Check Engine Lights

Check engine lights can be a real nuisance and sometimes frustrating to get repaired. In this article I am going to explain what a Check Engine light is, what causes it to come on and the process to repair the issue.

What is a check engine light and what does it do? The check engine light is a warning that something is not right. The vehicles modules monitor every sensor on the vehicle. If one of them goes outside of the preset parameter set by the manufacturer it will trigger a fault code to be set. Not all fault codes will cause a light to illuminate so it is important to have the vehicle scanned periodically to see if any codes are stored in the modules. Once this this light comes on it will stay on until the issue is repaired and the fault is cleared. If the vehicle is driven a certain number of times without the fault being present it will also cause the light to turn off. This does not mean the problem has been fixed and a fault code will Still be stored in the module.

Diagnosis and testing- some parts suppliers now offer “Free Scanning” in an attempt to sell more parts. Well if it’s free what the issue? The issue is fault codes alone do not tell you what the issue is. For instance, let’s say you have it scanned and it has a fault for “bank 2 oxygen sensor too lean”. At that point most places will recommend replacing the oxygen sensor to remedy the issue. The problem with that is simple. A code stating that a certain bank is lean could be numerous things. It could be a faulty Mass Airflow Meter, a vacuum leak, low fuel pressure or volume or numerous other things. This is why testing is so important. The fault code merely gives you a starting point for testing, it is not intended to diagnose a problem.

Another thing to take into consideration is maintenance. Why is this so important? Skipping out on maintenance and repairs can make the repair process more difficult. If there are multiple issues the technician may have to make repairs before proceeding with the diagnosis. This can be confusing to some people who only want the problem they requested to be taken care of. If a repair in the same system of the fault is needed to continue with the diagnostic process then the technician cannot go any further until it is resolved. So be sure to keep all maintenance up to date and take care of repairs when they arise.

Finally the aftermath. It is not uncommon with vehicles that have higher mileage to have problems in the near future after a repair. This means your check engine light may have come on 3 months ago and was repaired but now has come on for a different reason. There are hundreds of reasons why a check engine light can come on so never assume it is the same issue. Be sure that your shop documents the fault codes and gives you a copy for your records.


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