Q: The car needs a jump after sitting for three days, and now the emission light is on.

Hello. The best step to take when any warning light illuminates is to have the vehicle scanned for diagnostic troubleshooting codes. This will tell you what issue the computer has detected within the emissions system. There may have been a moment during the jump starting procedure when the engine received more or less gas than the standard amount.

This may have triggered the warning light that you have received, although there is nothing truly wrong with the vehicle. After enough restarts or miles driven without the issue reoccurring, the light will turn off after passing the test. If the vehicle is running normally, I would not be too concerned yet. Have it scanned and work with the information that is given.

I recommend having a certified mechanic, such as one from YourMechanic, come to your location to determine why the warning light is on and suggest the necessary repairs.