2001 Lexus IS300 Q&A

2001 Lexus IS300 Question: Car running great check engine light suddenly came on

I recently had my car in for spark plug changes (first time) the brakes done and ball joints replaced. All regular repairs that have never been done. The car's been running great. tonight the check engine light suddenly came one. 2 weeks ago the headlight balance light came on but is off now. what gives? how worried should I be? I don't feel anything wrong -
Answer 1
SCAN CODES AND POST IT COULD BE A NUMBER OF ISSUES EVEN A GAS CAP -
Comment 1
thank you, I will try the gas cap first and see where to go from there. If it is the cap, how long before the light resets? or will it on its own? -