[Biturbos4] HELP!!! Troubleshooting DTCs w/ EPC light
David Kavanagh
dak at rochester.rr.com
Sun Nov 28 21:45:01 EST 2004
Ohhh, don't confuse me with the original poster! I just had the 2 lean
codes... Adam had that laundry list of codes!
Thus Spoke Michael Benno:
> David:
> Please keep us informed of what you find out.
> I personally agree with Grant, that your problem lies with the EPC
> system (Throttle Plate). Incorrect position could be causing mixture
> condionts that would cause your O2 sensors and EGT senors to be
> throwing codes.
>
> Maybe this will help. I pull this from the self study guides. If your
> running condition sounds like either of these then you may be in an
> emergency running mode. HTH...
>
> Mike Benno
> A6 2.7t
>
>
> Self-diagnosis/emergency running
>
> If a fault occurs in the accelerator position sender or the wiring,
> two emergency running programs can be run depending on fault type.
>
> Emergency running program 1: If an accelerator position sender fails:
>
> . Accelerator position limited to a defined value.
> . If a full load is predefined, the power output is increased slowly.
> . In the case of implausible signals between G79 and G185, the lower
> value is used.
>
> Prerequisite:
>
> The idling speed position must be learnt once by the intact sender.
> . The signal supplied by brake light switch for brake pedal switch F47
> indicates the idling speed.
> . Comfort functions (CCS) are prohibited.
> . The fault lamp for electric throttle control K132comes on.
>
> Note: At idling speed, the accelerator position senders G79 and G185
> are not diagnosed. If the plug of the accelerator position sender
> drops off, no fault is stored in the control unit. The fault lamp for
> electric throttle control K132 does not come on. The engine runs at
> idling speed and does not respond to the accelerator pedal.
>
> Emergency running program 2: If both accelerator position senders
> fail, driver input recognition is not possible:
>
> . The engine only runs at idling speed.
> . The fault lamp for electric throttle control K132 comes on.
>
> Safety function: For safety reasons, the throttle valve is closed as
> far as a defined angular position when both the accelerator pedal and
> the brake pedal are depressed. If the brake is pressed first followed
> by the accelerator pedal, the driver input (torque request) is executed.
>
>
>
> David Kavanagh <dak at rochester.rr.com> wrote:
>
> Thanks. I did check for boost leaks (see this :
> http://home.rochester.rr.com/dak/leakcheck/)
> I ended up replacing the leaking valve cover gasket. I haven't
> tried to
> re-pressurize the system since. I also wonder if it is really
> valid to
> pressurize at the point I did. I mean, the part between teh MAF
> and the
> turbo intake is generally under vacuum. Still, 10 psi can't be a bad
> thing to test with. If it leaks at that pressure, chances are I'd
> have a
> vacuum leak when running!
> Thanks for the tip on CEL wrt. unplugging the MAF. My apponitment
> is on
> the 9th of December, so I do have time to drive it around.
>
> David
>
> Thus Spoke Al Adler:
>
> > Yeah, if your fuel trims are that bad and the MAF is reading
> that low
> > it really does look like a MAF, especially since your're
> gettting the
> > multiplicative version of the Trim code - if you get the additive
> > version, its more likely a boost leak. One thing about the trim
> codes,
> > you'll need to drive a decent number of miles and cycle the car
> on and
> > off a few times to get the CEL to come back on after your
> experiment.
> > I made that mistake of clearing the codes and then not driving
> enough
> > myself and then took it to the dealer, they just said the MAF was
> > still ok. As soon as I got it home, the CEL was back and I just
> ended
> > up replacing the MAF myself instead of the time and hassel for the
> > dealer.
> > As the other guy says do take a look for boost leaks. Given that
> > you'll be driving at altitude even a small one could be a
> problem for
> > the turbos and these cars should probably be checked for leaks at
> > every oil change. Given how shot your MAF sounds, you may actually
> > have both problems and the MAF is just covering the leak. I
> would wait
> > on the sensors until you see how the MAF pans out; some of them
> could
> > be side effects.
> >
> > Good luck
> >
> > David Kavanagh wrote:
> >
> >> 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
> >>>>>>>
> >>>>>>>
> >>>>>>> _______________________________________________
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> >>>>>>> Biturbos4 at www.audifans.com
> >>>>>>> http://www.audifans.com/mailman/listinfo/biturbos4
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>>
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>
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> >>
> >
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> >
>
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