I have a 2001 Mercury Grand Marquis. The check engine light came on and AutoZone diagnosed it as a misfire on Cyl. #4. I changed all the plugs but I do not know how to turn off the light to see if I fixed the problem. Please tell me how to turn the light off.
You will probably have to change the COP on the #4 cylinder…(COP = coil). Then disconnect the battery for a minute or two…
Did you wash the engine? That’s a big No-no on these engines…
Disconnect the battery for a while.
Or keep driving. If the error condition has cleared by your replacement than the light will go off. Usually its 4 full on/off cycles driving maybe 10-15mins to full temp. However it varies across makes.