Lambda aging tests

[Breezy_Pete]

Any experts out there who know how to do these lambda sensor aging tests, or is it self-explanatory once you get into the right bits of VCDS?

 

I've only recently got my car(s) plugged in and I really don't know my way around VCDS yet. I think I've read that these tests (and cat efficiency test) are in Basic Settings? I've got a Gendan cable that's appropriate and connects OK, and the 99USD licensed version of Lite.  I'm not very brave with it all yet, so any guidance/assistance would be much appreciated.

 

The two cars/engines I'd be interested in running the tests on are a 05 Fabia with AZQ engine, and a 53 Polo with BBY engine.  Both have wideband precat and normal postcat sensors.

 

There isn't/aren't any fault codes relevant to these things, but the HCs were a little high at the Polo's recent MOT, 100ppm or so. That's only half the limit; but the Fabia's number is much lower (single figures, virtually, I seem to remember). Wondered if I could pre-empt a problem by running some tests.

 

Cheers for any steers.

 

 

[James@RRG_Skoda_Rochdale]

The bby has an extra cylinder worth of emissions pal, I think you're stabbing in the dark.

bby 1.4 16v

azq 1.2 12v

[Breezy_Pete]

Err, thanks for that. V. helpful.

[James@RRG_Skoda_Rochdale]

Well if you want to have a mess and waste your time doing what your rather clever Siemens and magnetti marrelli ecu's will tell you in the event of a fault on the emissions cycle you can read blocks 1,2 and 3 from cold which should contain engine speed, temp, and lambda voltage.

as the temp reaches its correct operating temperature (circa 85-100 degrees Celsius) the lambda should remain but fluctuate around 1.0v. positive deviation signifys lean running (normal on warm up) negative shows rich running.

[Breezy_Pete]

If you don't know anything about the lambda aging tests, your input here is rather wasted.

[James@RRG_Skoda_Rochdale]

I've just given you a basic how to in my previous post.

[James@RRG_Skoda_Rochdale]

Some useful info on fuel trims here:

http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info

and data blocks here:

http://www.ross-tech.com/vag-com/m_blocks/030-049.html

a little gratitude wouldn't go a miss either, seeing as though I'm the only person attempting to assist you.

[James@RRG_Skoda_Rochdale]

Some other useful info including a more thorough guide:

CHECKING THE LAMBDA PROBE AGEING

Select “Group” and enter the value 030, Click “GO” or press the Enter key or on some cars, click on “ON/OFF/Next” box in upper right of the display

Check the operating state of lambda control display fields 1 and 2

Specified value display field 1: 111

Specified value display field 2: 110

Note, this may take a few minutes at idle or even require the rpm to be raised to around 2500>2800rpm for a minute or so

The first position in the 3-digit numerical block fluctuates initially between 0 and 1 (lambda probe heater off and on)

The lambda control of lambda probe downstream of catalyst is not active without engine load and the third position in display field 2 indicates 0

AGEING TEST OF THE LAMBDA PROBE BEFORE CATALYST

Select “Group” and enter the value 034, Click “GO” or press the Enter key or on some cars, click on “ON/OFF/Next” box in upper right of the display

Depress the brake pedal and accelerator simultaneously, some engines only require the brake pedal to be depressed

Engine speed is increased and set by the ECU and the readout in display field 4 switches from “Test OFF” to “Test ON”

Catalytic converter temperature in display field 2 must be at least350 °C. This may take a few minutes

Run the engine until display field 4 indicates specified value “B1-S1 O.K.”

CHECKING LAMBDA PROBE PREPARATION DOWNSTREAM OFCATALYTIC CONVERTER

Select “Group” and enter the value 036, Click “GO” or press the Enter key or on some cars, click on “ON/OFF/Next” box in upper right of the display

Depress the brake pedal and accelerator simultaneously, some engines only require the brake pedal to be depressed

Engine speed is increased and set by the ECU, the display in display field 4 will then switch from “Test OFF” to “Test ON”

Run the engine until display field 4 indicates specified value “B1-S2 O.K.”

