Connect an OBD code scanner. The light indicates that the computer has stored a "code", meaning that it has detected a fault in one or more components.
I have just had mine done at the weekend, the gearbox needs to come off along with the driveshaft and various other bits and bobs that get in the way, took about 5 hours in all.
Have it checked for codes, That is the same as the check engine light.
can't be done without dropping subframe
That will depend on what damage was done. A good mechanic can tell you whether it is safe to start or needs to be towed.
Most likely needs a tuneup done. Check the timing and change the normal tuneup part.
You can either get under the dash and disconnect it, put a piece of tape over it if it bothers you or you can buy and engine analyser for about $69. Most of these have a button on them to shut off the check engine light. If the reason your light is on is because of a service that needs to be done and you did it yourself instead of paying a dealer, it will stay off. If there is actually something wrong, it will come back on when you restart your engine.
The cost can range from about $500 to over $2000, depending on what exactly needs to be done. If your car is old, you may do better just trding it in. But ask your mechanic first to see what needs to be done.
A check engine light comes on for a reason. The engine computer has detected something wrong somewhere in the engine management system and your car's computer needs to be scanned for fault codes to determine the source of the problem. If you have done all that then your cars check engine light needs to be reset, how this is done I am unsure. Get the engine serviced! The dealership can provide the service and cancel the alert.
needs to be done with a diagnostics machine.
yes they but it on a scan tool and they should tell you what the problem is and what needs to be done.
A transmission transfers power from the engine to the wheels. If your transmission needs to be repaired, you need to have this done in order to drive your car.
There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.