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mercedes bad throttle position sensor

Mercedes Throttle Position Sensor Problem

Mercedes-Benz throttle body or throttle position sensor found on C-Class, E-Class, S-Class, CLK-Class, and SLK-Class may fail to cause idle issues, no idle, or poor acceleration.

Symptoms of defective Mercedes throttle body or throttle position sensor include:

  • Rough idle
  • Mercedes won’t idle
  • High idle
  • Idle at 2000 RPM
  • Sudden idle surges
  • Check engine light on
  • Poor fuel economy
  • Limp Mode
  • Poor Acceleration
  • Fault Code such as P0221, P0120, P012x

A common problem that you may notice is that the car drives fine under normal acceleration. If you press the gas pedal to the floor or try to accelerate quickly or floor it, the engine stops responding, RPMs drop, and it may even go into limp mode. Turning off the engine and restarting it usually fix the problem. In most cases, the issue is caused by either a defective pedal position sensor or a bad throttle position sensor.

Mercedes Throttle Body

The throttle body is where the throttle valve is mounted and controls the amount of air that enters the combustion chamber; when the throttle body malfunctions, the wrong amount of air enters the engine causing problems with the air/fuel mixture ratio.

Here is a close-up picture of a Mercedes throttle body.

mercedes bad throttle position sensor

Mercedes throttle bodies made by Bosch and VDO may fail. Luckily these units are repairable. Check out these companies that offer Mercedes throttle body repair services (eBay link).

Mercedes Throttle Position Sensor

Another weak point is the throttle position sensor. On models such as E-Class W210 and W208, the Throttle Position Sensor is mounted near the front left strut, on the front of the brake fluid reservoir. Replacing takes less than 10 min and requires no special tools other than a 10mm socket and a screwdriver.

mercedes throttle position switch locationMercedes-Benz utilizes a drive-by-wire system. A faulty gas pedal (also known as a travel sensor, gas accelerator, or pedal position sensor) may develop similar symptoms as a bad throttle position sensor.

Common Causes

  • Defective Throttle Position Sensor (TPS)
  • Dirt build-up in the throttle body
  • Wiring Harness

How to fix it

First, try the throttle reset procedure

  1. Turn the key to the ON position. Position II, that is. Don’t start the car.
  2. Press and hold the gas pedal for at least five seconds. Keep the pedal pressed.
  3. Turn the ignition off but do not remove the key. Now release the gas pedal.
  4. Remove key. Wait a minute before you restart your Mercedes.

This allows resetting the High and Low points of the gas pedal. It also resets the transmission shift points to factory settings. Don’t worry; you can’t cause any damage with this reset.

Hopefully, this fixes your problem. If not, you must diagnose the throttle position sensor and throttle body. For this, you will need an advanced Mercedes scanner. 

Watch this very informative video on the function of the throttle position sensor. Excuse the sense of humor.

If you determine the throttle position sensor has failed on your Mercedes-Benz, you must address this problem immediately. In most cases, you will get code P0120 or P012x. Your options are to replace it with a new throttle position sensor. Mercedes-Benz dealerships would be happy to help you or any Indepdement mechanic. Or you can replace the throttle position sensor yourself to save money.

Check Price: Mercedes Throttle Position Sensor

If your throttle body is defective, you may be unable to repair it. An alternative solution is using a third party to refurbish your throttle body. You must remove the throttle body from your engine and ship it to companies that repair these units. Companies such as BBA Reman will test and repair your existing unit. These units are as good as new; in some cases, these companies provide a lifetime warranty for the part they repair.

List of companies that offer Mercedes Throttle Body Repair (eBay link).

In older cars, when you pressed the gas pedal, a cable was connected directly to the throttle valve, which opened and closed the throttle valve. Since 2000 Mercedes has been using drive by wire system. This means you press the gas pedal, but no cable is connected directly to the throttle valve. Instead, there is a potentiometer that detects the position of the gas pedal. This signal is sent to the Engine Control Unit, which analyzes the pedal position and several other sensor inputs and then sends the signal to the throttle body to open and close the throttle valve.

What is the Best Scanner Can I Use for Diagnosing Mercedes-Benz Vehicles?

If you’re experiencing problems with your Mercedes-Benz, the YOUCANIC full system diagnostic scanner can provide invaluable assistance in troubleshooting the issues. By connecting to your car’s onboard computer, the scanner can read fault codes and provide detailed information about any problems with your engine, transmission, brakes, and other systems. Additionally, the scanner can perform diagnostic tests on various systems, such as the ABS, airbag, and steering systems, to help identify the underlying cause of any issues.

In addition to providing diagnostic information, the YOUCANIC scanner can save you time and money on repairs by enabling you to perform simple fixes yourself. For example, if you notice the check engine light on, the scanner can assist you in identifying the problem and determining if it’s a simple issue you can address at home or if you need to take it to a mechanic. This can help you avoid unnecessary trips to the repair shop, saving you both time and money.

All in all, the YOUCANIC full system diagnostic scanner is a powerful tool that can help you maintain and troubleshoot your Mercedes-Benz. It’s an excellent investment for both DIY mechanics and professional technicians, as it can assist in diagnosing and resolving even the most complex automotive problems easily, saving you time and money on costly repairs.

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