My 2001 A6 2.7 tiptronic with 140,000 miles has been giving the 16805 code warm up catalyst bank 1 and p0421 efficiency below threshold. If I clear it, it returns within 50 miles.

Normally it is the only code I get when I look for DTC codes. "jcman" suggested in another post that before jumping to the conclusion the cat is bad to run a readiness test . I ran this test and all passed except for "Secondary Air Injection: failed or Incomplete.

Then received a 17519 Oxygen sensor regulation: bank 1 P1111 35-00 system too lean.

Is this telling me the rear bank 1 oxygen sensor it kaput?

Also, how do I test the Secondary Air pump? I once had a tech at my indy do something with his VAG COM to temporarily turn on the pump,as a test. How do I do this? Could this be the reason or cause for these other codes 16805 and 17519?

Thanks

 

With the other tests, the "Holy Grail of Vag-Com"
Good Luck!

 

I thought that is what I just did. The readiness test. It came back with all passing except the secondary air injection.

I just tried running the test on the air injection pump and it ran but made a lot of noise,surging and groaning. Is it correct to assume this may be the cause of the other trouble codes??? Repair this first and see? Is that the most likely order?

 

Are you doing the test when the engine is at idle?

 

Using this page of the pdf?

 

The secondary pump test was done at idle.

I was going to do the readiness test per the document you referenced but instead I found a readiness test button on the VCDS screen and ran that one. It was pretty much the same but with 32 steps. Some were intermediate steps like bring engine up to 2000 rpm +/- or let engine resume idle and stabilize.

When I did this test a second time after driving the car 30 miles then all sections passed, but it still displayed
17519 - Oxygen (Lambda) Sensor Regulation: Bank 1
P1111 - 35-00 - System too Lean

Then I ran another test and got the following
Address 01: DTCs clearedSaturday,07,April,2012,14:42:09:01231
VCDS Version: Release 11.11.3
Data version: 20120401


TID 01 - Rich to lean sensor threshold voltage Test:0.435 V
TID 02 - Lean to rich sensor threshold voltage Test:0.435 V
TID 03 - Low sensor voltage for switch time calculation N/A
TID 04 - High sensor voltage for switch time calculation N/A
TID 05 - Rich to lean sensor switch time N/A
TID 06 - Lean to rich sensor switch time N/A
TID 07 - Minimum sensor voltage for test cycle Test:0.195 V - Min:0.000 V - Max:0.385 V
TID 08 - Maximum sensor voltage for test cycle Test:0.675 V - Min:0.480 V - Max:1.005 V
TID 09 - Time between sensor transitions Test:0.000 s - Min:0.080 s - Max:1.280 s
TID 10 - Sensor period N/A


I then drove the car back the 30 miles and got the 16805 Warm Up Catalyst Efficiency Below Threshold Bank 1 Warm Up Catalyst code again.

I know I have a problem, but do not yet know what is the cause. I am leaning to the rear oxygen sensor. I believe it is original. I just object to throwing parts at a problem, preferring to positively identify the problem.

Needless to say I am confused. Any suggestions or knowledge on this would be sincerely appreciated.

 

I haven't studied this specific test in detail, but the results you posted lead me to a couple of possible conclusions:

Note that the TID 09 line has a measured value of 0.000 sec, which is below the stated value of Min: 0.080 sec. This would tell me that the O2 sensor is never actually transitioning at all, but is staying in a perpetual lean indication. This would also follow from the initial P1111 error. If the test directly forces the engine into a rich to lean condition to check the O2 sensors (which is what I think it is doing) and the sensor only shows a lean condition, then either the engine is really too lean (doubtful since either the EGT sensors would trip, or the vehicle would drive pretty badly) or the O2 sensor is bad.

Problem there is that if the sensor is perpetually showing "lean" then why are you getting the Warm Up Catalyst error, which should come from a too rich condition during warmup (looking for a bad cat or SAI issue)? In fact people who have fooled the secondary O2 sensors with either the bung extenders or installing a diode are artificially creating the condition you seem to be seeing...

Maybe someone else (one of the Audi techs?) has a thought on this.
Jim

 

What you say makes sense. The car drives fine. What I do not understand is I thought the readiness test checks all the oxygen sensors and their functions. Is this correct? It passed all the tests on the second time I did it after running the car 30 miles. Even the secondary air injection passed. Yet, I got the failure of the same secondary air injection the day before.

Does it make sense that I have 2 issues, the rear oxygen sensor and the secondary air pump (sometimes works and sometimes only partially)? When I ran the secondary air pump test with the car off it sounded anemic, surging. Is this a valid way to test it?

 

And was the result of an intermittent SAI function that was irritating me over an 8 month period then I found a leaking combo hose vac line, I'm not an Audi tech but I can say that your results are pointing to suggesting a time reaction issues at TID 09 as mentioned by eejimm, however the warm-up phase is one that the SAI plays a substantial role in on a cold start condition and I have often wondered at certain operating temp idle conditions too.

We do know that our pre O2 sensors have one main function as to adjust fuel trim very important, the post O2 sensors report cat status with the importance of emissions only.

I would focus on the SAI system first, Bentley and Ebahn does have separate test procedures of the vac solenoid functions for the combi valves along with the combi valve diaphragm acuation with a hand-held vac pump and SAI pump test's, some have found leaks in the brittle plastic hose's, water in the pump, bad motor bearings or weak electrical connections.

 

Happy Easter!