An update campaign for T6 EU6 diesel engines took place in 2019-20. Affected engines were on van of model years MY16-MY18, including some of MY19.
For M1 class (passenger carriers, VIN WV2...) the update was an official recall.
For N1 class (VIN WV1....) the update was not classified as mandatory but was/will be done if faults (especially P204F, P20EE) show up. So basically the decision is left to service center.
In the paperwork it was mentioned that the update might increase AdBlue consumption slightly - as a compensation free AdBlue fill-ups were offered.
T6s used in the evaluation - MY18 DSG 4Motion
Engine from factory:
CXEB 04L 906 056 KN version 3776 - EU6 150kW/204PS
After the update the engine is identified as:
CXEB 04L 997 264 B version 9542
Test journeys
The pictures below are about same type of journey - 30 kilometers, 30 minutes. About half of that on country road 80 km/h, the rest through villages 50-60 km/h. For the speed see the black curves.
NOx emissions [ppm] in green as reported by van's own NOx sensor. Reported AdBlue-consumption [mg/s] in blue.
The journeys shown here were recorded in May-June in 2019 (before update), and respectively after the update in April-June 2020.
Part 1 - Before Engine Software Update
Picture 1 - normal engine run
In summary for this journey 28.97 grams of AdBlue was consumed (as reported by Engine Controller Unit)
For future reference please note that NOx sensor needs to heat up to activate - here the activation happens at 721 seconds from start - till then the sensor reports plain zero.
Picture 2 - engine performing DPF regeneration during the journey
In summary for this journey 14.81 grams of AdBlue was consumed.
Worth noting
(1) NOx sensor wakes up alredy at 450 seconds thanks to hot exhaust gases of DPF regeneration
(2) No AdBlue injection during DPF regeneration (blue curve)
Full scale picture of NOx emissions below in spoiler
Basically just pictures 1-4 above converted to dull numbers
All the runs were as identical as possible along other traffic - same route, thus same uphills/downhills, stops, etc. Average speed about 60 km/h.
NOx sensor readings are average over only over sensor's active period - otherwise the values would be too "diluted" by initial inactivity.
Also worth to note that DPF regeneration didn't last full journey - thus the values are a bit diluted by non-regen time - approx. 10 minutes from end. Also might be of interest that DPF regen was due when setting off thus maximum heat-up from cold engine (+10..+15C)
Well, jumping into conclusions based on just one set of measurements:
Typically, using the driving profile above a full DPF regeneration cycle would consist of
7 x normal engine runs (each 30 km)
1 x DPF regeneration during the journey (each 30 km)
thus AdBlue consumed would have been
BEFORE the update: 7 x 29.0 grams + 1 x 14.8 grams = TOTAL 218 grams
AFTER the update: 7 x 37.7 grams + 1 x 107.8 grams = TOTAL 372 grams
The numbers interestingly show an increase of approx. 70% in AdBLue consumption thanks to the ECU update
Not scientifically accurate but a kind of pinpoints where the culprit for the increased consumption is.
Certainly should have taken into account now (after update) less frequent DPF regenerations (see part 4), which actually worsens the numbers a bit.
Conclusions about short term statistics
(1) For normal engine run - by the ECU update NOx emission were reduced by 16% However the AdBlue consumption did increase by 30%.
(2) For the DPF regeneration the numbers are quite drastic. The update reduced NOx emissions by 80%. However, for this journey 7.3 times more AdBlue was consumed - mainly because before the ECU update, no AdBlue was used during DPF regeneration.
Statistics - medium term
No pictures... unless...
Another set of statistics - for a fairly long drive - just to dilute engine cold start effects on NOx emissions - possibly addressed by ECU update (see above "Short term stats") - possibly related to infamous P20EE fault code in early days of T6.
In this data the "DPF regeneration" period has been isolated from the data (different journeys than "Normal engine run" here) - also the DPF regen started on route when engine had been up to normal operating temperature for a while already - thus slightly different case than in short term stats
Conclusions about medium term statistics
(1) For normal engine run - the NOx emission seem to be unaffected by the ECU update.
(2) For the DPF regeneration - quite a difference before and after the ECU update both in NOx emissions and AdBlue consumption. Quite a significant burst of AdBlue now during the DPF regen. Not to mention about extra squirt of diesel...
Statistics - long term
Brim-to-brim AdBlue fill-ups were noted down before and after the ECU update. 19 months before, and 24 months after the ECU update
0.73 litres/1000 km = 3880 mpg
1.25 litres/1000 km = 2260 mpg
Conclusions about long term statistics
Indeed, there was a slight increase in AdBlue consumption....
However, there seems to be a change also in fuel consumption, too - e.g. see Part 4 "Distribution of distance travelled between DPF regenerations"
Interestingly full fuel consumption statistics indicate that the above mentioned 0.52 litre "loss" of AdBlue over 1000 km has been compensated by reduced fuel consumption of 2.1 litres over the same 1000 km distance. Not a bad deal it seems...
