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Discussion Starter #1
Hi guys
After the P0401 code has been gone for a while I suddenly got P040D today. Actual description
P040D EGR Temp Sensor A Circuit High
So then the question is: which of the sensors is causing this? As I can see there are several sensors, but do anyone of you know which sensor that triggers P040D code? I've tried resetting it, but it jumps right back, even if engine is cold.
There is no lack of power, no smoke from tailpipes.
 

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Discussion Starter #2
Just to follow up on this case for anyone who meet the same issue.
Bought the pierburg sensor, 7.08369.45.0, made my own "lambda" tool (grinding down one side of a 17mm pipe), got the old sensor out, it looked pretty clogged, and installed the new one.
Cleared DTC and problem solved :)
 

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Just to follow up on this case for anyone who meet the same issue.
Bought the pierburg sensor, 7.08369.45.0, made my own "lambda" tool (grinding down one side of a 17mm pipe), got the old sensor out, it looked pretty clogged, and installed the new one.
Cleared DTC and problem solved :)
Did it solved p0401 for you?
 

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Discussion Starter #4
Did it solved p0401 for you?
There are so many possible causes for this. I replaced egr, that sensor, new turbo and steamed it. Eventually no more errors, but I can't pinpoint the actual culprit.
If you're having the same issue, try a few egr valve cleaners to check.
I live in Norway, and egr valves get clogged here a lot because of the climate..
Search the forums and try out the different suggestions.
P0401 usually comes from clogged egr, egr cooler or faulting sensor. Also clean the tubes to and from egr (intake).
 

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This is why you buy a VCDS and it pinpoints the exact issue instead of giving you a generic code.
 

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LOLz. Have you ever seen a VCDS scan result? Can you show me yours which only says P0401?
 

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LOLz. Have you ever seen a VCDS scan result? Can you show me yours which only says P0401?
Hehe. The car is sold, and I have been using VCDS since my first VAG car, approx 15 years, so yes I have seen them ;)
The P0401 has popped up on all my VAG cars, from Skoda Fabia, Superb (x 3 ), VW Tiguan and on the TREG.

Here's a P0401 for you since you're so eager to see it ;)

1 Fault Found:
4807 - EGR System
P0401 00 [096] - Insufficient Flow
Intermittent - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Mileage: 155500 km
Date: 2019.07.20
Time: 11:00:20

Engine speed: 1734.50 /min
Normed load value: 59.2 %
Vehicle speed: 50 km/h
Coolant temperature: 75 °C
Intake air temperature: 27 °C
Ambient air pressure: 990 mbar
Voltage terminal 30: 13.540 V
Unlearning counter according OBD: 39
Mean injection quantity: 22.24 mg/stroke
Control Module temperature: 29.6 °C
EGR_governor_deviation: -187.1 mg/stroke
Inj Ctl q Curr: 22.39 mg/stroke
Mass_air_flow_sensor_drift: 1.2413
Air_Flow_Rate_from_Mass_Air_Flow_Sensor_kg_h: 184.8 kg/h
Actual charge pressure: 1413 hPa

Readiness: 0 0 0 0 0
 

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Wait.... what? Are those "more details"? Noooo.... it can't be!

Amazing how all that extra info was part of the code, but you were only saying "P0401".
Even more amazing that someone who's been using VCDS for 15 years had to "guess" which sensor was dead when you could've just taken readings or logged the output to see which of them wasn't reading.

Thanks for confirming that you have oversized red shoes making up the majority of your wardrobe.
 

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Wait.... what? Are those "more details"? Noooo.... it can't be!

Amazing how all that extra info was part of the code, but you were only saying "P0401".
Even more amazing that someone who's been using VCDS for 15 years had to "guess" which sensor was dead when you could've just taken readings or logged the output to see which of them wasn't reading.

Thanks for confirming that you have oversized red shoes making up the majority of your wardrobe.
Ouch. What's your problem? Did you at all see the other thread I had on P0401 (https://www.clubtouareg.com/threads/p0401-egr-error-driving-me-crazy.289637)?
This thread is a "spin off" with a simple P040D that was quickly solved, and meant for knowledge sharing. Beeing nice isn't that hard, is it?
 

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Wait.... what? Are those "more details"? Noooo.... it can't be!

Amazing how all that extra info was part of the code, but you were only saying "P0401".
Even more amazing that someone who's been using VCDS for 15 years had to "guess" which sensor was dead when you could've just taken readings or logged the output to see which of them wasn't reading.

Thanks for confirming that you have oversized red shoes making up the majority of your wardrobe.
Could you please elaborate ?
Probably most of us had red shoes....Be a kind forum colleague and pinpoint the incorect reading/sensor on @dlysnes error log.
thank you in advance!
 

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Discussion Starter #12
Could you please elaborate ?
Probably most of us had red shoes....Be a kind forum colleague and pinpoint the incorect reading/sensor on @dlysnes error log.
thank you in advance!
Hi
I'll do my best to find it from last year. My vcds was used a lot on many cars, many readings and I sold it with the car. If I find it in my laptop I'll post it here :)
Btw, this is P040D, and not p0401.
 