DIAGNOSIS OF LAMBDA CONTROL SYSTEM

Select “Group” and enter the value 037, Click “GO” or press the Enter key or on some cars, click on “ON/OFF/Next” box in upper right of the display

Depress brake pedal and accelerator simultaneously, some engines only require the brake pedal to be depressed

Engine speed is increased and set by the ECU, the display in display field 4 will then switch from “Test OFF” to “Test ON”

Run the engine until field 4 indicates specified value “System OK.”

AGEING TEST OF LAMBDA PROBE AFTER CATALYST

Select “Group” and enter the value 043, Click “GO” or press the Enter key or on some cars, click on “ON/OFF/Next” box in upper right of the display

Depress brake pedal and accelerator simultaneously, some engines only require the brake pedal to be depressed

Engine speed is increased and set by the ECU and the readout in display field 4 switches from “Test OFF” to “Test ON”

Continue running engine at higher speed until the catalytic convertertemperature in display field 2 shows at least 200 °C. This may take a few minutes

Run the engine until display field 4 changes from “TEST OFF” to “TEST ON” and then to the “B1-S2 O.K.”

CATALYST DIAGNOSIS

Select “Group” and enter the value 046, Click “GO” or press the Enter key or on some cars, click on “ON/OFF/Next” box in upper right of the display

Depress brake pedal and accelerator simultaneously, some engines only require the brake pedal to be depressed

Engine speed is increased and set by the ECU and the readout in display field 4 switches from “Test OFF” to “Test ON” but on some engines the throttle has to be held to set speed to 2500...4500 rpm

Catalytic converter temperature in display field 2 must be at least400 °C and this may take a few minutes

When the readout in display field 4 should changes from “Test OFF” to “Test ON”, maintain the speed until the readout in display field 4 shows the specified value “CatB1 O.K.”

[Breezy_Pete]

Thanks for your interest.

I'll select blocks 34, 36, 37 in basic settings and the other two.

Anyone actually done these tests, on any engine?

[Breezy_Pete]

Almost simultaneous posting now, thanks, that latest does look very useful.

[James@RRG_Skoda_Rochdale]

i've carried out the guided test plan on dealer software lots of times, sadly it doesn't tell you exactly what it blocks it's monitoring and literally gives you a pass or fail result in the end for each component.

There are cheap handheld scanner with a readiness test built in to them to conform with the eobd regulations.

I don't want to go off on a tangent here and know they're not easily accessed but an emissions tester is just about the best piece of equipment to test the system.

[James@RRG_Skoda_Rochdale]

Almost simultaneous posting now, thanks, that latest does look very useful.

a bit more useful info than that which I could reap from the top of my head!

[Breezy_Pete]

So, having read your last post (#8) fully, I'm now (I hope you'll be mollified to hear) tending to wonder "is there any point to these tests?" Forgive me for not knowing this ahead of time, but I assumed (hehe) that they might supply some more detailed diagnostic info than it seems they actually do. From your above info, it looks like all these tests are binary, pass-fail, rather than what I was imagining. So it does indeed seem a bit futile to run them, because if the result was 'fail', the ECU should already have flagged up a fault. Maybe they are a useful double-check? Maybe they eliminate some possible confounding causes for fault codes?

 

Am I missing something, or is that an accurate picture? I was imagining that they might somehow say something like "precat sensor getting a bit long-in-the-tooth, consider replacing it within the next 20k miles", or words to that effect.    

 

Apologies for my initial reaction to your early posts.

[James@RRG_Skoda_Rochdale]

lambda and catalyst diagnosis can either be very easy or very difficult. when you carry out these tests you are just watching 1 cycle of what the ecu monitors many times when the car is in use. lambda faults on both the engine codes you have mentioned are common place and some can fail the rediness tests yet won't flag fault codes.

having toiled with them myself in the past I find the best and most definitive manner of testing is a fault code scan then watch the live data whilst running the car on an emissions tester.

[James@RRG_Skoda_Rochdale]

Don't worry about your reaction earlier. lambda testing is difficult work but usually best monitored with regular fault code scans unless you fancy getting to grips with an oscilloscope :-s

hence my attempts to make you try different things first or leave them until a light pops up on the dash.

