Service Light Diagnostics:

Check Engine or Malfunction indicator light (MIL)

It's what almost every motorist has to go through once in a while: the Check Engine light. If this warning light stays on, it means that your vehicle's computer has detected a problem that can affect your vehicle's fuel economy and emissions. Let's look closer at why the Check Engine light comes on and explore your options on how to deal with it.

First, how it works. Your car has a computer that controls the powertrain (engine and transmission). This computer is called Powertrain Control Module (PCM). It works by monitoring signals from various sensors and adjusting the engine and transmission performance for better fuel economy and lower emissions. This computer has a self-testing capability (called ON-Board Diagnostic or OBD-II). When it detects a fault with one of the systems or sensors, it turns on the Check Engine light on your dash. At the same time, it stores the fault code in its memory. There are a few hundred possible codes.

To diagnose the problem, your mechanic will have to connect our computer to your vehicle and retrieve the code from the computer. The code or codes itself doesn't tell exactly what part is defective, it only tells what system doesn't work properly or what parameter is off. Your mechanic will have to do further testing to find the defective part. Once the problem is repaired, your mechanic will reset the Check Engine light.

Is it safe to drive with the Check engine light on? Is it possible to repair the problem DIY? We will try to answer these and other questions in this article.

What needs to be checked first?

Check if your gas cap is tight

If you check your owner's manual it will probably tell you to check if the gas cap is tight. This is because the Check Engine light may come on if your gas cap is not closed properly. Usually it happens soon after a fill-up at a gas station. If you did find that the gas cap wasn't tight, close it properly and if there are no other problems, the Check Engine light will reset by itself after a day or two of driving. If the gas cap was tight, there is probably some other problem. Please call and make an appointment. 1-360-755-5801.

Is it safe to drive with the "Check Engine" light on?

It really depends on what the problem is. It could be something minor, like a loose connector or low battery voltage, but it also could be a more serious issue that could cause more damage to your vehicle. In worse cases, a car may stall or lose power. We recommend to have your car checked out as soon as possible to be on the safe side. If the Check Engine light is blinking repeatedly, it means that the engine computer has detected that your engine is misfiring, which means that some of the engine cylinders are not working properly. Driving with a misfiring engine could damage your catalytic converter, which is a very expensive part. Check your owner's manual, it will probably suggest to hsave the vehicle towed or at the verry least drive very slow.

Common problems that can cause the Check Engine light to come on

In older cars, it was typically something like a bad oxygen sensor, faulty mass airflow sensor, failed catalytic converter, worn-out spark plugs, ignition wires, a loose gas cap or a clogged-up EGR system. Newer cars have a lot more electronics, which means, many other things could go wrong too. It's practically impossible to find the problem without at least scanning the vehicle and retrieving the stored code(s).

Where to take your car for repairs?

MotorWorks Northwest 1-360-755-5801 we will use a state of the art computer and do the research to determine the cause.

Can overfilling the gas tank cause Check Engine light to come on?

Yes, overfilling the gas tank can trigger the "Check Engine" light to come on. Modern cars are equipped with the Evaporative System that prevents gasoline vapors from escaping into the atmosphere. When we overfill the gas tank, the excess gasoline can enter the part of the Evaporative system called the Charcoal Canister, which is designed to absorb gasoline vapors rather than raw fuel. This can cause some problems with the evaporative system that can trigger the Check Engine light.

Don't overfill the tank past the first click of the pump. Check your owner's manual.

Tips to prevent the Check Engine light from coming on:

• Don't overfill the fuel tank. Fill up till the first click of the pump. Overfilling can cause problems with your vehicle's Evaporative emission control systems (EVAP) resulting in the Check Engine light coming on. After filling up, make sure the gas cap is tight and the gas cap strap does not get caught under the cap.

• Change engine oil regularly. Long intervals between the oil changes do not directly cause the Check Engine light to come on, but many Check-Engine light problems stem from lack of oil changes.

• After checking or replacing the air filter, make sure it's installed properly. If unfiltered air is allowed into the engine it can cause damage to the vehicle's mass airflow (MAF) sensor, which will turn the MIL on. It's best to use only OEM or known good quality air filters.

• Lack of tune-ups is another common reason for the Check Engine light to come on. Old spark plugs, dirty throttle body, bad ignition wires all can cause engine problems with the Check Engine light coming on.

• The corrosion in the wiring and connectors of the car computer system is another major cause of the Check Engine light problems. Your car or truck is full of electronics with wires and connectors located in many places throughout the vehicle, including areas behind the kick panels, under the carpet, in the engine compartment, underneath along the frame, near the gas tank, etc. Anything you can do to keep the electronic modules and wiring free from corrosion will help avoid related problems. For example, if your engine undercover is damaged, it can allow moisture into the engine compartment causing corrosion. Similarly, moisture inside the car can cause corrosion of the wiring under the carpet. Keep the electronics dry.
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