The CEL comes on because the on board diagnostics is sensing a problem. There are hundreds of causes for the CEL, some can be totally ignored (in that they won't cause a worse problem); others should be addressed or you could end up stranded roadside. Some, if not addressed will cause lower gas mileage, and soon you'll pay more in gas than the cost of the repair (and still have that annoying light on).
If you pay a mechanic to diagnose and fix the problem, he should reset the CEL.
You could stop by an auto parts store (AutoZone, Kragen) and have them scan the code and reset it. Ask if it's free before they do it.
If like many Subaru owners, you have something other to do on a daily basis than check and reset the CEL, you could buy an OBDII scanner ($50-$150) to (check the code) and reset the light manually. My Forester light comes on about 3 times per year, usually with a new problem that is never less than $250.
In my experience, ultimately, you want to sell the Subaru.
Check this site for information: http://www.troublecodes.net/Subaru/
I would bring it in, because you can never be sure
Belt was probably installed incorrectly. Take it back and have them check it.
Above the gas pedal, under the dash, there is 2 wires with clips that you plug together. Check engine light will flash the codes recorded in the ecu.
You need an OBDII computer a) to read the reason for the check engine light, and b) to reset the error code if you know what caused the light to come on. If you don't fix the condition that caused the light in the first place, it will probably occur again.
your engine is stuffed
yes
A flashing CEL means a serious problem, not just a warning. Get it read asap. You might not even want to drive it there.
With the proper scan tool.
the very top left of the speedometer area.. Mine stays on all the time and still passes emissions. Same year. 200,000 miles and going strong.:)
why the engine light of my subaru came on after i washed the engine
Not necessarily.