[Breezy_Pete]

Just found a very interesting post from a 4-page thread in the Octavia 1 section from 5 or 6 years back.  This is the post that encourages me that I might not be completely wasting my time here. This is the link for the whole thread, but at a quick glance, there's not much else of relevance.

 

Some snippets from the post:

 

(About block 34 test) "aging value must be above 0.80. The value for a new sensor is 1.99. The value will decrease as the sensor ages"

(About block 46 test) "Field 3 is the cat. conversion efficiency. If the cat is good, the value should be below 0.50 at the end of the test"

 

So it looks like there is some analogue data, which is kinda what I was hoping for.

 

I'm encouraged to get involved tomorrow, and see what I can see. :sun:

[Breezy_Pete]

I made a bit of progress on this when I got home from work.

 

First observation is that there is nothing in the way of guidance on screen about how to initiate these tests, nor about any pre-requisites prior to doing so.

 

Of the 3 I tried in basic settings; blocks 34, 36, 46, the only one I could get to do the test was 36, the downstream lambda, which I triggered by just touching the brake pedal after clicking Go.

It very briefly raised the engine revs, then almost immediately clicked over to saying B1 S2 OK, which was encouraging.

 

Whatever I tried with brake pedal and/or accelerator pedal, I couldn't get tests 34 or 46 to run.

 

As luck would have it, I've now found some details specific to the relevant 1.4/16v engines of how to initiate these others (e.g. for 34, blip throttle twice above 5k rpm, then hold above 1500 until test starts).  so I should be able to make more progress tomorrow.  Only thing is, the info I've found doesn't mention those continuous values that are mentioned in the Octavia thread, so I'm not sure whether I'll see them or not.

[Breezy_Pete]

Well, today I got all these tests to run, but the results - other than everything passing - don't really offer me any information that is much use, without further explanation.

 

The ageing test for the pre-cat wideband lambda (34 in basic settings) was initiated as in the post above, except that the revs had to be held around 2000 to start the test, and held there to keep it going.  (And coolant had to be >80C).

In the instructions I found, it suggested that once the last field switched from Test OFF to Test ON, you should let the revs drop back to idle, but this just resulted in it immediately switching back to Test OFF. Holding the revs above about 2000 kept the test going until it concluded with the result B1 S1 OK and a time in seconds in the third field which I think was 0.6, but I didn't write it down at the time. No idea whether that's a good number or not, and no obvious way of finding out. So that wasn't a roaring success. 

 

The Catalyst diagnosis test, group 46 in basic settings, wasn't a lot more informative.  The four fields you see here are rpm, cat temp, 'Amplitude behaviour' and Test status.

To initiate, you get the cat temp reading above 300C (by revving engine), and hold rpm above 2000 for a bit, and you get Test OFF turning to Test ON in the fourth field.  After a short while of holding the revs up above 2000ish, you get a result in the fourth field,  Cat B1 OK, and a percentage figure in the third column, in this case 99.6%.  What a 99.6% figure for 'amplitude behaviour' means is sadly a little opaque to me.  If anyone knows what it means I'd be happy to have it clarified.   Sounds better than 30% anyway, somehow.

 

So all-in-all, I have to conclude that therevrendjr was basically correct; unless you have a source of info on how to interpret the third-field numbers from each of these tests, there's not a lot to be learned other than that each item is OK, or not: but you'd likely already know that if the answer was not, from a fault code being lobbed out at you.

 

Reassured, but mildly disappointed. Time for a drop more red.

[James@RRG_Skoda_Rochdale]

That's just how it is with diagnostic technology. you can check and check something and the result is always so vague you end up no wiser than when you started.

[Breezy_Pete]

I'm pretty sure I have sufficient info to do the same tests on the Fabia (the above were all on the Polo), if the missus'll let me some time.

At least I might get some comparative data that way, if the third field seems to be the same measurement in both cases.

 

Thanks again for your interest and advice. :sun: