There are ways to troubleshoot a car check engine light that can save time and money. Do it yourself up front to see if you can fix the problem before taking the vehicle to a repair shop.
For a vehicle to pass an emissions test, the check engine light has to be off. If the car check engine light is on, the car will fail that portion of the emissions test. It is also good in general to have a car in good operating order and the check engine light may indicate a serious problem.
If the car failed an emissions test, look at the code or codes provided by the emissions testing facility. Check with an auto parts store for what these codes mean. There is usually several options of what may be the problem.
Begin with the easiest, cheapest fixes first. A check engine light may come on because of a loose hose or seal. Tighten anything that appears to be loose.
Replace the car's air filter to see if that may remedy the problem. Open the compartment and take out the old air filter. Replace it with a new air filter. Securely close the compartment.
Buy a bottle of fuel additive/cleaner and add it to the gas tank. Add gas so the tank is full.
If the above actions did not make the car check engine light go off, review the list of possibilities, such as the oxygen (O2) sensor or MAF (mass air flow) sensor. These may need to be cleaned or replaced.
Go to a repair shop that advertises they check the cause of the check engine light being on for free. There should be no charge for this diagnosis.
