Mercedes C Class W205 Manual Clutch Pedal Position Sensor Fault

[jm9922]

Hi All,

I got a Mercedes C Class W205 2016.

It is a manual and is not starting.

When I press the clutch to start the car says. Depress clutch fully to start.

I have put my Autel on it and it has a code in the engine ECU:

P08AA12: The position sensor 'Clutch pedal' has a short circuit to positive. There is a short circuit to positive.

Can anyone help please.
Thanks,

 

[Blobcat]

Hello and welcome,

I expect that there is a switch at the top of the pedal that isn’t activating. I’d get into the footwell and take a look

 

[jm9922]

Hi,

I have had a look and changed a part. Clutch pedal sensor. I will attach a picture of the part I changed but the fault is still the same. I did not know where the part goes as it was just underneath the plastic in the footwell.

Thanks,

 

[rf065]

Not many people buy a manual Mercedes, you might not find anyone on here with a similiar fault.

 

[supernoodle]

That pic looks like a hall effect clutch position sensor. They normally output a PWM signal with a duty cycle that varies with clutch position.
You say you don't know where that goes? Was it not attached to anything? It should be attached to the pedal assembly.

 

[davidsl500]

It probably fits to the top of the pedal or the linkage. Look for any marks as to where it might have fitted - the extent of the cable will determine the exte nt of the area it could fit..

 

[jm9922]

That pic looks like a hall effect clutch position sensor. They normally output a PWM signal with a duty cycle that varies with clutch position.
You say you don't know where that goes? Was it not attached to anything? It should be attached to the pedal assembly.

Hi,

The sensor was under the plastic in the footwell. It was not slotted in anywhere and it probably slotted out or something.

If I can find out where it goes I can then slot it there. The connector is there I connected it into the connector but it looks like it goes onto somewhere.

I checked live data on diagnostics and when I press the clutch it still shows as off.

Thanks,

 

[alexanderfoti]

My experience with these sensors is that they are hall effect but do not supply a variable PWM output. Only 2 positions, down or up. The engine ecu infers the position in between for stop/start purposes.

The code you have implies and internal electrical fault in the sensor.

If the code remains the same with it unplugged, there is likely a wiring fault.

If it changes to "there is an open circuit, or short circuit to ground" then it's likely the sensor.

 

[supernoodle]

Hmm, thinking about it @alexanderfoti , yes as that is in the footwell that must be a top/bottom of travel switch .

The clutch position sensor I'm thinking of is mounted on the master cylinder, at least on my Ford anyway. It has that in addition to TOT/BOT switches at the pedal.

I expect if that sensor in the pic above is disconnected and gives a fault with a different part description there is another sensor.

 

[jm9922]

I disconnected that sensor and I still got the same fault code. The code did not change. It stayed the same. Therefore I think it could be a wiring issue or a fuse has blown?

On the Mercedes the clutch pedal sensor looks to be the one I took out but I think I should call the dealers to see if they have any other parts listed as a clutch pedal sensor just to be sure.