[T6_measured] Monitoring DPF regeneration, DPF condition, EGR operation

[ebiii]

Quick update on my quest on finding what the f* is going on with my van :
Now I intermittently get a 'P0191' which is 'Fuel Rail Pressure Sensor Circuit Range/Performance'
I think it's related to my very frequent regens and quick soot buildup in the DPF. Brought it to another garage we'll see ..

 

[mmi]

'P0191' which is 'Fuel Rail Pressure Sensor Circuit Range/Performance'

First thing to check is the wiring to/from the sensor.

very frequent regens and quick soot buildup in the DPF.

Have you got any logs?

 

[ebiii]

First thing to check is the wiring to/from the sensor.

Have you got any logs?

I did not express myself correctly, I meant the soot check cycle that is not going through as pointed before. I got logs but I think it's the same as before.

The garage said the sensor went bad, and it could be a cause for dpf malfunction. I am not really believing that but we'll see

 

[ebiii]

Hi guys,

Just replaced the fuel sensor, did a little bit of analysis, it's worth what it's worth but I love doing that (raw data si attached with the variable of repair to 1 after repair and to 0 before). Here is what I find when comparing data before and after on a similar journey:

Mean values:

• For the variable "Exhaust gas temp Bank 1 Sensor 2(°C)", the mean value before the repair is approximately 260.69, and after the repair is approximately 250.38.
• The variable "T6-01 Air intake mass flow(g/s)" has a mean value of 29.29 before the repair and 28.06 after the repair.
• Similar variations can be observed for other variables as well.

What you see below is the distribution of standard deviation before and after (the mean varied slightly).
If you are stupid like me you wonder what is the red/purple bar, it's just the superposition of both data

1. Exhaust gas temp Bank 1 Sensor 2(°C): The distributions exhibit differences, especially in the higher temperature ranges.
2. T6-01 Air intake mass flow(g/s): The distributions show variations, particularly in the ranges between 10 and 20 g/s and above 40 g/s.
3. T6-01 DPF Differential pressure(mbar): The after-repair distribution tends to have higher values, especially in the range between 0 and 20 mbar.
4. T6-01 EGR Position(%): The distributions differ, especially in the lower EGR positions.
5. T6-01 Engine RPM(1/min): Both distributions appear quite similar, with only minor differences which is totally normal

Now let's do statistical analysis :

To determine whether the differences in the distributions before and after the repair are statistically significant, I'll use the Mann-Whitney U test for each variable. The Mann-Whitney U test is a non-parametric test that is used to compare two independent samples. It's especially useful when the data doesn't necessarily follow a normal distribution.

If the p-value is less than a significance level (typically 0.05), we can reject the null hypothesis and infer that there's a statistically significant difference before and after repair.

1. Exhaust gas temp Bank 1 Sensor 2(°C): The p-value is extremely close to 0, indicating a statistically significant difference before and after the repair.
2. T6-01 Air intake mass flow(g/s): The p-value is again very close to 0, suggesting a significant difference between the two groups.
3. T6-01 DPF Differential pressure(mbar): The p-value is 0.0738, which is above the typical significance threshold of 0.05. Therefore, we can't confidently say there's a significant difference for this variable.
4. T6-01 EGR Position(%): The p-value is 0, indicating a clear significant difference before and after the repair. Which I think means nothing here.
5. T6-01 Engine RPM(1/min): The p-value is 0.1114, suggesting that the difference is not statistically significant for this variable.

In the future I think I'll perform this kind of analysis on a fixed journey for exemple before and after cleaning the DPF with product 'X' and so on...

Have a nice week !

 

[ebiii]

Well my P226D disappeared after the first regen after repair of the fuel rail pressure sensor. I guess the fuel/air mix was wrong causing constant soot and as you said in earlier post, it sensor sensed constant soot going through so it generated an error. Here is today's log attached.

 

[mmi]

Well my P226D disappeared after the first regen after repair of the fuel rail pressure sensor. I guess the fuel/air mix was wrong causing constant soot and as you said in earlier post, it sensor sensed constant soot going through so it generated an error. Here is today's log attached.

Now this is interesting - the sensor is now (7.11.2023) registering less soot than before (e.g. post#66 6.8.2023 copied below) - but it still registers.





Would be interesting to see if the progress continues. Please keep us posted

 

[n10n]

Wow that’s a big difference! Very interesting!

Any other recent changes than rail pressure sensor? Different brand fuel, additives, oils or filters changed or anything like that?

 

[mmi]

Edited my post above - added in between a plot after the replacement (from data in post#84).

 

[ebiii]

Wow that’s a big difference! Very interesting!

Any other recent changes than rail pressure sensor? Different brand fuel, additives, oils or filters changed or anything like that?

No other changes, in summer I tried many auditives and it didn't work. I understand why now.

So the only change is this New fuel sensor.

I'll do few more regens to see if it improves over time.

Very interesting how a problem like the fuel sensor can be completely hidden while impacting the exhaust system so much

 

[n10n]

Very interesting how a problem like the fuel sensor can be completely hidden while impacting the exhaust system so much

Exactly. On the other hand quite natural as you mentioned earlier - air/fuel mix would have been off. But afaiu the O2 / lambda sensor is WRAF (Wide Ratio Air/Fuel) type which should be able to detect actual lean or rich burn... kind of strange there was no faults from that or rail pressure already earlier. So, maybe it wasn't really off by all that much?

Could you please reinstall the faulty sensor and record some further data for us to look at?

Just kidding of course. Let's hope your van stays faultless and improving on the DPF stats! Also the rail pressure sensor is probably one of the cheapest fixes you can have in these vehicles... that is, after it get's diagnosed.

 

[ebiii]

Exactly. On the other hand quite natural as you mentioned earlier - air/fuel mix would have been off. But afaiu the O2 / lambda sensor is WRAF (Wide Ratio Air/Fuel) type which should be able to detect actual lean or rich burn... kind of strange there was no faults from that or rail pressure already earlier. So, maybe it wasn't really off by all that much?

Could you please reinstall the faulty sensor and record some further data for us to look at?

Just kidding of course. Let's hope your van stays faultless and improving on the DPF stats! Also the rail pressure sensor is probably one of the cheapest fixes you can have in these vehicles... that is, after it get's diagnosed.

Hello ! After a few months I have gathered data again, I'll analyse it very soon !