The numbers about fuel usage were collected over
34383 km and 23 months - before the ECU update
35692 km and 27 months - after the ECU update
Partially can be explained by less frequent DPF regenerations... some numbers about that
In March 2020 finally got the long-awaited ECU (Engine Control Unit) software update. Unfortunately it took a while to get a good chance to do some measurements to try to figure out what has been changed. So finally a few weeks back dusted the VCDS and collected all kind of intriguing data. The...
www.t6forum.com
Perhpas just another effect of global warming, me getting older,... , VW's good will perhaps
Part 4 - Other observed changes with the ECU update
Relaxed soot accumulation limits for DPF regeneration
Before update DPF regeneration was initiated at soot level (calculated) of 24.0 grams. The DPF regeneration was finished when soot level (calculated) was reduced down to 6.0 grams. By taking advantage of still hot exhaust gases the soot level could go even as low as approx. 5 grams - because of so called passive regeneration.
For the updated ECU software the limits are respectively 30 grams and 9 grams - thus approx. 17% more "space" for soot (21 grams vs. 18 grams before). This should manifest itself as less frequent DPF regenerations.
DPF regeneration thresholding
The engine software (04L906056KQ/3775 = before the update) has an interesting feature re DPF regenerations. Most likely the feature is also on other engines.
If engine is turned off when DPF regen has reached more than (approx.) 75% the full regen cycle (that is - soot calculated is below 11 grams (of full cycle from 24 grams down to 6 grams), the DPF regeneration does not continue any more when engine is restarted next time.
Instead engine runs normally till soot level reaches again 24 grams. Thus this next DPF regen sometimes seems to come fairly soon after the last (actually only partial) DPF regeneration. This shortened cycle combined with highly elevated NOx levels during DPF regeneration could be a candidate for P20EE fault under certain conditions.
Exact threshold TBC - highest recorded soot calculated was 10.61 grams, which ECU considered as finished DPF regeneration.
Worth noting the updated software doesn't have this "thresholding" anymore. Even remaining less than 0.5 grams soot to burn off, the regen is started again for a few minutes to fully clear the soot counter. A kind of unnecessary exhaust heat-up... IMO
DPF regeneration when FUEL LOW (dash light)
Before update the engine (04L906056KQ/3775) didn't start DPF regeneration when FUEL LOW dash light was on.
Forum members have reported that with updated ECU software DPF regeneration will commence even in FUEL LOW condition.
EDIT (2024-05-17): Finally the conditions were right to verify - fuel low warning light turned on at soot (calculated) level 29.6 grams thus the DPF regen should have started approx. 4 minutes later at 30.0 grams of soot - the DPF REGEN DID NOT START while fuel low warning. Finished the journey 20 minutes later at 31.9 grams of soot (calculated) - without DPF regeneration.
DPF regeneration etc. was monitored using Android Torque app with T6 specific PID set
Here's another approach for T6 DIY enthusiasts - taking advantage of very popular Carista OBDII-reader device - combined with an Android app. Ingredients: T6 EU6 engine: CXEB,CXEC,CXFA,CXGA,CXGB,CXGC,CXHA,CXHB. Carista OBDII device (also other generic OBDII (ELM327) devices will work) for...
Forgive me if I’m wrong But with a 70% increase in adblue can those that have the T6 models asked for a bigger adblue tank that the T6.1 vehicles have.
Without a VCDS can I tell if I’ve been updated ( All my services are completed by VW ) and does this mean we my have to carry a certificate or sticker to meet some EU countries clean air zones
is this the start of another dieselgate
Forgive me if I’m wrong But with a 70% increase in adblue can those that have the T6 models asked for a bigger adblue tank that the T6.1 vehicles have.
On my van after filling up the AdBlue the counter still reports the same 9000 km (5500 miles) remaining range as before. In spite of increased consumption I still get 11000 km (7000 miles) out of the tank. Can't complain although before the update got 20000 km per tank (12500 miles).
Besides VCDS there are other tools: Carista, OBDeleven even some free tools (e.g. VAG DPF) can extract the version information.
However, to find what's the latest suitable version might be a bit more challenging. E.g. this site usually gives some clues -
Not yet- actually for T6 with VIN WV1... also the original ECU software fulfills the requirements - says VW.
However, in not so distant future there will be a change in EU. Some of the legislation has already been adapted for verification of emission regulations - as already effective in California.
Just came across this super interesting post/insight into how the Adblue system works and what the update changes - thanks mmi!
I happen to get both of the fault codes every few thousand miles on my T6 so guessing I could do with the update. I asked Vindis Van centre about it and they quoted the below:
Is this reasonable? I'm not sure how Odis? works but will they sort of bulk update all the modules to apply this update or just the Adblue system? If the former it kind for feels like better value!
I'm not sure how Odis? works but will they sort of bulk update all the modules to apply this update or just the Adblue system? If the former it kind for feels like better value!
Hello again knowledgeable people,
I read the top post with interest as I have had both fault codes diagnosed this morning (P20EE) and (P204F). The garage, (not a VW specialist) said the 1st port of call was a software update.
I rang VW in Beeston, Notts who said they would have to plug it in and couldn't comment. When I asked if he would put my registration in his system to check for updates/recalls he did so. His answer - nothing outstanding!
How does one get this update?
Thanks.
My understanding after being through the same discussions is that it's a software update VW fitters will apply as the solution to those particular error codes if you pay them to plug it in and for the time to apply the fix/update. It's not a mandatory update/recall as such and therefore won't be flagged to them through a simple phone call/vin check.
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- e.g. see Part 4 "Distribution of distance travelled between DPF regenerations"
