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Title: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on April 11, 2011, 12:23:37 AM Despite popular belief that the secondary O2 sensors are for emissions puproses only, I am seeing evidence that they actually have a fairly large impact on performance.
It all started when I gutted my pre-cats. I installed double-stacked spark plug defoulers to avoid the dreaded CEL from catalyst efficiency codes. When I did this, I did not drill them out at all as some have suggested. I had believed this was done solely to accommodate the sensor and instead used the spacers provided with the defoulers. After a short while, I began experiencing an significant loss of power during part throttle (almost no off-boost power) and my CEL began coming on every 800 miles or so. A quick scan with VAG-Com displayed P1176. 1 17584/P1176/004470 - Bank1: O2 (Lambda) Correction Behind Catalyst: Control Limit Reached I did not think much of it at the time, so I just cleared it when it came up and continued on. At some point I decided to check the code in the Bentley and was very suprised by what I found. Quote from: Bentley Oxygen sensor control behind the catalytic converter is responsible for final control correction. It is the primary sensor and can override the signal from the oxygen sensor control before the catalytic converter. Oxygen sensor control behind catalytic converter is superior to oxygen sensor control before catalytic converter and is the primary control. It corrects slight changes in the mixture (i.e. enrichment or thinning) by holding oxygen sensor control before catalytic converter at its highest or lowest point for a specific time (duration). If this time is in the positive range (i.e. 50 ms), mixture is shifted in the -enrich- direction. If this time is in the negative range (i.e. 50 ms), mixture is shifted in the -lean- direction. After checking my fuel trims and seeing that they were all within a few percent, I once again disregarded it. A few months ago I threw a secondary O2 Sensor heater code which activated my CEL. This prompted me to code out my secondary O2's. Recently, my CEL came back on, primary O2 sensor this time. So I did what any responsible Audi owner would do and replaced both primary sensors immediately. I did this thinking that it would solve all of my problems. It didn't. Approximately three hundred miles later, remembering my suspicious P1176 research, I unplugged my secondary O2's as a last effort. Almost immediately, my part throttle power improved immensely. I was searching through the Funktionsrahmen keyword "Hinter Kat" and had some promising hits, however, I recentely moved and don't currently have the internet on my laptop. Could this have just been a result of adaptation slowly taking effect after replacing my primary O2 sensors? Has anyone found any maps relating to secondary O2 correction? Has anyone come across anything related to post cat correction in the Funktionsrahmen? Title: Re: Post Cat Correction - 2001 Audi S4 Post by: coreyj03 on April 12, 2011, 10:09:57 PM so can we just code the secondary o2 out so they dont throw a CEL and un plug the rear o2's.
i have a heater circuit code for a secondary o2 and i have also intermittent loss of power in off boost conditions. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on April 13, 2011, 10:20:35 PM Yes, I just coded them out and unplugged them. Problem solved, no CEL, and readiness is set.
Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on April 16, 2011, 02:12:05 PM I would love to hear some feedback, insight, opinions on this.
Just a quick dash through the G box OLS, it looks like module LRSHK controls post cat O2 correction. I have not looked at it in detail yet though. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: vwaudiguy on April 19, 2011, 11:55:41 AM I believe the second 02's are there as well for more than just cat monitoring. I had a friend (vw tech) have a problem with his 1.8t golf dumping fuel, and after changing the second 02 problem resolved. It was so long ago he doesn't remember the exact details like fuel trims, etc. I always keep this example in the back of my head when trying to troubleshoot problems..Maybe this isn't a good thing? :)
Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on April 20, 2011, 01:17:46 AM I found a little more information looking through the funktionsrahmen tonight. I also think that I found the codeword to disable post cat correction.
Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on April 20, 2011, 01:22:01 AM Quote from: Funktionsrahmen The regulation by the probe behind Kat is the lambda control with the probe before the catalytic converter by way of superimposed. Control action on the legislation before the catalytic converter, the Delta Lambda Korrekturgr variables dlahi_w and dlahp_w. Control is post Cat: Can be disabled by setting Bit 0 in code word CLRSHK to 1 (FALSE). Effective regulation P-/I-: The regulation behind Kat is a regulation by integral / proportional action. The P-share dlahp_w immediately, because he does not have "memory ", after changing the sensor voltage with the correct sign with respect to the control position by the delta-lambda-through enriched or lean. Through the integral component of the regulation behind the catalytic converter is LRSHK capable of exhaust deterioration caused by a shift the static probe characteristic can be caused to compensate to a large extent. The calculation of LRSHK is continuous on lambda level. For this purpose, first the probe voltage ushk_w by way of the Characteristic LALIUSH (lamsonh_w) linearization. A similar linearization with the voltage set point USRHK made (lamsolh_w). The pseudo-feedback is lamsonh_w project specific operates by way of code word CLRSHK resold. a) directly, (-> default in Modulating Before regulation cat, as intervention all is possible 10ms) b) filtered by way of a PT1-element (-> project-specific) c) fr-synchronously averaged (-> default for two-point control, since depends only before tv fr-jump prospective is) as a rule lamhm_w subtraction dlashkm_w are fed. By assessing the characteristics of and KDLASHKP KDLASHKI, the control difference dlashkm_w will be corrected separately according to the catalyst properties before the calculation of the P and I_ proportion. The distorted or control differences dlashkp_w dlashki_w result now by weighting by KPLRHML = f (ml) of the P-proportion dlahp_w, or by weighting by KILRHML = f (ml) of the I-proportion dlahi_w. Code word CLRSHK ---------------- To w application during the treatment of the adaptation value dlahi_w bein k it is possible to influence, has the code word CLRSHK inserted leads. The meaning of the control bits in CLRSHK are described in the block comments. Useful combinations - in decimal - are listed following leads: CLRSHK = disabled is odd LRSHK CLRSHK = 16 dlahi_w resetting erasure is at fault memory l with the value DLAHIINI otherwise default state for LRSHK CLRSHK = 24 dlahi_w is resetting during engine start with the value DLAHIINI Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on April 20, 2011, 01:24:21 AM 0x11A87 CLRSHK Code word for Lambda - Control post Kat on/off (original value 72) set to odd?
0x19FCF CLRSHKA Code word for Lambda - Control post Kat (original value 0) set to 1? Title: Re: Post Cat Correction - 2001 Audi S4 Post by: nyet on April 20, 2011, 09:49:19 AM 0x11A87 CLRSHK Code word for Lambda - Control post Kat on/off (original value 72) set to odd? 0x19FCF CLRSHKA Code word for Lambda - Control post Kat (original value 0) set to 1? Sounds reasonable. Added to tuning wiki. However, in some DAMOS they may be CLRHK and CLRKHA? Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on April 23, 2011, 12:55:42 AM I have attached the full (except schematics) LRSHK module translated to English.
Title: Re: Post Cat Correction - 2001 Audi S4 Post by: nyet on May 12, 2011, 10:15:14 AM 0x11A87 CLRSHK Code word for Lambda - Control post Kat on/off (original value 72) set to odd? 0x19FCF CLRSHKA Code word for Lambda - Control post Kat (original value 0) set to 1? Added to latest map pack http://www.nefariousmotorsports.com/forum/index.php/topic,200.msg4966.html#msg4966 Title: Re: Post Cat Correction - 2001 Audi S4 Post by: Tony@NefMoto on May 12, 2011, 11:04:38 AM In my testing I did not find that the post cat O2 sensors made a difference if they were connected or not. I only tested with working O2 sensors though, so it is possible they help when one or more of the O2 sensors is failing.
In my car I completely disconnected the rear O2 sensors. Then I disabled the cat efficiency code, and the codes for the rear O2 heaters. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: Capt. Obvious on May 17, 2011, 10:29:56 AM In my testing I did not find that the post cat O2 sensors made a difference if they were connected or not. I only tested with working O2 sensors though, so it is possible they help when one or more of the O2 sensors is failing. This is exactly what I did in my car. No problems after several hundred miles of driving.In my car I completely disconnected the rear O2 sensors. Then I disabled the cat efficiency code, and the codes for the rear O2 heaters. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on May 17, 2011, 12:00:46 PM In my testing I did not find that the post cat O2 sensors made a difference if they were connected or not. I only tested with working O2 sensors though, so it is possible they help when one or more of the O2 sensors is failing. This is exactly what I did in my car. No problems after several hundred miles of driving.In my car I completely disconnected the rear O2 sensors. Then I disabled the cat efficiency code, and the codes for the rear O2 heaters. Yes, that is what corrected my problem. Code out and uplugged sensors. I plan to play around with disabling correction when I get the chance. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on May 22, 2011, 01:39:34 AM Messing around with VCDS tonight I decided to check my secondary O2 sensor readings. With the sensors unplugged, the readings oscillated from 0.435v to 0.43v. I believe this to be ~Lambda 1.
