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Pete
Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 29116
Experience:  Over 15 years experience as a Mercedes dealer technician
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2001 E320 appears to be in limp mode - OBDII generic code

Customer Question

2001 E320 appears to be in limp mode
- OBDII generic code P0120
- ESP light on dash
- TPS appears to have good voltage (5.0 across pin 1 and 3 and 1 and 6), and continuity to harness is ok from TPS to ECU
- I can reset the TPS using gas pedal, and clear codes - engine will respond and accelerate; then immediately throw the ESP light and go into limp mode.Car ran fine until I changed the TXV valve and tried to service the A/C - as part of this service I also flushed the evaporator coil. Some flush under the TXV valve and around wiring loom. I'm at a loss... but I think it must be related to the ESP code.. and not anything related to TPS or generic trouble code.I don't have MB scanner or software. Checked MAP sensor continuity to ECU and that looks good as well.
Submitted: 2 months ago.
Category: Mercedes
Expert:  Pete replied 2 months ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

The code set is for the accelerator pedal position sensor at the pedal assembly.This sensor can test and read properly then suddenly act up intermittently out of the blue like your seeing here.It causes a limp mode when it acts up and is normal to cause the limp mode to prevent any acceleration issues.

This sensor most likely failed the same time the work was done and is not a result of the repairs you had done here.

The gas pedal assembly has to be replaced as it comes with the sensor and will resolve this fault here.Unfortunately this is a common issue and I have had to replace the pedal assembly for this issue here.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 2 months ago.
there is another sensor at the gas pedal assembly? looks like just a cable to the throttle position sensor which is under the hood.
Expert:  Pete replied 2 months ago.

I apologize as I had the incorrect year input.There is a cable to the throttle actuator as shown below and on this actuator is the sensor ( B37) that can fail.

https://www.dropbox.com/s/j83foorj27n7ibx/ped-07-25.gif?dl=0

If this sensor is acting up it will cause this fault here with it needing replaced.It is part of the actuator assembly or throttle assembly as shown above.

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time.Your 5 star rating is appreciated

Thanks Pete

Customer: replied 2 months ago.
new pedal sensor installed.... set pedal sensor with gas pedal... codes out and goes to limp mode as you accelerate one time. any other suggestions? this one was 225 bucks and problem persists.
Expert:  Pete replied 2 months ago.

Same code again?

Customer: replied 2 months ago.
same code and right back to limp mode
Expert:  Pete replied 2 months ago.

I thought for sure that would fix it as that is the most common issue.I apologize.Below is some info on testing and checks to locate the source of the fault as this may help here.It may be a wiring fault or the ME ( engine computer at fault).

https://www.dropbox.com/s/hs3jdbadsmk0k4h/14-07-25.gif?dl=0

https://www.dropbox.com/s/14gyc9eude7vsij/15-07-25.gif?dl=0

https://www.dropbox.com/s/b98ofbd1vl6j0iy/16-07-25.gif?dl=0

Keep in mind allot of this testing is usually done with a dealers SDS ( star diagnostic) machine plugged into your vehicle to run through the testing procedure.

M16/6r1 (Throttle Valve Actual Value Potentiometer) : Line Mixed Up (P0120)

Check Component M16/6 (Throttle Valve Actuator).

Test 1 Check Component M16/6 (Throttle Valve Actuator) Using Actual Value.
Test 2 Test Component M16/6m1 (Actuator Motor) by Actuation.
Test 3 Test Internal Resistance of Component M16/6m1 (Actuator Motor).
Test 4 Test Internal Resistance of Component M16/6 (Throttle Valve Actuator).
Test 5 Test Voltage Supply of the Potentiometers of Component M16/6 (Throttle Valve Actuator).

