An alert message come up saying i have Lamp Defective but I cannot find any defective bulb at all. Any idea what's wrong with it?

Check the rear license plate bulbs.

The license plate lights are ok. It is really weird.

Have you checked the bulb in the center brake light? When I had such a message, I checked all the usual suspects, but I forgot about the center brake light--that turned out to be it. Good luck.

Joe B.

On mine it is typically a backup light that is out.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

One way to narrow it down is to pay close attention to what event triggers the lamp out warning.

Start the car, put your foot on the brake, and wait a second. If the warning comes up then it's a brake light.

Turn the parking lights on, one click clockwise on the headlight switch. Wait a second. If the warning comes up then it's a tail or marker light.

Turn the headlights all the way on. If the warning comes up it's a headlamp.

Put the car in reverse. If the warning comes up it's a backup lamp.

- JimY

Inspect the Rear tail light bulb holders..The Plastic housing will Melt and will cause loose contacts and a Bulb Failure Message

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MBENZNL.com

only exterior bulbs tied to the light warning system:

low beam (2)
high beam (2)
fog light (2)
front turn signals (2)
corner lights (front) (2)
rear stop light (2)
rear turn signal (2)
reverse light (2)
rear license (2)
third (aka Dole) brake light (1)

plus (especially) well know weak spot highlighted by Mark:
weak connectors in rear tail assemblies due to poor design

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-- raymond~
47º 34'N 122º 18'W

2001 e320 55k
light defective, check all lights ok, reverse light bulb in trunk
cover rear right side 12v 21 watt a blue socket open trunk, the left side one ea. Back up bulb, the other side left one is fog tail light, pull out light sw on 2 times