I then plugged them in and of course the readings are all over the place. The average voltage bank 1 was 0.274, while bank 2 averaged 0.9 volts. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: gremlin on May 22, 2011, 02:48:25 AM The best way to resolve question "how to do".
I think with technology used by ... ECU manufacturer. We can do that after analyze of 2 stock files of 1.8T engines One for engine ANB (Euro3, post-cat O2S, secondary air) Another for APU, fully ANB clone but without 2-nd sensor and SA. Just compare binaries... Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on January 07, 2012, 12:29:44 PM I took another real quick look at this after rob.mwpropane asked about it. I found some possible errors in my interpretation of the codewords.
I only see CLRHKA referenced once where set to one switches from tkatm (cat temp model) to tikatm (EGT in cat model). Not very interesting. CLRHK bit zero set (1) disables post cat lambda regulation by assigning tvlrh and tvlrhi equals zero. I haven't gone through the other bits of CLRHK yet to see if atv needs to be manipulated or not. This may be used to exclude the post cat O2 sensors from the pre cat aging tests. Original value for CLRHK is 72 (bits 3 and 6 set) so setting it to 73 (set bit 0) will maintain stock configuration and disable lambda regulation. If I get some time I will try to readdress this. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on January 09, 2012, 12:32:56 AM I took another quick look at CLRHK today.
It looks like the best combination is bits zero and two, CLRHK=5. You do not want to set bits 1 and 3. Bits 4-7 are have no effect if bit zero is set. ATV is initialized to zero at startup with bit 2 set. CLRHKA may actually be the key though. Basically the whole function is shutdown if tkatm (cat temp model) or tikatm (EGT in cat model) can be kept below 300 degrees celcius (TKATMLRH). Title: Re: Post Cat Correction - 2001 Audi S4 Post by: nyet on January 09, 2012, 12:34:48 AM phila... thanks for your work. Let me know when you have some recommendations for the s4wiki :)
Title: Re: Post Cat Correction - 2001 Audi S4 Post by: rob.mwpropane on January 09, 2012, 04:01:45 AM I took another quick look at CLRHK today.
It looks like the best combination is bits zero and two, CLRHK=5. You do not want to set bits 1 and 3. Bits 4-7 are have no effect if bit zero is set. ATV is initialized to zero at startup with bit 2 set. CLRHKA may actually be the key though. Basically the whole function is shutdown if tkatm (cat temp model) or tikatm (EGT in cat model) can be kept below 300 degrees celcius (TKATMLRH). Wow, good work. Thank you very much for having another look. I wasn't sure if what I was working out was correct or not. Thanks! Title: Re: Post Cat Correction - 2001 Audi S4 Post by: masterj on January 09, 2012, 07:04:01 AM And that is why my front o2 sensor can't pass aging test and also limp mode... :(
BTW: Could someone confirm me 100% that CRLHK is @ 12122 and CLRHKA is @ 1A1AF (bin attached) ? Because I've set CRLHK to 5 and CLRHKA to 1 but there's no effect. Front O2 sensor still can't finish aging test... Title: Re: Post Cat Correction - 2001 Audi S4 Post by: TTQS on January 09, 2012, 09:05:42 AM LRSHK 9.20 (Continuous Post-Catalyst Lambda Control) translation added to Nefmoto wiki.
TTQS Title: Re: Post Cat Correction - 2001 Audi S4 Post by: masterj on January 11, 2012, 11:56:40 AM LRSHK 9.20 (Continuous Post-Catalyst Lambda Control) translation added to Nefmoto wiki. TTQS Great!!! Gonna take a look :) Title: Re: Post Cat Correction - 2001 Audi S4 Post by: cactusgreens4 on February 13, 2012, 12:28:14 PM Are the primary, aka first in line, o2 sensors needed or are they also coded out when doing piggie pipes?
