Exterior Lamp Failure light
 

1994 E-320 sedan. The "Exterior Lamp Failure" light on my instrument panel comes on every time I put the car in to gear and stays on. I have checked all my exterior lamps and fuses and they are all good.

Any ideas as to what could be causing this anomaly?

Not using German bulbs. Seriously.

If you haven't changed anything and this has been a recent occurrence, you need to trace the steps taken.

Turn off car and restart to reset the lamp indicator.

Tap on brakes without putting car in gear. If light doesn't come on, that rules out brakes, otherwise, check taillights AND rear window brake light .

Put car in reverse. If light comes on, check reverse taillights. Otherwise, move on.

Turn on headlights. If light comes on, it could be one of several bulbs...headlights, front and rear side markers, taillights AND most missed, license plate lights (which set off mine just a week ago).

Good luck.

If lights all appear to be working after performing the above steps, then I would move on to another issue I dealt with many years ago. The metal rails in the taillight housings sometimes loosen over time through vibration and throw off the ground leads to the bulbs, sending a false signal to the lamp indicator. Pressing along these rails (you'll hear a snap when they set in place) cures the problem.

....and don't forget the most commonly forgot about third brake light.