Mercedes-Benz W140 base module faults and symptoms
S 300 TD500 SEL300 SE
W140 base module: where is it and what does it do?
The base module is the control unit of the W140's electrical system. It is in the engine bay on the passenger side at the base of the windshield, under a plastic cover. The fuses are also found near it, so the check should start there.
What symptoms does a base module fault cause in the W140?
The car can go into limp mode, and the brake light and the traction control warning lights can come on in the instrument cluster. The engine can also run on only some of its cylinders or fail to start when the car is warm and is used again.
How is a W140 base module fault repaired?
First check that the module connector is fully seated: it can look connected even though the contact is poor. If the solder joints have become brittle, they are re-soldered or the module is replaced.
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