ESP,Display Visit Workshop code P0120 Please help - PeachParts Mercedes-Benz Forum

MarekW · #1 09-01-2009, 11:38 PM

I have a 2001 e320 with 103000 miles

ESP lighted up, engine running but unable to accelerate. Display Visit Workshop, the code is P0120.
It starts fine but runs at 1200 rpm and after pressing the accelerator goes to a maximum of 1600 rpm while parked.
When I drive it will go up to 12 miles per hour with the pedal to the floor.

Please any help would be appreciated

mbdoc · #2 09-02-2009, 08:10 AM

The code is related to the accelelerator potiemtiometer that controls the accelerator.

The accelerator cable connects to that potientiometer.

MarekW · #3 09-02-2009, 08:28 AM

I was reading allot about the code and it points to the throttle position sensor at the and of accelerator cable in the area of brake booster.

I am curious if I replace the sensor if this should fix my problem?

Thank you

Chris A · #4 09-02-2009, 12:36 PM

I would say yes. Mine on my SLK gave the same code and pretty much the same problem. One thing you can try. Sit in the car and push the gas pedal all the way down. Then turn the key on but dont start it. Hold the pedal for a 60 count then turn the key off. wait a few then try and start it.

That should reset the PPS

MarekW · #5 09-02-2009, 01:00 PM

Hi

I tried the reset but did not work

I am not sure if I did the reset the right way

I put key on to position # II, depressed gas pedal including the kick down switch and held it for 2 minutes, than turned off the key without removing it, waited 3 minutes and restarted the car. Went for a drive but the accelerator does not goes to max 1700 rpm and speed max 15 miles per hr

MarekW · #6 09-02-2009, 05:48 PM

I did some testing

I unplugged the plug from the TPS, than put key in position #II and measured the voltage in the plug coming from ECU to the TPS between pin 1 & 6 = 4.97v
and than between pin 1 & 3 =4.97v.

Later on the bench I supplied 5v (using a power adapter with 5V voltage regulator) to the TPS pin 1+ and pin 3- and measured the voltage between pin 3 & 4 = 0.140v.

Than 5v to pin 1+ and pin 6-and measured voltage between pin 5 and 6= 0.311v

Does this sound like my TPS is working normal and I have some other issues with my car not having response to the gas pedal?

Thank you

TMAllison · #7 09-02-2009, 06:14 PM

Quote:

Originally Posted by MarekW

Hi

I tried the reset but did not work

I am not sure if I did the reset the right way

I've not heard of that reset before, but do note that you did not do it as was instructed.

1) Insert key (pos 0), depress pedal to floor and hold.
2) Then turn key to pos 2 and continue holding pedal for 60 secs.
3) Then turn key off and release pedal.
Engine should never have started as key never went past pos 2.

MarekW · #8 09-02-2009, 06:44 PM

I just tried to do it according to instructions but still no luck, what are the other things I could try?

Thank you

MarekW · #9 09-08-2009, 11:54 PM

I have removed the throttle body and cleaned it (it was not very dirty, it looked normal).

I looked at the cable and looks fine no cracks.

The car was driven daily, but running rough lately.
The problem started when I removed wires ( 2 or 3 on driver side )from spark plugs and put them back.

Today I kind of got excited and thought I fixed the problem.

When the car was running I disconnected the air mass flow sensor, than did the tps reset and restarted the car, all power back and I was able to drive with no problems.
After shut down back to the same code p0120, ( I was able to do it 2 times and drive normal)

I have only a generic code reader and it shows p0120 only.

I am not sure what should I try next

Thank you for your input and time

Matt L · #10 09-09-2009, 12:20 AM

Quote:

Originally Posted by MarekW

I did some testing

I unplugged the plug from the TPS, than put key in position #II and measured the voltage in the plug coming from ECU to the TPS between pin 1 & 6 = 4.97v
and than between pin 1 & 3 =4.97v.

Later on the bench I supplied 5v (using a power adapter with 5V voltage regulator) to the TPS pin 1+ and pin 3- and measured the voltage between pin 3 & 4 = 0.140v.

Than 5v to pin 1+ and pin 6-and measured voltage between pin 5 and 6= 0.311v

Does this sound like my TPS is working normal and I have some other issues with my car not having response to the gas pedal?

Thank you

That thing may be called a potentiometer, but that's not what is inside. It is a piece of digital equipment. With what you did, it is unlikely that you fried something upstream, but had you tried to short two pins on the cable to the computer, you probably would.

If you need a new one, it is quite expensive. Perhaps it is available used.

MarekW · #11 09-10-2009, 10:55 PM

Just wondering if somebody have some other suggestions?

Thank you

MarekW · #12 09-14-2009, 04:49 PM

I installed a new TPS and no change , still same problem

MarekW · #13 09-22-2009, 03:17 PM

Hi

I finally had the reading from my car with carsoft 7.4 and it has the following info:

Actual error's:

p202e Actual value potentiometer in throttle valve actuator (p0120)

1. Check signal from actual value potentiometer 1

2. Check signal from actual value potentiometer 2

3.Check voltage supply (1+2)

How can I check these values and where and which pins?

Any help greatly appreciated

MarekW · #14 09-23-2009, 06:51 PM

I did more testing

I checked the 6 wires from ECU to the throttle actuator and they are all good.

I checked the resistance on wires going to actuator to one potentiometer and the other potentiometer (two pairs of wires gray and violet and also white and yellow) and was moving the flap of the actuator but there was no difference in resistance, it was a closed circuit.

Does this mean that the trottle actuator is bad or there maybe some other thing damaged?

Thank you

arstroud · #15 01-15-2010, 08:54 AM

Hello MarekW, I am having the same problem as you. I have a 2001 Mercedes-Benz C320 Base sedan in the shop right now. This also has code P202e. Your throttle is in limp mode. The code P0120 is a generic code that covers about 6 different throttle codes. The P202e version specifically states, "CAN message from AAC [KLA] control unit/comfort automatic air conditioning (N22, N22/7), CAN signal discontinuity (-)." From what I understand, the engine control module isn't getting the communications it needs from the ACC control unit (for air conditioning). I believe it needs to know AC compressor torque, Refridgerent pressure, and something else that I can't remember at the moment. What I do know, is that the ECU communicates on CAN C(100hz), and the ACC communicates on CAN B(84hz). There are three modules that communicate between both CAN frequencies, the Instrument cluster module, the steering angle module, and the EIS (EZS) control unit; however, the EIS control unit is the only one that acts as a "gateway" for control modules on differing CAN frequencies. The EIS control unit is the one that the ignition key physically fits into. I hope this helps. The C320 I am currently working on did the exact same thing that your Mercedes is doing. Erasing the ECU codes didn't make a change, BUT, erasing the codes from the ACC (KLA) module let the car drive perfectly. I am still currently trying to find where the actual fault resides. I haven't finished testing yet, but I wanted to give you a heads up. I have tested my throttle actuator and accelerator pedal position sensors and they all test good.
-Aaron
ASE Master Certified
ASE L1 Advanced Engine Performance Certified