ddillenger

I can't comment as to WHY it is active, just that it is. As for the DTC's, they are present in the calibration, and can be tripped if conditions deteriorate far enough.

Airbag

Sorry i am not buying that any C5 uses post cat lambda control . Please direct me to any credible resource that states this .. not "other quotes" on the internet.
Newer cars do in fact use the post cat sensors ( mostly DFI engines ) as in the Audi 2.0T engine that use multiple O2 sensors and can richen the mixture to heat up the cat and burn off accumulations in the cat sensed by a mid stream O2 sensor.

But no way is this technology used on C-5

But i am open to have my mind chnged if someone can point to a credible source.

ddillenger

The screenshot below is the Bosch documentation on ME7 (The ecu in all C5's):



For those of you that can't read German, it says that when bit 0 of CLRSHK is set (to 1), Post cat regulation is off.

Here is CLRHK (the narrowband equivalent of CLRSHK) in the 559E 3.0 file. Note: It is the same in 559D and 559R.



Note that bit 0 (the last one) isn't set. This means post cat lambda control is active.

Lastly, here is the OBD fault table in the 559E. Notice the highlighted fault codes:



I used the 559E 3.0 file as that's what we're talking about here. This is the same however for ALL C5's in North America.

ddillenger

Here is more Bosch documentation, in English. Explains the function quite well.



I'm sorry I couldn't find a generalized quote that used the term "snitches" to back up my statement. I hope that the calibration documentation will suffice.

jcman

ddilinger I think there is not a clear definition between post lambda "Information" vs Control.

I'm seeing a reading from a input monitor sensor, I'm not seeing a output fuel trim adjustment in correlation.

Take a step back and really think this one over as I said before, primary engine fuel management has to start at a direct raw source not after.

My resources are: Audi Self-Study Program Course Number 941003 Engine Management Systems (185 pages in English). This is on all from the Motronic M2.3.2 up to the ME7, beginning with the M5.4.2 was the use of monitoring the three-way cat system and YES does state that the post has a role in the Long Term mixture rate it also does state that this is in ideal conditions for enrichment like cold starting, cold idle... etc. 

ddillenger

17585/P1177 - Bank2: O2 (Lambda) Correction Behind Catalyst: Control Limit Reached

17584/P1176/004470 - Bank1: O2 (Lambda) Correction Behind Catalyst: Control Limit Reached

Maybe I don't understand the position you are defending.

I am full aware of the primary o2's role in fueling, and the difference between "control" and "Information".

Consider the quality of data. Self study guide is wonderful, but it was not written by Bosch.

jcman

Both these codes are defined for the AVK 3.0 as Limit Attained not Control Limit Reached and suggest to check the intake system for leaks (unmetered air).

I would consider the Audi factory tech study guides first before the part vendor's IMO.

jcman

ddilinger Quote: I'm sorry I couldn't find a generalized quote that used the term "snitches" to back up my statement. I hope that the calibration documentation will suffice.


I was hoping that you read the source of the "quote" offering, https://www.audiworld.com/forums/sho....php?t=2580765

I doubt that Andy at Ross-Tech is not too far from the truth about a snitch aka report or inform.

ddillenger

I read the report, and I am aware of the source. The information is not entirely accurate, and has been filtered so as to make it easier to digest. The problem is that people take this rehashed information and regurgitate it as gospel all across the internet. He says the MAF and primary o2's are used. He doesn't say that is an all inclusive list.

To be honest, I'm still not sure I understand the position you've taken here. I will try to get one of the countless cars I've worked on and turn post cat lambda correction back on and then show you the fuel trims after a couple days.

jcman

That's OK, obviously you and I are stubborn and bull-headed and I like that kind of confrontation when constructively others can learn something new.

Showing the lambda correction values based on turning the post O2's values off will throw a DTC, so yes I'm curious to see the result of that "condition" vs a turned on normal one.

Then again calling or thread chiming Andy at Ross-Tech would not be out of the woods either.

The Saga goes on.