The engine on my ‘05 VW Passat recently flooded while driving in low area during heavy rain. Had everything fixed and car is running perfectly. Yesterday the check engine light came on but the car seems to be running perfectly. What should I check?
There is a data connector that a tester can be hooked up to that will tell you what needs attention. A VW dealer can do the test at little to no cost; then it's your decision what to do with the info. Don't be pressured into a repair until after you've had a couple of estimates.
The quickest and easiest solution is to have the system scanned by your local mechanic or auto parts store. Here in calif we have stores that will provide this service for free. This will tell you exactly what the problem is and save you a lot of time and guesswork. It can be as simple as a loose gas cap to a computer problem. Since you have no other symtoms than I would go with the scan.
Go to an auto parts store and have it scanned for free. They will tell you what code(s) are present and what they mean. Likely a sensor has gotten wet, tripping the check engine light. It may be able to be dried out with some WD-40, or it may have to be replaced.
