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Mercedes throttle body repair. LIMP MODE ISSUES

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Many owners of 1993 to 1995 Mercedes Benz have problems with throttle bodies, also known as electronic throttle actuator or ETA. Most ETAs problems caused by shorting wiring inside ETA loom and some are due to internal parts failures. When ETA fails car goes into so called “ Limp Mode”. On this page you find common symptoms of faulty ETA and explanation of my repair service.

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 gas pedal until halfway down, no power at 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.

Cars that are not equipped with ASR option, like E320, E420, S320 have very 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 cylinders 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 computer that will need to be replaced after rewired ETA installed back into the car. It is suggested not to drive the car in Limp Mode due to failed ETA 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.

It takes some time to remove throttle actuator. On the bottom of this page you will find few videos where I talk about my experience with removal and installation of ETA into 94 SL500. There are two vacuum hoses that need to be replaced along with actuator to intake gasket. 6 cylinder motors are slightly different. ETA sits under intake on drivers side. V12 motors have two ETAs: primary with linkage on driver side and secondary without linkage on passenger side. And V8 motors have ETA in the center of the motor between intake, right under mass air flow meter. There is no need to remove intake manifolds to remove throttles.

96-up V8 and V12 vehicles ETAs are different. They don’t have pigtails anymore and main harness plug in directly into ETA. These newer ETAs fail due to internal plastic gears failures and need to be replaced.

E-class and C-class vehicles used pigtail ETA until 97. These ETAs are known to have biodegradable insulation on wiring that crack and fall off.

If you experience problems with your throttle body feel free to contact me and I will be able to repair your ETA. At Mercedes dealer new ETAs cost range from $1200 up to $5400 for V12 models each. 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 a lot during removal. I have lots of customers who lost money buying used ETAs that failed either right away or after some sort time after. In the end they had their original ETAs mailed to me for rewire.

Some small percentage of ETAs, about 5%, have internal parts failures. I have repaired motor brushes, electromagnetic clutch coils, replaced potentiometer metal sliders. These parts are examined during ETA disassembly and bench test prior to rewire and customer is informed on any issues with internals.

As of 2015 repair prices are below plus shipping and processing cost. There is 3% processing fee for PayPal or Credit Card payments. No processing fee for checks or money orders.

93-95 6 cylinders ETA rewire- $340. Many 6 cylinders ETAs have clutch coil failure. Coils are inspected before rewire.

94-95 8 cylinders ETA rewire-$375

93 (600SL ONLY) 94-94 V12 throttle rewire- $425 each. IMPORTANT NOTE: all 94-95 V12 units have internal motor design flaw. Motors brushes get stuck inside holders and if not repaired will melt holders. It is highly recommended to free brushes before they melt holders. When holders are melted complete ETA needs replacement as there are no replacement motors available. Brush repair is $200 per ETA. 93 600SL have different motors design, brushes do not fail as often.

Clutch coil or motor repair on ASR models S500, S420, E320, S320-$120

Clutch coil repair on non-ASR units, E420, S320- $300. Grinding and welding required to repair clutch coil on these models.


Below are some videos of repairs that include clutch coil problem and motor issues

Under videos you find pictures of failed wiring harnesses inside ETA looms

Mercedes throttle body, ETA, repair ASR and Non- ASR units. LIMP MODE issues

There are lots of bench test videos for my customers on YouTube.

Below is a link to my channel:



You can check the condition of your ETA wiring insulation by cutting outer insulation loom without removing ETA out the car. Or, if ETA is already removed, you can open cover on wire side and inspect wires under cover. If there are signs of insulation cracking or missing, just like on pictures below, ETA needs to be rewired before it burns E-gas module.

Feel free to contact me with any questions regarding repair process before mailing your ETA. We go over your Mercedes model, symptoms, pricing and some shipping details.

Best regards,