Assistance required: 320CDI BAS/ABS warning, inoperative brake lights, defective alternator/battery.

[eggnogx]

I am experiencing an unusual issue with my E320 W210. Bas/abs varnings are on since i have no brake lights. I replaced the switch, but there was no impact whatsoever. I get codes using Launch Scanner: C1200 brake light switch S91 P0703 brake signal plausibility.

The brake light switch receives electricity and activates when being pressed.
While testing the light bulbs, I saw that when I placed the iron "pen" on the light bulb, all three brake lights activated. I suspected a grounding issue; however, adding an additional ground wire had no impact.

I am devoid of ideas. I cannot go anyplace since my automobile has remained stationary for around 1.5 years at the location where I purchased it.

Furthermore, I possess no knowledge. Defective alternator or battery. No improvement after battery replacement; the alternator functions as intended.
Codes that I believe are interconnected:
B1123 incorrect authorization data
B1129 transmission malfunction

Any assistance would be appreciated.

[shakee]

What is the model year of your vehicle?
Do you provide ESP or ASR as traction options? (Check for ASR or ESP button on the center console).

I observed that when I lay the iron "pen" against the light bulb, all three brake lights activate.

What is the significance of this? Kindly elucidate your actions.

[eggnogx]

I am referring to the "pen" cable in the voltmeter; I apologize for not knowing its proper name. However, I am interested in anything composed of iron.

[shakee]

I remain uncertain. When you state, "I observed that when I connect the iron 'pen' to the light bulb, all three brake lights illuminate," which specific light bulb are you referring to, and where on the light bulb do you put the "ground" or 12V? The three brake light bulbs possess distinct power supply and grounding, making them mostly independent of one another.

I inquired if your vehicle is equipped with the ESP or ASR feature. When ESP is enabled, a relay suppresses the brake lights. In the absence of such relay, the brake lights will be inoperative.

Did the issue present at the time of purchase, or did it arise subsequent to your actions?

[eggnogx]

Apologies, it is equipped with ESP.

I will simplify: the rear light bulbs are dual-function, possessing two sockets for each illumination string inside the bulb. Consequently, if I insert any metallic object into the brake light socket, all three brake lights will activate. Which is the peculiar aspect..
I apologize; I am not a natural English speaker.

[shakee]

It seems that you are shorting the tail light terminal and the brake light terminal. You may be backfeeding 12V from the tail light pole to the brake lights, which is inadvisable since it may lead to blown fuses over time.

The brake stop light switch has 3 pairs of connections for automobiles with Touchmatic gear shifters. The first pair is designated for the brake lights (thick poles), which are often in an open state. The second pair pertains to the traction system (ETC/ASR/BAS/ESP) and is often in a closed state. The third pair is designated for the gear shifter and remains generally open when the brake pedal is withdrawn.

The brake light signal is sent to a relay contact (K55) located under the hood near the 38-pin connection socket with the Electronic Stability Program (ESP). The relay contact is ordinarily closed, but when ESP conducts the braking while driving, it opens the relay to silence brake lights. A defective or absent relay will result in a malfunction of the brake lights. This may be or may not be your issue, but it is simple to check.

[shakee]

[shakee]