Tech Tip: Vacuum leak causes driver’s seat malfunction

The technician connected a scan tool but found no diagnostic trouble codes in any modules.

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May 16, 2022

Vehicle: 2010 Mercedes Benz G 550 (463.236), V8-5.5L (273.963)

Mileage: 62,764

Problem: The owner of this Mercedes G 550 was going on a long road trip and wanted his seat’s lumbar function to operate correctly.

Case Details: The technician connected a scan tool but found no diagnostic trouble codes in any modules. Since this is a pneumatic system, next the technician accessed the lumbar valve body in the back of the seat to see if there was any signs of leaks or damaged lines. This system can also be pressurized like an evaporative (EVAP) system with a smoke machine to locate a leak. Additionally, this system has a similar safety function as air suspension. It will shut the air pump off if it detects any loss in pressure. The technician smoke tested the seat’s pneumatic system and found the leak coming from the hose manifold under the carpet.

Confirmed Repair: He replaced the damaged hose manifold assembly as a unit and the lumbar function worked as designed. Problem solved!

Reprinted with permission from ALLDATA

About the Author

Richard Diegle

Senior Automotive Editor for ALLDATA

Rich Diegle has been in the automotive industry since 1978. After graduating from a local community college, he began working at a Nissan dealership as a used car technician. Since then, he’s worked as a Nissan and ASE master automotive technician, shop owner, marketing copywriter, automotive editor, public relations manager, instructor, ALLDATA Tech-Assist team manager, and a senior automotive editor.