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Eric, Automotive Repair Shop Manager
Category: Mercedes
Satisfied Customers: 31907
Experience:  20+ yrs. experience as repair shop manager and technician.
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I have a 1999 C280 Sedan and my engine light came on and I

Customer Question

I have a 1999 C280 Sedan and my engine light came on and I replaced the gas cap, but the engine light is still on.
Submitted: 1 year ago.
Category: Mercedes
Expert:  Eric replied 1 year ago.


Ok, did you replace the gas cap because the fault code retreived using a diagnostic scan tool showed an evaporative emissions leak, or just because you either read it would solve the problem of the check engine light being on or because you were guessing at the possible issue?

Customer: replied 1 year ago.
I read it might resolve the problem
Customer: replied 1 year ago.
Are we still connected?
Expert:  Eric replied 1 year ago.


Ok, the check engine light only comes on when the onboard computer detects a fault in either the engine management system, transmission, or emission control system. Faults can range from vacuum leak, engine misfire, transmission problem, emission control leak, one of dozens of engine or transmission sensors, or even internal engine or transmission failure. There are over 500 fault codes that can cause the check engine light to come on. And not every one has symptoms you can feel or see or hear.

The only way to determine which of the over 500 faults is responsible is to have the onboard computer read with a diagnostic scanner. once this is done and the fault code retreived then pinpoint diagnosis can be done and repair done.

without knowing which of the over 500 faults is responsible, it is simply impossible, as well as irresponsible for anyone to guess at to which one is responsible for the check light coming on, and as you found out, guessing doesnt work and causes you to spend money replacing a part that is actually good as you did with the fuel cap

Unless you live in California, you can run your car by any major parts store and they will retreive the fault code and definition for you for FREE. At that point, you can decide if this is something you can repair yourself or have a professional do the repair

Customer: replied 1 year ago.
I am better off taking it to my mechanic this was a waste of time and thanks for nothing!!!!!
Expert:  Eric replied 1 year ago.


Sorry that I cannot guess as to which of over 500 fault codes is responsible!!!! Or would you rather waste money replacing parts that likely will not fix the problem by doing guesswork.

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