1 Check Component M16/6 (Throttle Valve Actuator) Using Actual Value.

Test requirement
- Ignition ON

Status of the relevant actual values:
- M16/6 (throttle valve actuator) Signal 1: Note! Communication with ECU required
- M16/6 (throttle valve actuator) Signal 2: Note! Communication with ECU required

Specified values
- M16/6 (throttle valve actuator)Signal 1(Accelerator not operated): [0.30...0.90] V
- M16/6 (throttle valve actuator)Signal 2(Accelerator not operated): [4.20...4.60] V
- M16/6 (throttle valve actuator)Signal 1(Kickdown switch operated, accelerator fully depressed):[1.30...1.70] V
- M16/6 (throttle valve actuator)Signal 2(Kickdown switch operated, accelerator fully depressed):[3.30...3.70] V

Question
- Are the actual values o.k.?
Yes
The actual values are okay. ** End of Test **
No
At least one of the relevant actual values is not okay.
Possible cause and remedy
- Test internal resistance of component M16/6 (throttle valve actuator).
- Test voltage supply of component M16/6 (throttle valve actuator).

** End of Test **

2 Test Component M16/6m1 (Actuator Motor) by Actuation.

Test requirement
- The engine is running.

Note
- If the throttle valve angle is < 1,1° DK, there is unmetered air present.

Note: Component M4/3 (engine/AC electric suction fan) runs with an on/off ratio of 50 % during the actuations for safety reasons.

Note! Communication with ECU required.

3 Test Internal Resistance of Component M16/6m1 (Actuator Motor).

https://www.dropbox.com/s/uhi93wvqb9uhb0a/17-07-25.gif?dl=0

Test sequence
- Switch off ignition.
- Unplug the socket 1 at component N3/10 (ME-SFI control module).
- (N3/10) 1.6 <--> 1.3 (N3/10)

Specified value
- Resistor[1...10] ohms

Question
- Is the measured value okay?
Yes
The measured value is o.k. ** End of Test **
No
The measured value is not o.k.
Possible cause and remedy
- Wiring between N3/10 (ME-SFI control module) and M16/6m1 (Actuator motor)
- M16/6m1 (Actuator motor)

** End of Test **

4 Test Internal Resistance of Component M16/6 (Throttle Valve Actuator).

https://www.dropbox.com/s/72jbtntqhki795g/18-07-25.gif?dl=0

Test requirements
- The throttle flap of component M16/6 (throttle valve actuator) should operate freely and must not stick or rub.
- At least one of the relevant actual values is not okay.

Test sequence
- Switch off ignition.
- Remove air scoop at component M16/6 (throttle valve actuator).
- Unplug the socket 3 at component N3/10 (ME-SFI control module).

M16/6r3 (Actual value potentiometer (sliding contact 1))
- (N3/10) 3.21 <--> 3.22 (N3/10)
- Slowly operate throttle flap by hand up to full load.

Specified values
- Idle speed[ca. 1380] ohms
- Full load[ca. 480] ohms

M16/6r4 (Actual value potentiometer (sliding contact 2))
- (N3/10) 3.20 <--> 3.22 (N3/10)
- Slowly operate throttle flap by hand up to full load.

Specified values
- Idle speed[ca. 650] ohms
- Full load[ca. 1490] ohms

Question
- Are the measured values okay?
Yes
The measured values are o.k.
Further possible causes of fault
- Test voltage supply of the potentiometers of component M16/6 (throttle valve actuator).
No
The measured values are not o.k.
Possible cause and remedy
- Leads to component M16/6 (throttle valve actuator)
- M16/6 (throttle valve actuator)

** End of Test **

5 Test Voltage Supply of the Potentiometers of Component M16/6 (Throttle Valve Actuator).

Test requirement
- At least one of the relevant actual values is not okay.

Test sequence
- Switch off ignition.
- Unplug the socket 3 at component N3/10 (ME-SFI control module).
- Connect adapter cable no. 210 589 05 63 at component N3/10 (ME-SFI control module).
- (N3/10) 3.19 <--> 3.22 (N3/10)
- Switch on ignition.

Specified value
- Voltage[4.75...5.25] V

Question
- Is the measured value okay?
Yes
The measured value is o.k.
Possible cause and remedy
- Inspect cables from component M16/6 (throttle valve actuator) to component N3/10 (ME-SFI control module).
No
The measured value is not o.k.
Possible cause and remedy
- N3/10 (ME-SFI control module)

** End of Test **

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time.Your 5 star rating is appreciated

Thanks Pete