The fog light at the rear is not working. Fuse under dashboard seems to be OK. The bulb works. The other lights work in different modes. The button to switch it on lights up when pressing it. Where do I look?. I have an electrical tester Thanks

check fuse--relay--switch-bulbs==use a meter to test switch connectors--wiring--sockets

First check the bulbs. Both fog lights are usually on the same fuse. The fuse box is under the dash, at knee height on the drivers side. the panel usually pulls loose at the top and hinges down. The Fog lights are Fuse 12 at 5 Amp.
*Note* Only replace fuses with the same colour and Amp rating.

check for more fuses under the hood

Try and see what happens when you put it in REVERSE? There are many American Vehicles that the light only works when you are in Reverse to see what is behind you

try changing the relay for the front fogs,the front and rear are not connected in any way,check the fuse box lid for relay location ok

there is a relay for them.are you sure is not bulb.

I guess that your refering to the backup lights? They have their own fuse and aren't imune to having the bulbs burnt out. The bulbs are easiest to check as they may be black in color or knocked out of their holders. The back up light switch is part of the neutral start switch and they will have other problems like no start if it's bad. wiring and their plugs are also possible mainly if the car as been in an accident or other bending action.

rear fog light light not working

if the fuse on the driver side panel is good,and the relay under the dash is good then check your connections or your bulbs

Check the fuses under the steering column, in the glove box or under the hood by the battery. There should be at least 2 fuse/relay blocks that will have a spot for fog lights