After 20 years just discovered I need a new tail light bulb (allegedly the same as a brake light bulb). I removed the old expired bulb which clearly was marked "921". My only spare from my bulb cabinet did not light up. I queried several auto parts retailers and they claim the application is a 7443 for both. The base on the 7443 bulb is too large for the socket. Tomorrow I will see if I can buy a new 921, but I will use the volt/ohm meter to make sure I'm getting power back there. I can't believe this. I thought all these parts sources cannot be wrong. If I have power at the socket. I will gamble on another 921 and hope for the best. Anyone have an answer???

 

921 are the reverse lights, 7443 are the tail/brake lights, bau15s is the turn signals

 

Thank you.... and sorry. My orientation became confused so after walking away and coming back to the problem I discovered I had lost sight of the tail light bulb partly concealed by the trim. I did learn a valuable lesson. The factory shop manual advises that the rear seatbacks should be removed in order to remove all the trunk trim. Unless your hands are very large you can sneak past the trunk trim by removing two of the screw in "knob" fasteners on the side you are attempting to access, and two pop-it screws located at the rear center of the trunk.