Hi All,

Picked up my first Porsche about 3 months ago now, enjoying every minute of it! She is an x50 with 54k~ on the clock



Just before xmas she went into the OPC for a basic major service (oil/oil filter/pollen filter/air filter). I then carried out Gearbox oil/spark plugs/clutch accumulator/fuel filter/brake fluid change.

(old man analyzing a wheel nut!)


The car the ran fine for a week or so including a 6 hours journey. On the way back she went into limp mode (0.1bar of boost) but no warning lights. Car seemed to run fine apart from lack of power. I disconnected the battery and she ran fine for a few days then went into limp again.

At this point I decided to order a PIWIS cable to read the codes off:

P2135
Accelerator pedal
Signal implausible

P0121
Factory Fault Code 117 - Throttle value or accelerator pedal potentiometer
Signal implausible

The codes appear before engine start with ignition key at 1pm. I can clear them with ignition off but they reappear as soon as the key is back at 1pm. Since then I have tried an egas reset after battery disconnect which made no difference (codes reappeared instantly).

With some help off the uk forum I have compared some actual values with a working car - key at 1pm (engine not started) :

Value at idle / value at WOT (my car in red, base car in black)

pedal value 0% / 99.99% 0% / 30.07%
pedal encoder potentiometer 1 0.76volts / 3.3volts 0.74volts / 3.44 volts
pedal encoder potentiometer 2 0.38volts / 1.65volts 0.54volts / 1.84volts
specific throttle plate angle 4.2% / 99.99% 4.24% / 11.37%
actual throttle angle 4.2% / 99.9% 5.8% / 11.3%
throttle position sensor 1 0.78volts / 4.35volts
throttle position sensor 2 4.25volts / 0.67volts
throttle plate angle potentiometer 1 6.2% / 99.6% 5.4% / 11,3%
throttle plate angle potentiometer 2 5.8% / 99.6% 5.4% / 11.3%

Now am I right in assuming limp mode is causing the pedal value to stay at 30%? e.g. not an error with the system?

Has anyone seen these codes before? I've tried searching but no solid answers were found.

Plan is to remove pedal & potentiometers and clean connections, if this fails i'll look to clean throttle body?

Any advice would be greatly appreciated!

 

For P2135....check/replace pedal sensor
The system operates in pedal sensor standby mode, i.e. the
angle of the accelerator pedal is calculated from the residual
position sensor signal.
♦ The maximum pedal value is limited to 30 %.
♦ The dynamic is limited.
♦ The fault code only appears together with P0121 or P0221.
♦ The pedal value is reset to zero by actuating the brake.

For P0121:
Possible fault cause
♦ Open circuit or short circuit in the wiring
♦ Throttle position sensor faulty
♦ DME control module faulty

 

Wow nice help.

 

if you dont have already
here is the link for some workshop repair manual
i believe there is some 996tt stuff

https://www.6speedonline.com/forums/...nual-cd-8.html

 

That's pretty Congrats on the purchase and great too see your old man helping you out, miss those days. Enjoy and keep us posted.

 

Thanks for the comments (and help!). Going to take the pedal assembly apart this weekend and have a good look at the sensors, will go from there!

 

Did you have any problems over the weekend ?

 

Thanks for the follow up - very kind of you.

I didn't get as far as I would have liked. I did manage to clear the faults and pedal value went up to 99% as did everything else:

WOT No Throttle


Do these look out of the ordinary?

I was also able to start the car without any values returning but the moment I drove down the road it had reverted back to 30% and the codes had reappeared. Unfortunately I ran out of daylight so haven't had a chance to pull the pedal assembly apart yet - a job for this friday!

Will update the thread with my progress

 

Those second values look good to me.
Unfortunately, the problem could be in either your pedal or your throttle body (or the wiring between the two). Since limp mode limits the throttle value to 30%, that would account for the values you were getting prior. Determining what's putting it in limp mode is the tricky part.
I would check the throttle body electrical connection (unplug it, check for corrosion at the terminals, make sure the connector seal is in its proper place). Any chance that plug was disturbed during the air filter change?

 

Thanks for the reply, I will take a look. The air filter change was carried out at the OPC but I suppose anything is possible! It's also been very wet recently and I have become aware how wet the engine compartment becomes if you open lid!

 

Just to wrap this thread up (for future searches out there) the culprit was the throttle poteniometer:



Worth mentioning this part is shared with the 986 Boxter range. 3 Bolts and unclipping the connector is all it took

Thanks for all the help!

 

Good to see you got it figured out! Thanks for updating the thread.

 

Thanks for sharing the fix!

 

Thanks for closing out this issue Shanty. Too many of these questions disappear without finding out what the root cause was.