The rear fog lights are not workin on my peugoet 406

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.

Take out the bulb. Run some fine emery cloth inside the socket and the bulb contacts. Reseat & try it again.

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

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.

REMOVAL & INSTALLATION

See Figures 1, 2, 3 and 4

1. Disconnect the negative battery cable.
2. Remove the fog lamp-to-bumper assembly retaining screws. Be careful not to disturb the adjusting screw.

Fig. Fig. 1: Unfasten the 2 Torx® fog light retaining screws (1), making sure not to disturb the adjusting screw (2)

1. Squeeze the bulb and socket assembly retaining clip prongs inward, and pull the bulb and socket from the rear of the fog lamp.

Fig. Fig. 2: Squeeze the bulb and socket retaining clip prongs inward ...


Fig. Fig. 3: ... then pull the bulb from the rear of the fog lamp

1. Unplug the fog lamp electrical connector.

Fig. Fig. 4: Unfasten the fog lamp electrical connector

1. Install the assembly, retaining bolts and connect the negative battery cable.

AIMING

1. Park the car on a level surface, at least 25 ft. (7.6m) from a wall that is perpendicular to the ground surface. Make sure there is no excess weight in the trunk, unless you normally travel with that amount of weight in the car. Bounce the car a few times to settle the suspension.
2. Measure and record the distance from the ground to the center of each fog light lens.
3. Turn the fog lights on and adjust so the hot-spots (lit area of most concentrated intensity) are 4 in. (10cm) below the height of the lenses. The ADJUSTING screw is located at the top right corner of the fog light.

rear fog light light not working

Check fuse box & bulb for fog lights. If they are ok then check the wiring loom for continuity test & your fog light switch too.
May be it can help you.

Try this, make sure both bulbs are the same. Then try replacing both bulbs.Also go to fuse box usually in vehicle under glove box or steering column and change fuse for those lights.