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Could you please elaborate ?
Probably most of us had red shoes....Be a kind forum colleague and pinpoint the incorrect reading/sensor on @dlysnes error log.
thank you in advance!
Why don't you start a separate thread between me and you or us 3 so that we can all argue about it if that's what's required. In this post, it was mentioned that there was no other info. I'm not going to read all other existing posts which may contain other information, etc. before I comment on this post.

Unfortunately useful information was omitted and this caused me to use the 🤡 reference, and feelings were hurt. (BTW, I was also wearing my red nose when I read post #1 as I didn't see the "sensor A" part - so I'm hurt too)
When a full code\scan is posted, you can easily see additional info, even if it's just the descriptor on the very same line of the P code being referenced.

Replacing the EGT probe that he referenced would have IN NO WAY fix your EGR FLOW issue.
If you have an insufficient EGR flow code, then you can do output tests and cycle the valve, etc. to troubleshoot further.
Back to his "unknown sensor".... all EGT errors I've seen in my limited experience also say "sensor 1, sensor 2, or Gxx" which are indicators of which sensor to look at. Once you have that clue, you can log readings to identify the correct one. (actually, you can do that regardless of description)

Regardless, if users believe they will get faster help from the rest of the people reading their posts by truncating and eliminating all the other info, by all means, go for it.

Was that kind enough or still too harsh?
 

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Why don't you start a separate thread between me and you or us 3 so that we can all argue about it if that's what's required. In this post, it was mentioned that there was no other info. I'm not going to read all other existing posts which may contain other information, etc. before I comment on this post.

Unfortunately useful information was omitted and this caused me to use the 🤡 reference, and feelings were hurt. (BTW, I was also wearing my red nose when I read post #1 as I didn't see the "sensor A" part - so I'm hurt too)
When a full code\scan is posted, you can easily see additional info, even if it's just the descriptor on the very same line of the P code being referenced.

Replacing the EGT probe that he referenced would have IN NO WAY fix your EGR FLOW issue.
If you have an insufficient EGR flow code, then you can do output tests and cycle the valve, etc. to troubleshoot further.
Back to his "unknown sensor".... all EGT errors I've seen in my limited experience also say "sensor 1, sensor 2, or Gxx" which are indicators of which sensor to look at. Once you have that clue, you can log readings to identify the correct one. (actually, you can do that regardless of description)

Regardless, if users believe they will get faster help from the rest of the people reading their posts by truncating and eliminating all the other info, by all means, go for it.

Was that kind enough or still too harsh?
To be hones, i was kinda expecting you to say : . . this and this value can lead you to check this and this etc...but you rather clarify some generic philosophy of vcds diagnostic :)
Thanks anyway
 

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Hehe, we're all kind and doing our best :)
TurboABA, my readouts for this particular issue didn't indicate which it was. You're right, I should have posted it. My bad indeed, and I apologize.

H()rnet, it fixed the P04D error, but it was not part of the P0401 issue. TurboABA is completely correct. I suggest you do a complete vcds scan, auto, and get all errors from the whole system. And then log. There's likely more than one involved. If you don't have a vcds I urge you to get one asap. It's not cheap, but worth every penny indeed. Saved my a** and wallet numerous times :)
 

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Hehe, we're all kind and doing our best :)
TurboABA, my readouts for this particular issue didn't indicate which it was. You're right, I should have posted it. My bad indeed, and I apologize.

H()rnet, it fixed the P04D error, but it was not part of the P0401 issue. TurboABA is completely correct. I suggest you do a complete vcds scan, auto, and get all errors from the whole system. And then log. There's likely more than one involved. If you don't have a vcds I urge you to get one asap. It's not cheap, but worth every penny indeed. Saved my a** and wallet numerous times :)
Thanks for your answer. Actually i do have vcds and in my attempts to solve the issue i have replaced egr vavle, examined the connection between egr and intake manifold,confirm the function of the bypass valve on the egr cooler, confirmed the dif pressure sensor on dpf and have 2 different shops to do fairly the same ( diagnostics). . . i ran the egr cooler soot test on vcds as well . . .on this one i think i had some good values for the mass airflow (i do not remember well) on both with and without bypass....so far only effect on P0401 i have achieved with replacement of egt sensor.
And excuse me for posting on this thread for my unrelated error code :)

bye for now
 

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Thanks for your answer. Actually i do have vcds and in my attempts to solve the issue i have replaced egr vavle, examined the connection between egr and intake manifold,confirm the function of the bypass valve on the egr cooler, confirmed the dif pressure sensor on dpf and have 2 different shops to do fairly the same ( diagnostics). . . i ran the egr cooler soot test on vcds as well . . .on this one i think i had some good values for the mass airflow (i do not remember well) on both with and without bypass....so far only effect on P0401 i have achieved with replacement of egt sensor.
And excuse me for posting on this thread for my unrelated error code :)

bye for now
What does your maf reading do when you command the EGR to open?

How many g/s with EGR closed, how many g/s with EGR open?
 
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