Technical Ducato P0401 P0402 P0236 P0238 and limp mode its 2017 Euro 6, EGR changed, What do I check next

[theGman]

As many here I have similar problems with my 2017 Twin EGR Ducato. I have the 177hp version. For me trouble started in 2021 roughly a year after buying the van, and got progressively worse. At that time the van had done around 175.000km. At first an error every morning and no more after clearing that. Later it got worse, limp mode every 50 - 100km or so, not funny. Before stumbling over this forum & thread I replaced the HP-EGR valve (no improvement), the turbo solenoid and the MAF sensor (again no improvement).

After reading about the DPF and LP-EGR circuit causing this trouble and analysing with MES early 2022 I had ECU prog v32 installed and had a new DPF installed (ouch), also had the LP-EGR cooler and the LP-EGR valve changed out by a clean used pair I bought used. This solved the problem, it was at around 180.000km.

But now, some 40.000km further, the P238, P401 and limp mode are occurring again... I have done a longer testrun with MES logging using dataset #5. After ca 5 min the P0238 and P0401 errors occured. After clearing these, in the following drive no more errors. See attached freeze frame snapshots and the log files before the error, and the longer / warm engine drive after that.
My analysis is the LP-EGR is (getting) obstructed again, an independent check is welcome...
- Temperature after LP-EGR cooler is max 100degC, average 60-65degC.
- LP-EGR valve is mainly travelling between 0 and 4.7 (but is also showing mid range values).
- The DPF dP ranges from 10-65mbar which is not bad - but doesn't say much about there being a 'crack' in the DPF or not.
- Finally I've seen that the injector correction values range up to and above 3mm3/i - outside the FIAT recommended maximum of 2mm3/i (should I consider to have them replaced?).

I have a service scheduled for November 6th, and informed the dealer I will most likely want to have my 'spare' cleaned LP-EGR cooler installed. Also I've indicated that the DPF is supposed to have 24 months guarantee (will see what the dealer says about that).

Since I also have a spare LP-EGR valve, I have the option to make and test the mod that @Fredastaire proposed earlier - to change the 'disc cam' that operates the valve in the clean air inlet such that it does not fully close / stays open.

One question I have for that is concerning the checks the ECU can (and will) do. I would expect the ECU to check that the airflow sensor reads (close to) zero when the LP-EGR valve is fully closed. That can be done by the ECU - if the air flow sensor is upstream the LP-EGR valve. My van is not at home for another week (daugther is in Spain with it). Can someone check / confirm if there is an air flow sensor upstream the valve? If so I am not sure I want to try the 'disc cam' mod as it is likely to cause other limp mode failure codes.

I am -very- interested though in the result of the HP- and LP-EGR removal ECU tune that @Poachersmoon has done. If that proves to work without errors, getting the tuning company to make a version that only disables the LP-EGR would be my choice.

@aschoots, hi, I'm having similar issues as you, my van is in the garage just now, apparently an expert from Fiat Italy will visit the garage to try and diagnose the problem tomorrow. I've been reviewing your .csv files and comparing the figures with mine. Can you tell me at what time the van went in to limp mode. Thanks.

 

[aschoots]

@aschoots, hi, I'm having similar issues as you, my van is in the garage just now, apparently an expert from Fiat Italy will visit the garage to try and diagnose the problem tomorrow. I've been reviewing your .csv files and comparing the figures with mine. Can you tell me at what time the van went in to limp mode. Thanks.

Hi @theGman, it happened just before 336 sec in "file1".

 

[Fredastaire]

@aschoots Notably the LP EGR is either closed or fully open, no regulating the input of exhaust to make a mix blend forward to the turbo.
.
My thoughts on an alternative cam were because I had an LP EGR in my hands, further I was wondering about a trial however on investigation it's impossible to reach without the horrendous major expensive dismantling job. So - a trial is a non starter. Originally I bought the LP EGR thinking could I mount it remote and just plug it in and see what happens, this was a non starter because the unit I bought second hand had been stored with water inside and was heavily corroded so it went back for a refund.
.

