Brake Lights Stay Illuminated
 

Car: 2001 E430 4Matic
Presumed Problem: Brake Light Switch?


Got ABS/ESP/BAS error lights today.

After shutting down and restarting, shifter was locked and I used mechanical pencil to unlock it via that special port. Error lights were gone, no malfunctions were reported, but the shifter remained stuck in Park on the next restart.

Luckily it got dark soon and the problem became clear: The brake/stop lights are stay illuminated when the car is on. Brake switch plunger must be stuck in the depressed position?

Obviously the brake light switch is faulty but is it common to fail in this way -- with lights stuck on and no further ABS/ESP/BAS lights?

Drove to dealer this morning to get replacement brake light switch. Not surprisingly, the moment I entered the parking lot I heard a click and the stuck switch released itself. Shifter no longer locked into park but the BAS/ESP/ABS lights illuminate as soon as I tape the brake pedal, and I do not appear to have brake lights.

I was told the replacement part is an upgraded component and actually comes with installation instructions (photos attached). That said, what , is a “Feeler Gauge?” Looks to me like a skinny screwdriver.

Obviously you've answered your own question at this point, but the BLS can fail in a few different ways; yours is the most obvious and potentially worst because you can drain the battery if you happen not to notice it (easy enough in the daytime).

Luckily it's relatively inexpensive and simple to replace. And you were smart to get the replacement at the dealer, the aftermarket ones seem to be buggy.

Good luck.

A feeler gauge is a precision measuring tool used to measure clearances (space) between two objects. They resemble flat blades and are marked with their thickness. You normally purchase them as a set but a single feeler gauge is also available at your auto parts or tool store.