tail lights not working but brake lights are

Your brake lights work but the tail lights don’t—classic “I’m visible only when stopping” trick.

Likely culprits, in order of how often they ruin weekends:

• Blown tail/park light fuse (separate from the brake light fuse).
• Dead tail light bulbs or dual-filament bulbs with the tail filament gone.
• Corroded sockets or dodgy earth/ground at the tail lamp cluster.
• Faulty headlight/park-light switch or relay.
• Aftermarket trailer plug or wiring tapping the park circuit and shorting.
• Broken wiring in the tailgate or behind trim.

Start with the easy wins: swap bulbs, check the fuse, clean contacts, and test for 12 V at the socket with parks on; if brakes power the brighter filament, wiring to the tail circuit is at fault.

If both sides are out, think fuse/switch; if one side, think bulb/socket/ground. When in doubt, a sparky can diagnose it faster than you can find the torch.