 

[theoneandonly]

@aschoots
the freeze frame data for the 401 is precisely whati would expect from the lpegr cooler issue

Ducato twin EGR Engine with P0401 Code (2016 to 2019)

This does not refer to earlier single EGR systems or to later AdBlu SCR engines. Note this is a guide and not definative. It is up to you to make decissions. It is the result of my investigations of data from many contributors and discussion with...

www.fiatforum.com

Things to note: from the table
1 Actual Air Intake % of Desired is typicaly 25% with one example at 33% and desired air intake is huge.
2 LPEGR is fully open
3 All engines are warming up (EGR exclusion valve off) but close to temperature not cold.
4 Throttle position very close 6 of 8 11.87% others within .2%

The cooler temperatures are low the LPEGR valve runs from max to min. the max also exceeds 5.
The Cooler is blocked.

One question I have for that is concerning the checks the ECU can (and will) do. I would expect the ECU to check that the airflow sensor reads (close to) zero when the LP-EGR valve is fully closed. That can be done by the ECU - if the air flow sensor is upstream the LP-EGR valve.

The MAF sensor is at the front of the air flow no air flow measurement after the lpegr. the purpose of the lpegr valve is to mix exhaust and fresh gas even if the fresh air butterfly is closed the flap should be open the strangulation being due to a blocked tea strainer (at end of cooler)

 

[Fredastaire]

@theoneandonly I wonder if there is a chemical logic in the tea strainer being after the cooler?. Could the tea strainer be removed and alternative strainer be installed in a container at the silencer exit? In a position where it could easily be removed and cleaned every year at service time. I assume the tea strainer is there to stop carbon grains going in to the turbo vanes, causing blade wear / impact damage.

 

[aschoots]

@theoneandonly I wonder if there is a chemical logic in the tea strainer being after the cooler?. Could the tea strainer be removed and alternative strainer be installed in a container at the silencer exit? In a position where it could easily be removed and cleaned every year at service time. I assume the tea strainer is there to stop carbon grains going in to the turbo vanes, causing blade wear / impact damage.

I wouldn't go for that. There is a risk of scaling that has formed insite the cooling tubes to come loose. The tea strainer needs to be where it is now.

Good thought though, it may be possible to bring the whole cooler down the engine backside so it can be accessed more easily (without taking off the subframe).

 

[aschoots]

@aschoots Notably the LP EGR is either closed or fully open, no regulating the input of exhaust to make a mix blend forward to the turbo.
.
My thoughts on an alternative cam were because I had an LP EGR in my hands, further I was wondering about a trial however on investigation it's impossible to reach without the horrendous major expensive dismantling job. So - a trial is a non starter. Originally I bought the LP EGR thinking could I mount it remote and just plug it in and see what happens, this was a non starter because the unit I bought second hand had been stored with water inside and was heavily corroded so it went back for a refund.
.

It is not "horrendously" expensive, my dealer charged around 750 euro. OK, it's "very" expensive. And yes, a bit too much for a trial and error experiment. That's why it would be nice to know if the ECU checks for "no air flow" if the fresh air flap is fully closed. If that is not the case, the experiment may be worth trying.

 

[Fredastaire]

@aschoots I suspect with a LP EGR at 4.7 and blocked cooler that it's the inability of the the turbo to give the MAP any manifold pressure that throws the final limp mode.
.
Another thought, could we have a micro bore input pipe before the LP EGR flexi to periodically squirt DPF cleaner inside when the EGR is open?
.

 

[jansla]

just one question @Fredastaire @aschoots trying to understand better:
According to the definition of the P0238 fault code, this can be triggered if the voltage that MAP sensor sends to ECU goes too high (i.e. close to 5V). And MAP’s voltage level corresponds to the pressure in the intake manifold – am I right?

If the lp-egr being clogged by soot is guilty of the whole problem discussed here - how is it possible that this leads to so high boost pressure in the intake manifold (where the MAP sensor is located) that P0238 is thrown?

