diagnosing and repairing issues quickly can be cost-effective as it might save expensive parts from being destroyed.

Nuisance Codes and Hard Failures

One of the problems with the check engine light is it comes on to notify the driver of a problem but fails to communicate how serious this problem actually is. Whether the problem is an intermittent nuisance code or a serious hard failure will not be revealed until diagnosis is performed. To make it worse the malfunction indicator lamp will stay on until codes are retrieved and cleared.

As an example of a nuisance code that can often be intermittent I will use the small gas vapor leak code to demonstrate my point. From 1996 through 2006 Edmunds has reported this as the most common code to be stored in the on board computer of tested automobiles. Since 2006 through 2010 the gas vapor codes have slipped to the number two position but remain a common check engine light problem. Some professional mechanics think it slipped to the number two position because they started to desensitize the parameters that will force the code to set.

The government has decided that they want to seal the fuel system and prevent any vapors from entering the atmosphere as they could be harmful to the ozone layer and add to greenhouse gases. Manufacturers have built in several different systems to test the integrity of the fuel system. On many cars when the ignition key is turned on a small pump will pressurize the system. A pressure sensor will monitor the drop over a specific amount of time. Obviously if the fuel cap is loose this system will not hold any pressure. In 1996 a code would set right away. In more modern vehicles it will have to fail several pressure tests before codes set.

There are many other reasons that a vehicle would fail this pressure test even if the fuel cap is secured properly and not leaking. Mechanics consider this a nuisance code because problems in this area will not stop the driver from reaching their intended destination. No one wants to see any harm come to the environment and problems with emissions should still be addressed and repaired promptly.

Serious Check Engine Light Problems

In the Edmunds.com article and also mentioned on the car M.D. site they discussed the top five most common check engine light problems. The most serious and potentially expensive reason a check engine light could be turned on would be a cylinder misfire code. These codes are in the P0 300 range. To be more specific P0300 is for a random misfire. A P0302 would stand for a misfire on cylinder number two. The random misfire can be the hardest to diagnose because it’s not indicating a specific cylinder.

These problems can also be intermittent and therefore hard to chase down. The reason that professional mechanics consider this a serious problem is when a cylinder doesn’t fire raw gas can be discharged from the exhaust valve and make its way down to the catalytic converter. Fuel in the catalytic converter is a bad situation and can damage this expensive component quickly. On more modern vehicles if a misfire is detected on several key cycles they will flash the check engine light instead of illuminating it steady.

This is one situation where the manufacturer makes an attempt to distinguish the difference between a problem and a serious problem by flashing the light. If you read in the owner’s manual what the flashing light means and what is the recommended procedure often the car-maker will recommend that the vehicle be towed to the dealership instead of being driven there. This is to prevent any damage to the catalytic converter and reduce the chance of fire.

When the check engine light comes on it is a message to the driver to seek out service and diagnosis to find out exactly what is wrong. Although we can’t tell you exactly what’s wrong with your automobile in this short article we can tell you what some of the most common check engine light problems are. The good news is the problem could be a simple nuisance code like the vapor described above. The bad news is it could be a more serious issue such as the random misfire that could cause additional damage to other components on the automobile. Drivers are encouraged to seek out diagnosis to find out exactly what is wrong.