[Biturbos4] DTC 17579 on a 2000 Audi S4 (B5)

Grant gfl1 at optonline.net
Mon Apr 18 07:00:12 EDT 2005


This one drove me crazy, so I'd be happy to talk with you about it if 
need be,

Here's a short summary.

The EPC is electronic Pedal Control, aka fly by wire.  It is made of 
two components, the pedal position sensor on the pedal (measures angle 
and movement) and the motorized butterfly throttle.  What I found is 
that one, or likely both, get dirty and need to be cleaned.   Since the 
only practical way to clean them is use, its hard to isolate one from 
the other.  Also note that you *could* have a for-real component 
failure.  But so far, not one I've seen was truly a failure.

But it makes lots of sense, and correlates with problems after 
sustained use, with little movement (e.g.: highway).  The pedal sensor 
is basically a variable potentiometer.  These are known for developing 
"carbon buildup", although with today's materials, it might not even be 
carbon :-)  Similarly, the throttle body's butterfly can also build up 
dirt/carbon/whatever at the point that it moves to, through what is 
essentially a brushing action.  This problem is very typical of older 
hifi equipment, and the solution was always to turn the volume pot back 
and forth, cleaning the wiper and contact area.  Turns out the same 
applies here.

So what I found is that I needed to move both through their entire 
range of motion several times.  Yep, floor it.  Repeatedly.

I also found that it helped to clean the inside of the throttle body 
with nothing more than Gumout.  Since I figured this out, I make a 
point of periodically making sure that the pedal and the throttle 
(remember, they are not physically connected) run through their range 
of motion. This sweeps away debris in the TB, and cleans deposits on 
the pedal sensor, or so I posit.

All I can say is that Audi wanted $1000 for new parts, and I've been 
trouble -free for >2 years, despite dire predictions from the service 

If you want to chat, let me know.  Grant
On Apr 18, 2005, at 12:21 AM, Adam Jansen wrote:

> Grant
> Yes, I hooked up my Vag-Com to confirm that is the error that is 
> throwing me into EPC.
> It ONLY happens have the car has been running for an hour or two (ie 
> long trips across the state to visit my family).  Around town it is 
> fine...
> Thanks for the help
> Adam
>> From: Grant <gfl1 at optonline.net>
>> To: Single Malt <s_malt at yahoo.com>
>> CC: biturbos4 at audifans.com
>> Subject: Re: [Biturbos4] DTC 17579 on a 2000 Audi S4 (B5)
>> Date: Sat, 16 Apr 2005 16:20:11 -0400
>> Maybe I wasn;t following this closely enough.  Was this code 
>> connected with an EPC light on the dash and a transition to "limp 
>> mode"?  If so, I'll provide my experience - since the official audi 
>> repair is quite costly, and occasionally un-needed.
>> Grant
>> On Apr 16, 2005, at 4:11 PM, Single Malt wrote:
>>> --- j y <jimnetpa at yahoo.com> wrote:
>>>> Do you have the Bentley manual? The DTC section of
>>>> the Bentley manual (CD) would point you in the most
>>>> likely direction.
>>>> Adam Jansen <aedan1 at hotmail.com> wrote:I am getting
>>>> the following DTC that throws my car into EPC
>>>> 17579 Angle Sensor 2 for Trottle Actuator (G188)
>>>> implausible signal
>>>> P1171 -35 -10 Intermittent
>>> Adam,
>>> My quick Bentley search points to checking the
>>> "throttle actuation potentiometer" and it points to a
>>> procedure on how to check said potentiometer using a
>>> VAG tool.  I briefly looked at that procedure and it
>>> is a bit lengthy to summarize here, but it involves
>>> watching the values in a measuring block as you
>>> depress the throttle.  It went on to other procedures
>>> to check different components throughout this system.
>>> Another quick search for EPC resulted in a reference
>>> to the fact that a malfunction in the electronic
>>> throttle could cause the EPC lamp to come on.
>>> FWIW, hope that helps ...
>>> --
>>> Single Malt
>>> '01.5 S4
>>> Garaged at 9200ft
>>> just outside Denver, CO
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