 

[theoneandonly]

@theoneandonly I wonder if there is a chemical logic in the tea strainer being after the cooler?. Could the tea strainer be removed and alternative strainer be installed in a container at the silencer exit? In a position where it could easily be removed and cleaned every year at service time. I assume the tea strainer is there to stop carbon grains going in to the turbo vanes, causing blade wear / impact damage.

Somene kind member cut his blocked cooler to show the construction. It is basicaly a long condencer that does the majority of the work, condencing out unburnt hydrocarbons and the burnt stuff, cooling and slowing it down. A filter at front may get clogged very quickly and gaseuos stuff gets straight through. There still needs to be one at existing position.

I wouldn't go for that. There is a risk of scaling that has formed insite the cooling tubes to come loose. The tea strainer needs to be where it is now.

Good thought though, it may be possible to bring the whole cooler down the engine backside so it can be accessed more easily (without taking off the subframe).

Totaly agree i was thinking @Fredastaire filter would need to be more complex but relocating the existing cooler if feasible is a good idea.

@aschoots I suspect with a LP EGR at 4.7 and blocked cooler that it's the inability of the the turbo to give the MAP any manifold pressure that throws the final limp mode.
.
Another thought, could we have a micro bore input pipe before the LP EGR flexi to periodically squirt DPF cleaner inside when the EGR is open?
.

Injection point for DPF Cleaner In principle its a very good idea. Early on under engine is easiest but cleaner needs to get to top. Having previously looked at my spare cooler a tube could be welded in a suitable position but then a fair bit of forming to get to a suitable position for use and of course a suitable fitment for blocking off.
As minimum this would be a good experiment for @aschoots if youve got the time with the cooler off. As a scientist i would fit one top and bottom and eventualy test efficiency/ effecacy of both.

 

[theGman]

@aschoots I suspect with a LP EGR at 4.7 and blocked cooler that it's the inability of the the turbo to give the MAP any manifold pressure that throws the final limp mode.
.
Another thought, could we have a micro bore input pipe before the LP EGR flexi to periodically squirt DPF cleaner inside when the EGR is open?
.

@Fredastaire Where abouts is the LPEGR cooler and DPF located? It looks like I'll be going down the route of replacing my DPF. Just wanting to get an idea of what needs to be removed to replace the DPF. If the egr cooler needs removed to get access to DPF then I'll probably get that replaced at same time. Thanks.

 

[aschoots]

@Fredastaire Where abouts is the LPEGR cooler and DPF located? It looks like I'll be going down the route of replacing my DPF. Just wanting to get an idea of what needs to be removed to replace the DPF. If the egr cooler needs removed to get access to DPF then I'll probably get that replaced at same time. Thanks.

Hi @theGman, to replace the DPF and/or LPEGR cooler a (steering?) subframe at the bottom of the engine needs to be removed. It requires 6 to 8 hours of work in a garage...

 

[Fredastaire]

The LP EGR cooler is one of the first items bolted to the engine block. The DPF is one of the last items. The cooler is therefore underneath and hidden by the DPF.
.
So for either it's a garage H ramp job to enable jacking the body up before dismantling the suspension and dropping the subframe. For any discussion with a local garage about doing the job it's worthwhile telling them that you leave the steering rack connected by it's hydraulic hoses dangling in fresh air.
.
I had my cooler changed more than a year back yet my DPF is still the original.
.
I keep a regular survey using MES recordings sent to @theoneandonly as I'm wondering how long before it re-blocks.
.
I'm told by a Fiat technician that there are exchange DPF units available from Fiat and that there are two different types, you have to make sure the correct one is ordered. Whilst I had a brief exchange of messages he no longer replies. I had similar contact with another Fiat technician in an East European country, he also stopped conversation. It makes you wonder if there might be a gagging order.

