Poor fuel or water in the fuel. Using the wrong octane fuel.For the 2001 you should use Unleaded fuel only.87 to 91 octane.
On a 2000 Mercury Cougar : That's your Anti-theft system status light
I was looking at the 1999 Mercury Cougar Owner Guide and it does not show that it has a gas cap warning light
it is in the manual says when this happens it is 02 sensor and if it is flashing you have a miss in your engine which can cause damage.
You need an oil change.
You are low on coolant.
it is located on the light a switch that says 12sec on and off
Blown fuse
its below freezing temperature
I have a instrument light that is on ---- 1999 Cougar , it looks light a transmission, but I think it is the emission indicator on the far left of the steering wheel, what does this mean?
Check and fix the engine.
The radiator fluid is low or you parked the car at am angle.
On a 2000 Mercury Cougar : The warning light that looks like a can with an X through it , located between the engine coolant temperature gauge and the tachometer ( at the bottom of the gauge cluster ) is your ( LOW engine cooling system warning light )