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Accelerator Pedal Not Working

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Hi all, I have a 2000 Boxster S, manual transmission, and I'm in the USA.

Yesterday I was driving the car and all of sudden the accelerator pedal stopped working. It didn't matter how hard or easy I pressed the pedal, the engine RPMs did not change. I pulled over and the car just sat there idiling. I turned off the car and restarted, but no pedal action.

I was able to get the car home since I was only a mile away. This morning the car would just barely start and stall again.

I pulled out the Durametric and I received the following codes:

P1219, Porsche fault code 256 - Accelerator pedal potentiometer, Signal implausible


P1578, Porsche fault code 428 - Accelerator pedal potentiometer


P0121, Porsche fault code 117 - Throttle valve, Signal implausible


P1121, Porsche fault code 430 - Throttle position sensor, Signal implausible


P1122, Porsche fault code 431 - Throttle position sensor, Signal implausible

I find it hard to believe that both the accelerator pedal potentiometer and the throttle position sensor would go bad at the same time.

I recently put in an EVO Intake and Headers (had the O2 sensor moved behind the 2nd cat), but the car was working fine with both of these installed.

Has this happened to anyone before or do you have any suggestions? Your feedback and thoughts would be appreciated.


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You are right to believe that both the accellerator and electronic throttle valve both failed at once, most likely if codes are erased all codes will return right away. I have had one customers car (also a boxster S) that had similar codes, sadly it required a dme control unit to repair.

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I’ve never had problem but you could think of it this way, the pedal potentiometer sends out an “implausible” signal (and it snowballs into several throttle related codes).

Then the throttle body receives garbled “implausible” signals from the “pedal potentiometer” and throws out it own “WTF” signal which intern snowballs into multiple throttle body relate codes. I would not be surprised if you really only has one problem

It just seems to me that error codes seldom come in onsies’

Good luck, PK

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  • 3 weeks later...

Update: I had the car towed to my local independant Porsche mechanic and he diagnosed it as a bad DME. He said he's seen this problem about 5-6 times since the e-gas started in 2000. The part is currently on order. I'll report back once it arrives and let you know if that solved the problem.

Thanks guys!!

Edited by dmenn
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