"Interesting" EGR P2355-002 fault

[Alex Crow]

This was a long long story, but I will try to keep it short.

The car - 2005 E220 Cdi
The problem - frequent and consistent 'limp home', in conjunction with the code P2355-002

The fault would always occur at a cruising speed of around 70 mph
The above is the only fault code logged, and translates as "EGR malfunction, EGR air flow is too low" (which means airflow measured at the MAF sensor is too high).
A read out of the snap shot data shows EGR control at max (95%), and MAF sensor air flow still too high.
Previous work by several other garages has covered just about everything you can imagine, including: replacement turbo, replacement inlet manifold, replacement EGR valve, replacement airmass meter, checking intake and exhaust systems for leaks and/or blockages, having engine ECU tested by ECU repair specialists, checking EGR passages for blockage, having software update to 2007 version.
Note that this is by no means an exhaustive list.

This job took some considerable time to diagnose, but I will cut to the end.
EGR function was always OK at idle, and the control of the EGR valve was verified on roadtest - see attached thumbnail for an example of the PWM wave form. The actual EGR function was fault free.
The inlet manifold flap control was another story however, and it was found that the ECU was not regulating the flaps at all. This was the key to the fault condition, at the cruising speed the flaps should have been closed, but because they were open more air was being drawn in than expected, and becuase this was during EGR operation (yes, at 70mph) the fault code was being logged in relation to EGR function. On close inspection it was found that the ECU was not providing a correct PWM wave form, with either no amplitude, or when there was amplitue the signal was just 'noise'. See the second and third pictures.
Interestingly the ECU was not logging any manifold flap related fault codes, even with the actuator disconnected!
So a new ECU needed, but that was not what we did!..........................guess what the remedy was, over to you.

 

[Cole@MBS]

I would have thought that the bypass shunt would have fooled the ecu if fitted??????

 

[Alex Crow]

Well done Colin, you got it.

We were able to leave the functioning EGR system connected (helping NOx emissions and warmup), with the patent CDI3 EGR mod also connected.
Car has been OK for hundreds of miles now.

 

[amb67]

Great story, I love reading things like this.

 

[Alex Crow]

Here is the snap shot data to go with the fault code P2355-002.
Often this info is of no help, but in this case it was vital.
We can see the RPM to go with our 70mph cruising speed, airmass actual values way above set values, and EGR open at 95% (max opening) in attempt to lower airmass to within the range.

Also a picture of the CDI3 mod in place, a small box (34x57mm) with components soldered onto vero board.

Finally a screen shot of the EGR test before any work done and when stationary, note airmass within spec and EGR controlled well within parameters.

 

[pnevesfoto]

Hi Alex...
I'm experiencing the exact same problem on my w203 C220 CDI 150bhp 2005 estate...
recurring limp mode (almost daily) associated with P2355 and P0401 codes, since new fuel impositions implemented in Portugal... less additives and no more premium fuel available...
already checked for split pipes, tubes and hoses, EGR clean and functioning well, MAF reading and no problem aparent (relatively new part applied at a MB dealer at about 1 year and a half)...

I'm considering the CDI3 EGR mod so I can get my car back to the good health it had before...

your info on this forum and others I checked is precious and I already owe you alot...

I'll be posting news for the developments...

 

[Alex Crow]

Hi Alex...
I'm experiencing the exact same problem on my w203 C220 CDI 150bhp 2005 estate...
recurring limp mode (almost daily) associated with P2355 and P0401 codes, since new fuel impositions implemented in Portugal... less additives and no more premium fuel available...
already checked for split pipes, tubes and hoses, EGR clean and functioning well, MAF reading and no problem aparent (relatively new part applied at a MB dealer at about 1 year and a half)...

I'm considering the CDI3 EGR mod so I can get my car back to the good health it had before...

your info on this forum and others I checked is precious and I already owe you alot...

I'll be posting news for the developments...

Hi,

If the fault is usually being logged at a steady 70mph cruise, I suspect you do have the same issue.
Good luck!

 

[Joda]

Hello Alex. I have a question here because this is so similar to my case.
Codes I read are
2359 - boost pressure, low pressure.
2527 - left EGR positioner, signal line interrupted.
2355 - exhaust gas recirculation, air mass is too large.
Story goes like this.
On my holiday not long ago, I had a black smoke from exhaust, and limp home mode after just some forcing of acceleration. What I could do at that moment was to checked for air intake leaks , than I cleaned MAF and MAP sensors with brake cleaner I had by me, and nothing changed. When I switched of EGR motor car started running great again, up to 100km/h or 2000rpm in 5th gear, and still do, but if I cross that limit while cruising it goes to a limp home mode. Before that happens kick start and everything else is working fine, accept when the engine is colder than, say 70C, and I force it more than I should .
So it was good enough for me to get back home. I figured I will clean EGR valve when I get back, but imagine my surprise when I pooled it out and it was almost totally clean. I put it back after some inspection and cleaning but the same thing was happening again. So I put it on my friends diagnostics and I read this 3 errors. Now I was thinking that it might be a bad EGR motor but could not notice anything bad when I cleaned it, accept it had some soot in upper part by the motor and under the plastic cower, could it loose pressure there? Would you suggest me to install EGR bypass and which one?
Thank you for the answer, best regards!
P.S. Strangely enough I own almost same model as you was talking about