 

[theGman]

Well my saga just took a different turn. I got a call from my garage after my motorhome was inspected by a Fiat expert from Italy. The expert suspected / diagnosed a problem with my turbo. So, he managed to look inside the turbo with a borescope and found the remains of a sheared bolt that has smashed and broken the impeller blades. It was also mentioned that a bolt was found missing / sheared on my air filter mounting. The expert said that the only way for the bolt to have got inside was during the rebuild of my engine. Now waiting on his report and pictures before addressing it with the garage that installed the engine.

 

[Fredastaire]

@theGman whilst it's good that you have clarity for the problem, I wonder who pays? Then there is a question of where and how far has debris gone? Next in line down the air duct is the intercooler radiator which should act as a sieve for even small parts.
I would query how you change the turbo; if it's a subframe off / DPF off job then perhaps it would be expedient to remove and caustic clean the LP EGR cooler, a quick and easy job with everything else out of the way.

 

[theGman]

@theGman whilst it's good that you have clarity for the problem, I wonder who pays? Then there is a question of where and how far has debris gone? Next in line down the air duct is the intercooler radiator which should act as a sieve for even small parts.
I would query how you change the turbo; if it's a subframe off / DPF off job then perhaps it would be expedient to remove and caustic clean the LP EGR cooler, a quick and easy job with everything else out of the way.

@Fredastaire , My thoughts were to replace the DPF if already removed. As for who pays, that will be the sticking point. I spoke to garage that fitted the engine & turbo but their manager said he can't see how it is possible. So, maybe a complicated process proving blame and liability.

 

[Fredastaire]

@theGman I understand that Fiat now does exchange DPF units however there are two models and you need the correct one. Should you look at this route, if I'm right, then could you advise part numbers and prices.

 

[theGman]

@theGman I understand that Fiat now does exchange DPF units however there are two models and you need the correct one. Should you look at this route, if I'm right, then could you advise part numbers and prices.

At the moment i'm waiting on the garage coming up with a quote to replace turbo, this is not the garage that replaced the engine. Once i have the quote I'll post details and the way ahead.

 

[Fredastaire]

In past years I have used Midland Turbo of Nottingham to rebuild a turbo for a vauxhall. They are (I think) main Garrett service agents so if necessary they could rebuild your turbo, for me it was something like a two day turn around. I would personally recommend them.

 

[jansla]

There is a slight chance that my story is getting some solution (hopefully) or is not?, well the time will tell. It has begun 4 moths ago, details in this thread post#542. Several visits to different workshops in Austria, Germany and Italy during my summer travel and each time same reply: no cause for fault codes could be identified. Erase codes, drive along.
Last week the van was being tested and examined for the second time by my local Fiat workshop. They spent a lot of hours testing. Nothing cheap for my part. For the first time something was found! But I could not believe. They said that the MAP sensor was not the right one! I bought the motorhome as brand new. Mechanic has discovered that the MAP sensor mounted from the factory was Bosch 0281 006 028. According to the Fiat’s specification it should be 0281 006 076! How could this happen that the factory has mounted wrong one?? And another question (not answered by now) how could this wrong sensor been doing well for 5 years? As I could read in Bosch catalogue found here https://www.boschaftermarket.com/xr...y_specific/it/xx_pdfs_28/catalogs/sensori.pdf the right sensor for my van is 0281 006 076 indeed, while the other one is used in Porsche 911, and some other Fiats as well. But anyway the sensor fitted in factory has not made my van performing like 911 by any means. The pressure range for the right one for Ducato is 0.2-3bar while that factory fitted in my van is 2-3bar. As boost pressure in Ducato is quite often around 1.5-2bar so the wrong sensor was not that much out of range so maybe this is possible explanation that it has worked quite fine for 5 years and no longer now when some soot has accumulated (as the fuel/air ratio could have been not optimal) and fault codes came into live…


Any way a new 0281 006 076 is now sitting in my intake manifold and I hope that it’ll do fine. My advice for all of you getting P0238 and P0236: just check if you have the right MAP-sensor- don’t rely on factory!


At least something being wrong was detected for the first time. By now I have driven only no more than 100km but no faults and no limp mode (fingers crossed).