[Biturbos4] HELP!!! Troubleshooting DTCs w/ EPC light

Al Adler adlere at sourcecodecorp.com
Sun Nov 28 10:07:19 EST 2004

Two things - fuel trim codes can indicate a bad MAF. One thing to try is 
to unplug the MAF and see if the car drives better. Secondly, I believe 
B1 is the passenger side - I have a B1 S1 sensor on its way out so I 
have done some research on the issue. Still, consult a more qualified 
source before yanking parts. I would also check the o2 and egt wiring, 
as was already mentioned. You seem to have a lot of codes from the rear 
of the engine so maybe they'res some damage back there.

Grant wrote:

> Ahh, something I have some experience with  ( I was about to write 
> "know something about, but that may be overstating the case a bit....).
> Let's start with EPC and what it is. EPC is "electronic pedal 
> control".  The 00+ S4s are "fly by wire" cars which transmit pedal 
> angle (from a sensor) to a throttle body stepping motor which in turn 
> controls the butterfly angle and opening.  The EPC light indicates 
> that your problem is within this system.  I've had the same gremlin 
> and, at least, had the "pleasure" of chasing lots of false problems.
> Given the above, I'd speculate that a large number of your codes (all 
> the O2 and mixture stuff) are related to a different problem (probably 
> O2 sensor).  But the last code:
>> "17579 - Angle Sensor 2 for Throttle Actuator (G188) Implausible Signal
>>            P1171 - 35-10 - - - Intermittent"
> Is exactly the one that I got (and occasionally continue to get).  
> What it means is that the sensor sends back a butterfly angle that 
> seems impossible given the throttle position, load, etc.  It can 
> actually be either the pedal sensor or the throttle motor.  I never 
> found out *for sure* the source of the problem, but I'd bet heavily on 
> the following culprit, and I bet it will affect all of us sooner or 
> later:
> The scenario:
> The throttle body is dirty.  The butterfly, as it wipes back and 
> forth, slowly builds up a ridge of dirt in the throttle body, which 
> the butterfly subsequently "catches" on - either in the forward or 
> reverse direction.  I speculate ( as does on of Audi's regional 
> training techs) that this is partially caused by a limited throttle 
> angle in normal driving.  (e.g.: the car is very powerful and/or I'm a 
> wussy).  If the butterfly rarely gets past this point, a ridge of 
> fairly hard dirt builds up and you're on your way to trouble.  I got 
> to the point where this happened daily, or at least weekly.
> A new TB, Audi's suggestion (gee, thanks Audi) was $1000 + install, 
> which made me hesitate and figure all the above out.  I did talk to 
> several audi techs, but the only real proof I have is that I made the 
> problem go away on my car and one other.
> The solution has two parts:
> 1) Move the butterfly through its motion several times.  In general, 
> you get to have fun doing this part (yes, I mean go out and stomp on 
> it - but the goal is butterfly motion, not engine revving, so high 
> loads at low revs are actually best).  Make sure you move the 
> butterfly through its motion and back several times, and do this on 
> occasion just to keep it "swept out".
> 2) If you can, get some gummout into the TB and clean it. The trouble 
> here is getting access to the TB.  You need to remove the two snorkels 
> that come up from he intercoolers, and one of them is a bear to get 
> out, due to a snap-fit in a plastic track.  I'd hate to break 
> something in there (maybe have your local, friendly garage do it).  If 
> you decide to do it, you might look at the "throttle body boot 
> replacement" instructions posted on the tech part of AudiWorld as a 
> sort-of guide to removal.
> I've had one recurrence after ~ a year, whcih was quickly exorcized by 
> a deep exploration of pedal travel later that day.  Feel free to email 
> me with questions, and don't panic.  Very likely its not $1000, but 
> rather 2 hours, gummout, and a heavy right foot.
> Grant
> On Nov 27, 2004, at 9:39 PM, Adam Jansen wrote:
>> As I was driving over the Cascades to visit family for the holiday, 
>> the EPC light comes on the the power cuts out (not fun coming up 
>> Snoqualmie Pass!)
>> I dont have my Bently or family albumn with me, but luckily I did 
>> have the laptop and pulled these codes:
>> 17526 - Oxygen (Lambda) Sensor Heating: B1 S2: Open Circuit
>>            P1118 - 35-00 - -
>> 17522 - Oxygen (Lambda) Sensor: B1 S2: Internal Resistance too High
>>            P1114 - 35-00 - -
>> 16524 - Oxygen (Lambda) Sensor B1 S2: No Activity
>>            P0140 - 35-00 - -
>> 17866 - Exhaust Gas Temp Sensor 2 (G236): Short to Ground
>>            P1458 - 35-10 - - - Intermittent
>> 17536 - Fuel Trim: Bank 1 (Mult): System too Lean
>>            P1128 - 35-00 - -
>> 17538 - Fuel Trim: Bank 2 (Mult): System too Lean
>>            P1130 - 35-00 - -
>> 17579 - Angle Sensor 2 for Throttle Actuator (G188) Implausible Signal
>>            P1171 - 35-10 - - - Intermittent
>> I am replacing the O2 sensor in the morning (driver's side rear 
>> correct?) but I am worried about the Throttle Actuator and the System 
>> running lean!
>> I stopped when the light came on and then started off again as the 
>> light turned off... it seems that the EPC light with the above codes 
>> (expect the O2 sensors readings) come on only after the engine has 
>> been running on the highway for 30-45 mins, which just adds to the 
>> frustration of trying to fix it!
>> ANY help would be appreciated!
>> Thanks
>> Adam
>> 00 S4
>> Spokane, WA but current stuck in Olympia and hesitant to crawl over 
>> the cascades under limited power
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