[Biturbos4] HELP!!! Troubleshooting DTCs w/ EPC light
David Kavanagh
dak at rochester.rr.com
Sun Nov 28 13:32:22 EST 2004
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
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Biturbos4 mailing list
>>>>>>> Biturbos4 at www.audifans.com
>>>>>>> http://www.audifans.com/mailman/listinfo/biturbos4
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> ------------------------------------------------------------------------
>>>>>>
>>>>>>
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>>>>>>
>>>>>
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