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TPS, Throttle Body, & Pedal Codes


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Hello.

2002 Boxster S 6-speed

I suddenly am having a problem: When the vehicle is on, the accelerator pedal does not do anything (no affect on the engine at all). I know that I have the throttle-by-wire, but here is a quick background of what I have done recently…

I changed the clutch (not really a bad job at all surprisingly) and all of the sudden I am having the pedal problem. I had cleaned the throttle body while the clutch was being done, but everything seems to be in order there (took the electronics apart and all seems to look perfect). It ran fine after the clutch job for a few days.

I have the Durametric, and it comes up with the following codes:

P1219 – Porsche Code 256 – Accelerator Pedal Potentiometer

P1578 – Porsche Code 428 – Accelerator Pedal Potentiometer

P0121 – Porsche Code 117 – Throttle Valve

P1121 – Porsche Code 430 – Throttle Position Sensor

P1122 – Porsche Code 431 – Throttle Position Sensor

P0103 – Porsche Code 115 – Mass Air Flow Sensor

So I ran a real-time watch of the sensor values, and came up with the following:

Mass air flow: 48.5 kg/h

Pedal value: 30.07%

Pedal encoder potentiometer 1: 4.54V

Pedal encoder potentiometer 2: 4.54V

Setpoint throttle: 2.98%

Actual value throttle: 116.8%

Throttle position sensor: 5.00V

Throttle position sensor: 5.00V

Throttle plate angle potentiometer 1: 116.8%

Throttle plate angle potentiometer 2: -14.1%

Mass air flow sensor: 4.99V

I have tried the “normal” fixes: car on accessory for 1 minute, then off for 10 sec, and disconnecting the MAF. Disconnecting the MAF made the car run worse, so it should be fine. I also disconnected the battery for a bit to no avail.

Can this be a problem with the pedal assembly? I see the 5V readings on the TPS, is that a broken ground or something like that? It sounds like a maximum value? The throttle body is properly plugged in, and the plug shows no sign of damage. How is this wire loomed to the pedal and computer? It disappears under the intake manifold.

Any tips would be greatly appreciated. I have only had the car for a few months, but I have put a lot into it, and I want to drive it for the final few weeks of nice weather here, and this is frustrating. 

BTW, photos of the car can be seen at:

http://www.myspace.com/cheetahonline

http://www.cheetahonline.com/vehicles/boxster.html

Thanks,

Paul

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Hmm... all of those point to bad wiring (connectors disconnected or broken wires) or all three are bad (not likely in opinion).

Only other thing it could be is a bad DME. If all teh wiring looks good then perhaps try disconnecting the battery for 5 minutes to "reboot" the DME. You will need to let the DME relearn after the reboot but just takes a little driving.

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I did try disconnecting the battery. Still no throttle. Can a bad pedal cause all of these codes? With the Durametric running, pressing the accelerator did NOT change any of the voltages to the sensors.

I am fearing wiring damage, I hope not though.

Hmm... all of those point to bad wiring (connectors disconnected or broken wires) or all three are bad (not likely in opinion).

Only other thing it could be is a bad DME. If all teh wiring looks good then perhaps try disconnecting the battery for 5 minutes to "reboot" the DME. You will need to let the DME relearn after the reboot but just takes a little driving.

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I did try disconnecting the battery. Still no throttle. Can a bad pedal cause all of these codes? With the Durametric running, pressing the accelerator did NOT change any of the voltages to the sensors.

I am fearing wiring damage, I hope not though.

Hmm... all of those point to bad wiring (connectors disconnected or broken wires) or all three are bad (not likely in opinion).

Only other thing it could be is a bad DME. If all teh wiring looks good then perhaps try disconnecting the battery for 5 minutes to "reboot" the DME. You will need to let the DME relearn after the reboot but just takes a little driving.

Dont guess, Test.

I would try a Real Diagnostic Scan Tool not an enthusiasts toy. No real Porsche Tech would use a basic scanner to get realiable data. If you do get the same results you will need a wiring diagram and will need to bust out a good DVOM and start to test for Shorts to Battery and such.

Good luck,

Vizcarra44 :huh:

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