Help with Brake Pad Sensor Lamp
 

My brake pad sensor lamp (orange) on my E420 goes on when I put the gear in Park "P". It started to do that today. Am i due for brake pad changes? Why will it light up when i am in "P"? I will see if it still does that tomorrow. istn't supposed to light up when i am driving not when i am in "P"? Thanks.

If you have your foot on the brake pedal then the light will come on if your pads are low. According to my mechanic the vehicle can still be driven. I got new pads and sensors from the parts shop on this site and will have them installed next week. My mechanic said I could wait awhile but I'd rather have brakes that are 100 percent.;)

When the light first starts to flicker there is a good amount of pad left. You have about 1000km before the pads start eating the rotors. You should be OK for a short time. Change the pads, or have them changed soon.

Lights up in park...
 

That means the parking lever is wearing out.

Re: Lights up in park...
 

I am sorry M.G. you lost me there!! What is the parking lever? I thought the sole purpose of the Pad sensor lamp was to indicate a wear in the pads and nothing else, but am i missing something? I know it sound weird, but how putting it in Park activates the pad’s sensor light? I mean without me pressing on the brake pedal. I guess I will know after i drive the car tomorrow morning if this is the case or it was just a coincidence that the lamp went on when i was in park and i had my foot on the pedal!!! Will the lamp stay on always or flickers only whenevr i press the brake pedal?

The parking lever (or emergency brake) activates the rear pads anyway, and I don't believe there are any rear sensors on that model.

Putting it in "P" locks the transmission pawl, and the sensors probably get activated with the slight motion you get when the key rotates until it reaches the pawl.

The sensor just started to come on my ML this week, and so far it only comes on when I pull someplace and "park"...kinda like Joseph_H's situation.

Driving styles dictate pad wear, but on the average, I find I have about 1500-2000 miles of pad life left before the "rivets hit the rotor"...that's a little over a month of daily driving for me...

I think I found out what's wrong!
 

I found out that the sensor wire was rubbing against the inner wheel somehow and the wire's insulation was gone showing bare wire and causing the sensor lamp to come on. I pushed the wire back enough to brake the contact and the lamp doesn’t light anymore. Looking at the pad, it got about 4mm thickness. I believe the minimum is 2mm. anyway, I’ll be due for brake job soon here and the sensors will be replaced. G-Benz is correct my car doesn't have sensors in the rear. in any case, this show that the sensor system works! simple, but works!