[Biturbos4] HELP!!! Troubleshooting DTCs w/ EPC light
dak at rochester.rr.com
Sun Nov 28 10:24:00 EST 2004
Is it really OK to just unplug the MAF? I've heard differing opinions.
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.
>> 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!
>>> 00 S4
>>> Spokane, WA but current stuck in Olympia and hesitant to crawl over
>>> the cascades under limited power
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>>> Biturbos4 at www.audifans.com
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