Diagnostics is/are not often a “while you wait” process. It takes time to decipher the trouble codes and find the reason the #checkenginelight to be on. Just because you have a code for a O2 sensor lean for example. The sensor has read the exhaust and sent that reading to the #PCM the PCM then makes fuel delivery adjustments to compensate for the cause of the “lean” condition. and turns on the check engine light. For this reason, it’s not just as easy as #changingapart it takes sometimes hours or days to “trackdown” the cause not the symptom. ( The check engine light being a symptom)
