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Most Mercedes Benzes made in 1993 to 1995 have problems with throttle bodies also known as an electronic throttle actuator or ETA. Most ETA’s problems are due to shorting wires inside ETA loom and some due to internal component failures. When ETA fails car goes into so called “ Limp Mode”. On this page you find common symptoms of faulty throttle body.

There are ASR and Non-ASR vehicles. ASR (acceleration slip regulation aka traction control) equipped vehicles enter into Limp mode with ASR and, in some cases, ABS warning lights illuminate on the dash. Symptoms: no acceleration when depressing the gas pedal until halfway down, no power on acceleration, RPMs raise and lower chaotically, idle is higher than normal, ABS and ASR warning light are on (ASR equipped cars), cruise control either doesn’t work at all or doesn’t keep preset speed or disengages. Transmission shifts rough, stays in gear and shifts at higher RPMs unless you let go off the gas pedal.

Cars that are not equipped with ASR option have slightly different symptoms-engine accelerates more or less normal, idle is higher than normal and can raise and lower by itself, cruise control doesn’t work, ABS light can illuminate on dash in some cases but in most cases “Check Engine” light is lit and codes come for ISC-idle speed control.

In both ASR and non-ASR cars transmission engages harsh due to higher than normal idle speed.

Throttle bodies made in 1993 for 600SL ONLY and all others made in 1994-1995 along with few 96 6 cylinder models have biodegradable wiring insulation that will fail and wires short. Some very few throttle bodies, about 1%, are not repairable due to wear and have to be replaced. Some ETAs, about 5%, have internal parts failures on top of shorting wires that can be repaired. In some cases shorting wires burn E-gas module in ASR cars and T/LLR module in Non-ASR cars. Those modules will need to be repaired or replaced after rewired ETA installed back into the car. It is suggested not to drive the car in Limp Mode as there are risks of burning E-gas module, damaging transmission and even engine internals due to harsh transmission engagement and higher than normal RPMs.

96-up V8 and V12 along with 97-up 6 cylinder engines ETAs are different from older units. They don’t have pigtails anymore and main harness plugs directly into ETA. These newer ETAs might fail due to internal plastic gears or potentiometer failures and need to be replaced. Since there are many of those newer used units available online they do not really make sense to repair.  

At Mercedes dealership, new ETAs prices range from $1500 up to $5400 for some V12 models each. Some of them are no longer available. And it doesn’t make sense to buy used ones as they use same biodegradable wiring insulation that can fail pretty fast. Even if ETA worked fine in the car it came from wiring fails as loom gets bent and twisted during removal. I know many people who lost money buying used ETAs that failed either right away or after some time. In the end they had their original ETAs repaired.

Some small percentage of ETAs, about 5%, have internal parts failures. One of my V12 throttle body had an internal motor failure. Motor brushes became stuck and brush holder melted. Unfortunately, that motor could no longer be repaired. But I have repaired many motor brushes, electromagnetic clutch coils, replaced potentiometer metal sliders. Before rewiring ETA internals would need to be checked first

One can check the internal wiring insulation by making 2” incision along the center of actuator loom. Outer wiring cover can be pulled apart and wires will be visible. Also, you can check the production date of some throttle bodies. Scroll down for throttle actuators general information video, removal instructions, and pictures of failed wiring insulation. And feel free to contact me for more information.

V8 engine throttle actuator removal and installation instructions

6 cylinders throttle actuator removal and installation instructions

V12 engines throttle actuators removal instructions

Limp Mode in ASR equipped car Limp Mode in Non-ASR equipped car

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