Mercedes Siemens VDO and Mercedes Bosch “drive-by-wire” electronic throttle bodies commonly fail, resulting in rough idle, no idle (engine won’t start/turn-over), poor gas pedal-to-throttle response, and/or random loss of acceleration while driving (common and extremely dangerous). These affected “electronic throttle control” systems are ones fitted for Mercedes C/E/S/CLK/SLK class models as early as 1998, often reported failing after 100,000-130,000 miles. Failure is often due to one of these determinants:
- Faulty “throttle position sensor” (TPS) inside the throttle body. Basically, this intricate potentiometric sensor fails, usually accompanied by an ODB-II DTC error code and visible error message to the dash.
- Faulty “DC motor” inside the throttle body that rotates the pinion gear to the spur gear. Basically, the DC motor burns out and does not turn the gears to open the throttle plate/butterfly to let air into the intake manifold.
- Faulty “wiring harness” outside the throttle body. Basically, corroded, broken, or disconnected wires in the plastic harness, or bad connections to the Engine Control Unit (ECU).
To fix this (fairly expensive) part, you can take 1 of 3 actions:
- Repair your existing throttle body. This is the least expensive option. This option is reasonably reliable if performed by an expert technician.
- Replace your throttle body with a used or remanufactured part. This can be less expensive than a new part and more expensive than repairing your existing part. This option can be reliable if the used replacement part has been adequately tested and/or remanufactured.
- Buy a new throttle body. This usually is the most expensive option. This option is most reliable.
IMPORTANT NOTE: Whichever action you take — repair, buy used, buy new — you will need to follow a procedure to “re-learn” your throttle body after installation so that it optimally communicates with your car’s ECU. This is fairly simple to do and can be done without going to a Mercedes dealer. This example shows a 2001 Mercedes C240 3.2L V6 with 130,000 miles on the original Bosch “drive-by-wire” throttle body (Part # 112 141 01 25). Throttle bodies (a.k.a. throttle body actuators)