[Biturbos4] HELP!!! Troubleshooting DTCs w/ EPC light
David Kavanagh
dak at rochester.rr.com
Sun Nov 28 11:15:26 EST 2004
yes, I have the problematic Bosch unit (no yellow dot). It reads about
107 (not 200), so my fuel trim is pegged at 25% and I get a constant
CEL. I get these codes (only);
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
P1128 - 35-00 - -
17538 - Fuel Trim: Bank 2 (Mult): System too Lean
P1130 - 35-00 - -
I have an appointment to get the local dealer to replace the MAF (since
it is still under waranty). I'd just unplug to make extra sure of the
problem. I don't want to get there and have them say "that isn't the
problem, open your wallet".
So, I could reset the codes (which also resets fuel trim), then turn the
ignition off, then uplug, then go for a test drive... if it feels
better, it confirms the diagnosis. If still feels really crappy, then I
don't know... codes at that point should show now signal from MAF (I
assume)... sounds like a plan!
David
Thus Spoke Al Adler:
> Well, I've heard of it being done many times in the Audiworld list
> without any direct consequences other than a CEL. Some people even do
> drag runs with and without to see which is better. I've done it
> breifly myself, the problem that I had is the connector was half
> broken so when I reconnected I had an intermittent short that caused
> havoc until corrected so I would take care getting the connector on
> and off. Also the ECU is then using the MAP sensor and O2 sensors to
> control the mixture so those sensors should be working. In your case
> IIRC, the B1S1 and B2S1 sensors would be important to be working, I
> think the seemingly failing B1S2 sensor would be less important since
> its primary purpose is to monitor cat efficiency. All in all I don't
> think a short test on the MAF would hurt anything, and the refurbished
> Bosch MAF's for the 2000's are below a $100 many places, including
> even the dealer so its a good part to check first since the bosch
> MAF's are very problematic.
> Al
>
> David Kavanagh wrote:
>
>> Is it really OK to just unplug the MAF? I've heard differing opinions.
>>
>> David
>>
>> Thus Spoke Al Adler:
>>
>>> 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
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Biturbos4 mailing list
>>>>> Biturbos4 at www.audifans.com
>>>>> http://www.audifans.com/mailman/listinfo/biturbos4
>>>>>
>>>>>
>>>>
>>>> ------------------------------------------------------------------------
>>>>
>>>>
>>>> _______________________________________________
>>>> Biturbos4 mailing list
>>>> Biturbos4 at www.audifans.com
>>>> http://www.audifans.com/mailman/listinfo/biturbos4
>>>>
>>>>
>>>
>>> _______________________________________________
>>> Biturbos4 mailing list
>>> Biturbos4 at www.audifans.com
>>> http://www.audifans.com/mailman/listinfo/biturbos4
>>>
>>>
>>
>
>
>
More information about the Biturbos4
mailing list