During our previous post regarding the maintenance for your car, one of the readers contacted us and says that he is confused with the car engine lights that trigger signal. Now, I want you to imagine the following situations.

You get into your vehicle ready to run some errands or head off to work. But, as you start it up, you glance down at the instrument cluster and get a shock. The “check engine” light has come on to alert you of a problem.

The check engine light is part of your vehicle’s onboard diagnostic system, which monitors the engine through various sensors. The main task of this system is to find out if there is a problem concerning emissions. If the system detects an issue, it will illuminate the check engine light, a sure sign that it’s time to take it to your mechanic. While a good idea, in theory, the check engine light is one of the most confusing parts of a vehicle.

Check engine light on on a speed gauge of a modern vehicle

The biggest issue is that the light doesn’t tell you what the problem is, just that there is one. To find out, you’ll need to have a mechanic scan the vehicle to get the code that signifies the issue. You can also figure out why the light is on by purchasing a code scanner. This device plugs into the vehicle’s onboard diagnostics system (OBDII) port and pulls the error codes from the system. Depending on the scanner, it can either give you the error code or the scanner will decipher the code and tell you what the problem is.

The other big issue is the mixed signals a check engine light can show. Depending on the problem, the engine light could either stay on or flash. If it stays on, you should consider getting it to the nearest repair shop. If the check engine light flashes, that means there is a serious issue and you need to get it over to your mechanic as soon as possible.

To help you better understand the check engine light, we’ll be running down the some of the common issues that trigger it.


thermostatA vehicle’s thermostat works in the same way as the thermostat in your house. It monitors the temperature of the engine and will either warm up or cool down if it detects a change in the ambient temperature. In the case of a vehicle’s thermostat, the way it varies temperature is by regulating the flow of coolant into the engine. But how can a thermostat cause the check engine light to come on?

One of the leading causes comes down to not changing your coolant regularly. Over time, coolant will gather up bits of dirt and other containments which will stop it from doing its job. The coolant passes over the thermostat and, if not changed regularly, will cause premature corrosion and ultimately cause your engine to overheat.

Gas Cap

There are many reasons why the check engine light could come on. We’ll start with the simplest issue, the gas cap. If you notice that your check engine light is on, you should first if the cap is fully tightened or has been lost. If not, the cap may somehow be damaged. The gas cap may seem like inconsequential part of a vehicle, but it plays a key role in the fuel system.
gas cap
The cap seals the fuel tank and keeps gas from evaporating. If your check engine light comes on, this should be the first place to investigate.

Oxygen (O2) Sensors

Ask any mechanic what the most common reason for a check engine light to come on, and nine times out of ten they’ll say that it is the oxygen (O2) sensor. The O2 sensor plays a key part in the combustion cycle; it measures the amount of unburned oxygen exiting the exhaust. The sensor reports back to the engine computer whether or not it needs to adjust the amount of fuel to help make the engine run as efficiently as possible. If your O2 sensor is malfunctioning, your engine will not operate at its full potential and your fuel economy will drop significantly.

Spark Plugs/Spark Plug Wires

Spark plugs and spark plug wires are some of the most important parts of your engine. Spark plugs help ignite the air and fuel mixture in the combustion chamber of the engine, and the wires deliver the spark from the ignition coil to the plugs. These parts will fail over time due to the high temperatures under the hood and will cause your engine to run poorly. If you don’t change the spark plugs and wires, parts such as the catalytic converter and O2 sensors will begin to fail.

Catalytic Converter

Speaking of, a catalytic converter plays a very special role in your vehicle. This part converts carbon monoxide into carbon dioxide in an effort to reduce the number of emissions being emitted. The converter can be damaged if regular maintenance is not performed on the vehicle.

Regular maintenance in this sense includes replacing spark plugs and O2 sensors. If the converter is damaged, this can present some big problems. First, the engine will not perform at its full potential, and second, your vehicle will not be able to pass a state inspection as it will emit more emissions than is legally allowed.

EVAP Purge Control Valve

The evaporative emissions (EVAP) purge control valve performs an important task when it comes to controlling your vehicle’s emissions. This device allows fuel vapours that have been caught in a charcoal canister to leave and burn off in the engine, instead of escaping into the atmosphere as pollutants. The check engine light will come on if the system detects the valve is stuck open and letting the vapours escape.


car-mechanicAt Car Source, we have done our check thoroughly to ensure that all the cars sold from us are in good conditions. Browse our car collections today or contact us for any enquiries.