I have been getting a rough idle from time to time that goes away upon restart. This morning I got the rough idle, it went away but my TCS/slip light came on and service engine as well. I pulled the code and got 0201-Primary Ignition Circuit. I'm guessing it's a bad coil. Can any one tell me how to test individual coils or direct me to a thread that does. Can't seem to find anything,and I would rather not change em all!