Mill Valley Auto Service knows that the check engine light is one of the most misunderstood warning lamps on all vehicles since about 1996! Worse yet, you may find that some businesses in Mill Valley will plug into your vehicle, see what codes it is displaying and sell you parts that may not fix your vehicle based on those codes adding to the confusion about the check engine light.
As mentioned before, the check engine light is an indicator that lets you know that something is not quite right. When the tech gets a code, that code just tells the tech what sensor or system is not working correctly. So, if a code for an oxygen sensor is generated, it is telling the tech that the sensor is not operating properly, or the sensor is sending a signal that that is out of specification. It is not necessarily telling you that the sensor has actually failed. At this point a Mill Valley Auto Service technician will look up and perform a number of tests and readings to eliminate other possible causes for the code. When the testing is completed properly, the tech will have identified the actual failure which may not be the sensor at all.
In this case, if the cause is not the sensor, and the oxygen sensor is replaced, after a few miles of driving the check engine light will go on again and the same code will appear because the actual issue has not been fixed. This is why replacing parts just because the code points to them usually does not fix the issue.
Mill Valley Auto Service is one of the top shops in Mill Valley because our technicians will read the vehicle codes and use them to look for TSBs or other issues that your vehicle may have commonly. Next, our technician will perform a series of “pinpoint tests” as directed by the manufacturer of your ride. These tests may be electrical, or engine mechanical based on the pinpoint tests that are given. Once the cause of the check engine light is determined, we will contact you with an estimate of what it will take to repair your vehicle.
Upon authorization from you, we will repair or replace the part in question and rerun our code testing procedure after a road test to confirm that the diagnosis was correct, and that the replacement of the part fixed the issue. Note, occasionally there maybe more diagnosis required after the replacement of the initial part due to another failure in the system that the first may have overshadowed.