Check Engine Light

Oh, the dreaded malfunction indicator lamp! We’re here to help you through the process

1. Don’t panic. If the light is on solid, and the car seems to drive normally, the problem is usually not an urgent concern. You can schedule a convenient time to bring the car in for evaluation.

2. A loose gas cap or low oil level can cause the check engine light to come on. Be sure to check the motor oil because low oil can cause major engine damage. Check the gas cap also, since there’s reason to pay us to figure out the gas cap is loose. If you find the cap loose, it will take a day or two for the light to go out after you tighten it.

3. If the check engine light is blinking, limit your driving or tow your car.  Further driving may damage the catalytic converter which can cost thousands of dollars to replace.

4. There is only one check engine light but thousands of reasons it could be on. If you drive around with the check engine light on for long time, problems may stack up, making diagnosis and a quick turn-around more difficult.

5. When the check engine light is on, a “trouble code” is stored. This code may be caused by a “hard fault”, meaning the problem that is causing the light is happening right now. It may also be caused by an intermittent fault, meaning the problem occurred in the past but is not occurring now.

6. There are four types of codes: current, pending, history, and permanent. Current means the last time the computer checked, there was a problem. Pending means the computer detected a problem the last time it checked, but it will not turn on the check engine until it sees the problem again. History means the computer has seen a problem, but the last time it checked, there was no problem, so it turned off the light but remembered what happened and stored a code. Permanent codes are only found on newer cars. A permanent code cannot be erased by a mechanic after the repair. The self-test that originally failed and caused the code to set must run and pass before the check engine light will turn off.

7. A trouble code is not a diagnosis. For instance, if a code sets for an oxygen sensor heater, it does NOT mean the oxygen sensor heater is bad. It could be the wires going to the sensor, it could be the driver in the computer, or it could even be there is a flaw in the programming that can be fixed with an update. Some shops offer “free check engine light diagnosis”, when all they’ll really do is check the trouble code. The people responsible for deliberately misleading the public, like Pep Boys and AAMCO should be beaten in the public square. They are pretending to be nice guys to get you in the door, then charging excessively for repairs using low quality parts.

8. The check engine light comes on because one of the computer’s logical tests has failed. These tests are called “monitors”. Some monitors are dependent on other monitors, meaning that some monitors cannot run unless another monitor has run successfully.   This means that if a monitor with dependencies has failed, causing the check engine light to come on, once the problem is fixed, the dependent monitor may run and fail. What does this mean? The check engine may be on, then problem that caused it can be fixed correctly, and then the check engine light may come on again right after the repair (with a different trouble code).

9. Not all warning lights are check engine lights. Some cars like older Nissan vehicles have a “service engine soon” light instead of a check engine light, but most of the time the check engine light light will be yellow with an engine icon with the word “check” under it. It helps to take note of all warning lights and describe them when dropping off the car.