Go to an auto store parts and have the codes read.
When was your timing belt most recently replaced?
Have you kept up with transmission fluid, VTM-4 fluid and oil changes?
Does the car burn or leak any oil?
Have you ever changed your spark plugs or had the valves adjusted?
Nobody can read the car's mind, so get the codes read and you'll have a better idea what could be wrong.
That's a lot of miles so it could be basically anything.
Emissions light is likely P0420 and/or P0430. When an engine is under a load working harder, it's likely the system detected unburned fuel in the exhaust. I'd ask where your at on the maintainace. Start with simple maintanance with one modification, Disable the VCM.
Replace Air Filter
Clean the MAF
Air intake hose air tight
New spark plugs
Inspect spark plugs tubes for oil
Replace PCV valve
Replace EGR valve
Use Full Synthetic oil
Use a Top Tier 87 octane fuel or frequent use of injector Cleaner
245k is nothing to sneeze at. You may need catalytic converters replaced. You may have already done some of these things.
Yes, getting the actual codes would be good.