The Confusion:

Today's automotive computers will try and compensate whenever there's a problem: so drivers in most cases won't even notice any deterioration in performance. Even though fuel mileage may be suffering and the engine producing high levels of hydrocarbons and other tail pipe pollutants.

 Failure to have it looked at by a professional in a timely manner can lead to other systems malfunctioning and consequently leading to failure and unnecessary repairs. When the computer can no longer compensate and recalibrate for whatever malfunction is occurring, the computer will override the input and go into preset "run on" program allowing the driver to continue to drive and appear that everything is normal except for

the light on the dash.

This is where the confusion really starts, some will tend to ignore the check engine light because they feel no difference in the way the vehicle is running not understanding that a malfunctioning system or component triggered the light and is making other systems work even harder.

Having codes read do not directly tell what's wrong. The only thing a code really indicates is what system or circuit needs to be tested to isolate the actual problem. Each and every code has its own number to match its system and or circuit, sensor(s) or actuators. Every numerical code also has its own test procedure laid out step by step, each step must be performed in absolute sequence skipping steps makes the test useless and leads to miss diagnosed system(s) and hundreds if not thousands of dollars in unnecessary repairs. The testing procedure is the most critical part and can only be done with a scanner or diagnostic computer "code readers" do not have this capability .Tests will include voltage readings, ohm's resistance, and temperature and time values. These tests are very valuable in finding the root cause of failure and should only be done by a competent experienced professional.