When the check engine light comes on what do you do! The answer depends on several factors: firstly, is the light flashing? Secondly, is your vehicle running any differently? Thirdly, did you recently fill your tank with gas? What does number three have to do with anything? One of the most common codes tripped by the diagnostic system and stored in the onboard computer is “small evaporation leak.” This code is commonly caused by an improper gas cap seal or a broken gas cap. Therefore, tightening the gas cap will make the check engine light go out if this was the reason for the code.  

Check Engine Light is Flashing 

When the check engine light is flashing it is a sign of a significant issue. The flashing light is to gain your attention. Do not ignore this warning. The onboard computer is letting you know that something serious is wrong with the vehicle. Sometimes this will cause loss of power, known as “Limp Mode.” Limp mode is your vehicle protecting itself from severe damage. When this happens do not push your vehicle. If you are towing something, unhitch and slowly proceed to your mechanic or call a tow truck. It would be highly recommended to call the tow truck as any strain on the engine could cause more damage.  

Issues that cause a flashing check engine light range from transmission issues to catalytic converter problems or failure. The most severe issue would be a total engine failure. Each issue puts you and your vehicle in danger, if you ignore the flashing red light on the dashboard. Therefore, in the case of a flashing check engine light, call the garage immediately. A certified mechanic can diagnose the problem with his OBDII scan tool. OBD stands for on board diagnostics tool, it communicates with your onboard computer where the codes have been stored.  

There are many handheld OBDII tools available for personal use. A certified mechanic has thousands of dollars of diagnostic equipment plus their years of experience to assist them. Therefore, they are the best option for a flashing check engine light.  

NOTE: If the check engine light is normally yellow but now is orange or red. The red is the same as a flashing check engine light. Not all vehicles display the same symbol. It is best to know by checking the owner’s manual for the current vehicle.  

Is The Vehicle Running Differently 

Is the vehicle running any differently? If the answer is no, set up an appointment to have the vehicle diagnosed. The mechanic will attach the code reader to the onboard computer via a port under the dashboard and retrieve the codes. Some of the most common codes are O2 sensor failure, Large Evap leak, misfires and MAF air flow sensor failure. Oftentimes the evaporation leaks will require a “smoke test” which is simply a smoke machine attached to the evaporator system and smoke blown through the tubes and connectors. Smoke will escape through any breaches in the system, alerting the mechanic to the precise location of the problem. Replacing the worn or broken parts will save money in fuel costs and help fix any performance problems.  

If the answer is yes to the question, is the vehicle running any differently. Do not wait, call your mechanic immediately. This issue is more serious than a weak sensor or random misfires. It could be failed coils, wires, a transmission speed sensor or a MAF mass air flow sensor. A failed MAF sensor will dramatically influence performance and can cause more damage if not replaced.  

Four Common Issues Explained 

Four common components that cause most of the codes in a system are MAF sensor, O2 sensor, coil/wires and Evap system. Oftentimes codes are not singular but have two or more that surround a component. This is where the knowledge a certified mechanic has, comes in handy. Knowing how an engine works with all the components helps narrow the issue down for the mechanic. If the code is a singular code than more than likely that specified component has failed.

Mass Airflow Sensor

Mass Airflow Sensor (MAF) sits on the top of your engine between the air filter and the intake manifold. It measures the air flow going into the engine, relaying this information to the on-board computer (ECM) which in turns delivers the correct amount of fuel to the engine for peak performance. The ECM will also use the MAF readings to determine when the transmission shifts. If the MAF is not working properly it may cause the transmission to shift differently. MAF sensors can be contaminated with debris, water, or even packed with snow during a storm. Cleaning the MAF sensor is a delicate task and should only be done by a mechanic. The components are delicate. When the MAF sensor fails the engine might not start or start and instantly stall. Another issue will be poor acceleration and odd shifting patterns for the transmission.  

Oxygen Sensor aka O2 Sensor 

O2 sensors measure the amount of oxygen that is unburned in the exhaust/emissions system. They survive in temperatures over 800 degrees and tend to fail, on average, around 50,000 miles of use. Most newer cars have 4 oxygen sensors. They work together to monitor the emissions system for issues that will affect performance and emissions. If you need to pass an emissions test for inspection and your oxygen sensors are not working properly you will fail the inspection. Non-working sensors will cause increased emissions and lower performance in an engine.  

Miss Fire Issue 

Coil and wires are a common reason for a misfire code. Once these systems are compromised the only solution is to replace them. Misfiring can cause damage to the engine oftentimes catastrophic, if left unchecked. A misfire is when the fuel in a cylinder is left unburned or partially burnt. This will cause a hesitation in the running of the engine. There are other components in the system that can cause a misfire so it is best to have a mechanic diagnose the problem.

EVAP Leaks Large and Small 

The EVAP system, or evaporation system, is the emissions control system. The EVAP system is a sealed system of lines, valves, connectors, and a gas cap. This system recirculates the gasoline vapors in the system thus preventing them from escaping into the atmosphere. When something goes wrong in the system it is categorized as a small or large EVAP leak. A sizable percentage of small EVAP leaks can be the result of a poorly seated gas cap. If removing the gas cap and installing it correctly does not fix the check engine light it could mean any one of the many parts of this system have failed. This will require a smoke test to determine which part or parts need to be replaced. If these parts are not replaced expect to lose fuel via evaporation and a constant check engine light on the dashboard.  

Whether it is a common check engine light issue or a severe issue never ignore a check engine light on the dashboard. A check engine light is the vehicles computer or monitoring system alerting that something is not right. Taking care of a little issue now could save the engine from catastrophic failure. In other words, when the check engine light comes on call a garage and make an appointment for a proper diagnostic before it is too late and the engine is ruined. Having peace of mind is worth the trip to the mechanic.