How do you reset the check engine light on 99 cougar?

To reset the check engine light on a 1999 Mercury Cougar, you can disconnect the battery by removing the negative terminal for about 15-30 minutes. This will clear the engine control module's memory and reset the light. Alternatively, using an OBD-II scanner to clear the trouble codes will also turn off the check engine light. However, if the underlying issue isn't resolved, the light may come back on.