Title: Re: Post Cat Correction - 2001 Audi S4 Post by: nyet on February 13, 2012, 12:40:07 PM so is 5 preferred to 73? any update on this?
TIA :) Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on February 13, 2012, 02:32:29 PM Are the primary, aka first in line, o2 sensors needed or are they also coded out when doing piggie pipes? You definitely do not want to code out your primary O2's for piggie pipes. so is 5 preferred to 73? any update on this? TIA :) Theoretically, CLRHK = 5. I haven't done conclusive testing yet. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: nyet on February 13, 2012, 02:36:00 PM The only significant difference between 5 and 73 seems to be bit 3?
Title: Re: Post Cat Correction - 2001 Audi S4 Post by: cactusgreens4 on February 13, 2012, 07:48:17 PM You definitely do not want to code out your primary O2's for piggie pipes. So the ones that have been coded out are probably the rear ones and i need to hook the ones right after the turbo back up again? Thanks for clearing this up for me... now all I have to figure out is what to do about the main cats... Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on February 15, 2012, 12:01:30 AM The only significant difference between 5 and 73 seems to be bit 3? Yes because setting bit 0 makes bit 6 insignificant. Bit 3 = 0 should help with primary O2 sensor aging tests, but CDLATV = 0 appears to be a better way to neutralize ATV completely. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: masterj on February 15, 2012, 11:01:00 AM Yes because setting bit 0 makes bit 6 insignificant. Bit 3 = 0 should help with primary O2 sensor aging tests, but CDLATV = 0 appears to be a better way to neutralize ATV completely. In my file setting CLRHK to 5 and CLRHKA to 1 doesn't help with precat aging tests... Maybe I defined them incorrectly? Right now I defined those maps at 12122 and 1a14f.... Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on February 15, 2012, 11:56:50 AM You could try CDLATV=0. I haven't looked through it completely, but it should remove post cat O2's completely from O2 sensor aging tests.
Title: Re: Post Cat Correction - 2001 Audi S4 Post by: nyet on February 15, 2012, 12:10:52 PM I'm not sure I understand... I don't have CLATV set to zero, but my o2s are removed and everything is fine.
is this because I'm using 73 and not 5? Title: Re: Post Cat Correction - 2001 Audi S4 Post by: masterj on February 15, 2012, 12:24:23 PM You could try CDLATV=0. I haven't looked through it completely, but it should remove post cat O2's completely from O2 sensor aging tests. Ofcourse if I disable aging mixture test (CDLATV=0) then I can pass readliness (same as zeroeing all the tests - makes them passed in vcds), but this is bad solution, because, then you'll never know if your front o2 sensor is bad or not. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on February 15, 2012, 12:39:54 PM Ofcourse if I disable aging mixture test (CDLATV=0) then I can pass readliness (same as zeroeing all the tests - makes them passed in vcds), but this is bad solution, because, then you'll never know if your front o2 sensor is bad or not. I haven't looked into it completely, but it was my understanding that CDLATV only affected if the rear sensors were considered in the primary O2 aging test. Title: Re: Post Cat Correction - 2001 Audi S4 Post by: masterj on February 15, 2012, 12:44:39 PM I haven't looked into it completely, but it was my understanding that CDLATV only affected if the rear sensors were considered in the primary O2 aging test. That is not what I found out... CDLATV and CDLATP both are aging tests for front sensor. CDLATV is "Mixture Test" and CDLATP is "Two-Point Control Test". If you zero out CDLATV you're zeroing half of the aging test... Title: Re: Post Cat Correction - 2001 Audi S4 Post by: phila_dot on February 15, 2012, 02:35:59 PM That is not what I found out... CDLATV and CDLATP both are aging tests for front sensor. CDLATV is "Mixture Test" and CDLATP is "Two-Point Control Test". If you zero out CDLATV you're zeroing half of the aging test... ATV monitoring is evaluating mixture control based on post cat O2 sensor readings. atv is calculated in LRHK. With post cat O2 sensors removed or faulty you will not want to utilize the sensor voltage in this test. My final conclusion without confirmation from logging is CLRHK=5 and CDLATV=0. |