I believe this means that a disc may be jamming inside the player. I had this happen under warranty and was replaced by my dealer. I will verify in my Mercury Shop manual. Either case, take it to your dealer. You will probably need a new unit.
yes
According to the 1999 Mercury Cougar Owner Guide the six disc CD changer ( if equipped ) is located in the luggage compartment
how do you remove the headliner from a 1999 mercury cougar
No.
Yes , the 1999 Mercury Cougar is FRONT wheel drive
It's a bit buried. Note that the 1999 Mercury Cougar has no user-servicable barts.
Code P1506 - Idle air control valve over speed error
relay R1 is for the fuel pump on a 1999 Mercury Cougar
According to the 1999 Mercury Cougar Owner Guide : ( 58.5 litres / 15.4 U.S. gallons )
The 1999 Mercury Cougar OBD 2 port is under driver side dash left of steering column
I was looking at the 1999 Mercury Cougar Owner Guide and it does not show that it has a gas cap warning light
Ebay, http://www.nextag.com/mercury-cougar-headlights/search-html, or just drive to your ford/mercury dealer.