I was driving the other day on the highway, and out of nowhere, my dash started beeping....saying my doors were open wen then werent. then my interior lights went out....i went home, next morning...i turned the car on, and my gas guage isnt working, and none of my tail lights are working....i tried taking the bat out for 30mins, and all of that....anyone know about this prob? what i should get replaced? or something.....

that would be great. Thank you!
_Dean

 

Hi Dean,

This is a difficult one since I believe more info is required to provide a definite response.
Think real hard. Anything else happen that might pinpoint the problem?

Weather.
Servicing
How long have you had the car. i.e. How long has it been OK for.
Anything.

These symptoms are however very common on SLK in which model the problem is caused by the PSE (Pneumatic Control Unit).

I've never experienced a PSE go on the S Class since it is located in a dry spot behind the LH boot liner. The PSE is a black box with lots of yellow tubes going to it. Do you happen to park your car nose down a slope i.e. on your driveway. This causes the rear channels either side of the boot to fill with water (until the car is on level ground) and a defective boot seal may find water getting towards the PSE. Just a thought.

The PSE controls Security, Rear Lights, Interior Light, Alarm etc and does so by sending digital signals down the main data highway (CAN) to other modules located in the engine bay. The door switches are of course a key part of the security,door lock and interior light systems.

The problem is due to corruption of this CAN but this could occur anywhere on the network BUT is usually due to water / corrosion across the Hi and Lo CAN wires (Green and White) due to water ingress into the CAN at the PSE (on SLK).

Spilt drink near gear lever? Car wash water into control box at back of engine bay, etc etc.

A "body electrics" scan will give more clues but you will need dealer help for this.

A COMMON problem on S Class W220 is the heater air intake filling with water and then "flooding" the car and electrics. Are you sure the drain in the plenum has been checked and if necessary cleared?

Good luck. Let us know how you get on.

Stuart