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Discussion Starter · #1 ·
My 2002 Mercedes S500 is my only vehicle and is NOT STARTING. Any suggestion or insight after reading would be very helpful at this point!!

1. First I noticed the rear lights were not going off even with the headlights turned off and the car off.
I returned to a dead battery.
When attempting to jump it, noticed the lights were still stuck on but only one side of the taillights were illuminated
2. Car would not jump; so I replaced battery with a brand new one. Car still would not start, it would crank but not ignite.
3. Thinking it may not have sufficient fuel, I put 3 gallons in. Gas did not seem to register on gauge.
4. Ran ODB reader on it - 1 code retrieved - Fuel level sensor.
5. Since car would not start AND lights seemed to still be stuck on, I kept battery disconnected and would reconnect when attempting to start. I noticed all lights flickering the last time.

  • Mileage is 160k
  • Replaced battery less than a year ago, have killed it a few times due to leaving interior lights on
  • Airmatic suspension stopped functioning properly recently due to a suspected leak in the rear passenger airbag.
  • Streets have been flooded - and with car being too low to the ground due to the aforementioned, I suspect some potential for damage? Not sure which components would be exposed...
  • Car has never overheated/gotten hot
  • I have run my car out of gas several times and consistently drive on/close to E

I really need my car; I can't get to work or take my son anywhere etc.

Where should I begin to diagnose/address the problem? If something is majorly wrong, shouldn't more codes be thrown than just for the fuel gage?
Has anybody experienced any of this?
Please let me reiterate that any advice would be extremely helpful!!!! Thank you!!!!

· Registered
2003 S500 2007 GL450
4,110 Posts
The problem with the rear lights and fuel gauge lead me to suspect that you have water damage to the rear SAM (Signal Acquisition Module) located under the right rear seat cushion.

A known problem with the W220 (which includes your model) is that the small drain in the HVAC (cabin air inlet) plenum under the hood gets easily plugged by leaves and debris. When it does, rain or wash water fills the plenum (under the large grille at the rear of the engine compartment), and the water then over flows into the car under the carpet.There will be no visible sign of water in or above the carpet! This water will flow under the carpet and padding and soak the electrical wiring, connectors and fuses under the carpet, padding and an aluminum cover. This will cause corrosion and serious electrical problems. The water will continue to flow to the rear of the passenger compartment under the rear seat into the rear SAM, where it will cause corrosion and serious damage to the fuses and control modules inside the SAM.

The only way to check for water and the damage that it causes is to lift the right side carpet and padding, remove the aluminium cover and carefully check for moisture and corrosion. The top of the carpet will not be visibly wet. There may or may not be any trouble codes.

If there is moisture, the only way to repair the problem is to:
Snap off the black grille covering the plenum. Remove the small valve at the bottom of the plenum and reinstall the grille.
Remove the right front seat and the right side carpet, padding and the aluminum cover panel.
Completely dry the carpet and padding, which will take several days of serious drying.
Disconnect the battery ground cable under the right rear floor of the trunk.
Carefully disconnect, disassemble.and thoroughly clean every electrical connection under the carpet.
Under each front corner of the rear seat cushion is a small lever. Press the lever sideways to release the rear seat, then lift the rear seat bottom up and out.
Carefully inspect the rear SAM for any traces of moisture or corrosion. Partial or complete disassembly may be required.
After drying, cleaning and reassembly of all of the electrics, reattach the ground cable, and check everything for proper operation.

Yes, it is somewhat difficult. Yes, if there is moisture under the carpet, everything above is mandatory.

There are quite a few threads, posts and videos on the problem. Google is your friend.

This may or may not be your problem - Good Luck!

In addition, another known W220 problem is failure of the engine crankshaft sensor. This is a relatively cheap and very easy repair. Again, Google is your friend.

For more info on both possibilities, go to the Encyclopedia in the thread near the bottom of the light blue area ("START HERE") and start drilling down hunting for these two possibilities. Good Luck!
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