Q: EML light on and caution light with arrow around came on the car, what should I do?

The warning lights mean that the vehicle’s computer has detected a fault in the engine management system and/or engine controls which includes a lot of sensors and other devices. If the vehicle has not entered "limp mode" (reduced performance), is NOT actively misfiring, and otherwise appears to be functioning normally (no overheating, stalling, strange noises, etc.), you can usually operate the vehicle safely until your first opportunity to get it diagnosed. Obviously, do not operate the car indefinitely with the EML light on and, in particular, if the car is misfiring do not operate it at all because such will destroy the catalytic converter.

The particular fault, causing the EML to illuminate, would be unknown (there are literally thousands of fault codes in these computerized engine management systems but maybe hundreds are "commonly" experienced) until a Mechanic uses an appropriate scan tool to download and decipher the fault code(s). Once the codes are read, the components, sensors, parts, systems or wiring that are referred to, or identified, in the fault code(s) MUST be individually tested or diagnosed. The key thing to understand is the fault codes DO NOT, and cannot, conclusively identify failed parts, so you should not let anyone replace parts on the basis of fault codes unless and until the part slated for replacement is TESTED to see if there is actually anything wrong with it. So, if you take the car to a garage and they say they are going to replace part "x" because the fault code "says so", ask them if they actually tested the part and further, on the basis of that testing, were they able to reasonably condemn it. And, then, if they do replace a part, be sure you take the old part with you just in case their repair does not resolve the issue (by keeping the old part you obviously preserve the possibility of later testing it yourself, if you end up with a failed diagnostic). The thing to do in a circumstance like this is get a competent diagnosis so that time and money is not wasted randomly changing out parts on the basis of guesses as to why the fault code(s) was set by the computer. If you want a competent, professional Diagnostic which will get to the root issue, feel free to set up a mobile visit with YourMechanic. If you have other technical concerns or questions, by all means feel free to re-contact us. Best wishes with this..if you ask lots of questions you will get the issue identified and resolved to your satisfaction.