 

[Wighty]

Hello Alex. I have a question here because this is so similar to my case.
Codes I read are
2359 - boost pressure, low pressure.
2527 - left EGR positioner, signal line interrupted.
2355 - exhaust gas recirculation, air mass is too large.
Story goes like this.
On my holiday not long ago, I had a black smoke from exhaust, and limp home mode after just some forcing of acceleration. What I could do at that moment was to checked for air intake leaks , than I cleaned MAF and MAP sensors with brake cleaner I had by me, and nothing changed. When I switched of EGR motor car started running great again, up to 100km/h or 2000rpm in 5th gear, and still do, but if I cross that limit while cruising it goes to a limp home mode. Before that happens kick start and everything else is working fine, accept when the engine is colder than, say 70C, and I force it more than I should .
So it was good enough for me to get back home. I figured I will clean EGR valve when I get back, but imagine my surprise when I pooled it out and it was almost totally clean. I put it back after some inspection and cleaning but the same thing was happening again. So I put it on my friends diagnostics and I read this 3 errors. Now I was thinking that it might be a bad EGR motor but could not notice anything bad when I cleaned it, accept it had some soot in upper part by the motor and under the plastic cower, could it loose pressure there? Would you suggest me to install EGR bypass and which one?
Thank you for the answer, best regards!
P.S. Strangely enough I own almost same model as you was talking about

Alex isn't on the forum anymore buddy

 

[star]

Alex isn't on the forum anymore buddy

Why, have I missed something?

 

[Wighty]

Why, have I missed something?

Yes you have buddy , he was last seen July 2018 , but I'm sure it was 3 years before that he last posted .

 

[RobF48]

This was a long long story, but I will try to keep it short.

The car - 2005 E220 Cdi
The problem - frequent and consistent 'limp home', in conjunction with the code P2355-002

The fault would always occur at a cruising speed of around 70 mph
The above is the only fault code logged, and translates as "EGR malfunction, EGR air flow is too low" (which means airflow measured at the MAF sensor is too high).
A read out of the snap shot data shows EGR control at max (95%), and MAF sensor air flow still too high.
Previous work by several other garages has covered just about everything you can imagine, including: replacement turbo, replacement inlet manifold, replacement EGR valve, replacement airmass meter, checking intake and exhaust systems for leaks and/or blockages, having engine ECU tested by ECU repair specialists, checking EGR passages for blockage, having software update to 2007 version.
Note that this is by no means an exhaustive list.

This job took some considerable time to diagnose, but I will cut to the end.
EGR function was always OK at idle, and the control of the EGR valve was verified on roadtest - see attached thumbnail for an example of the PWM wave form. The actual EGR function was fault free.
The inlet manifold flap control was another story however, and it was found that the ECU was not regulating the flaps at all. This was the key to the fault condition, at the cruising speed the flaps should have been closed, but because they were open more air was being drawn in than expected, and becuase this was during EGR operation (yes, at 70mph) the fault code was being logged in relation to EGR function. On close inspection it was found that the ECU was not providing a correct PWM wave form, with either no amplitude, or when there was amplitue the signal was just 'noise'. See the second and third pictures.
Interestingly the ECU was not logging any manifold flap related fault codes, even with the actuator disconnected!
So a new ECU needed, but that was not what we did!..........................guess what the remedy was, over to you.

This was a long long story, but I will try to keep it short.

The car - 2005 E220 Cdi
The problem - frequent and consistent 'limp home', in conjunction with the code P2355-002

The fault would always occur at a cruising speed of around 70 mph
The above is the only fault code logged, and translates as "EGR malfunction, EGR air flow is too low" (which means airflow measured at the MAF sensor is too high).
A read out of the snap shot data shows EGR control at max (95%), and MAF sensor air flow still too high.
Previous work by several other garages has covered just about everything you can imagine, including: replacement turbo, replacement inlet manifold, replacement EGR valve, replacement airmass meter, checking intake and exhaust systems for leaks and/or blockages, having engine ECU tested by ECU repair specialists, checking EGR passages for blockage, having software update to 2007 version.
Note that this is by no means an exhaustive list.

This job took some considerable time to diagnose, but I will cut to the end.
EGR function was always OK at idle, and the control of the EGR valve was verified on roadtest - see attached thumbnail for an example of the PWM wave form. The actual EGR function was fault free.
The inlet manifold flap control was another story however, and it was found that the ECU was not regulating the flaps at all. This was the key to the fault condition, at the cruising speed the flaps should have been closed, but because they were open more air was being drawn in than expected, and becuase this was during EGR operation (yes, at 70mph) the fault code was being logged in relation to EGR function. On close inspection it was found that the ECU was not providing a correct PWM wave form, with either no amplitude, or when there was amplitue the signal was just 'noise'. See the second and third pictures.
Interestingly the ECU was not logging any manifold flap related fault codes, even with the actuator disconnected!
So a new ECU needed, but that was not what we did!..........................guess what the remedy was, over to you.

Hello Alex,
I have a w211 S320cdi with exactly the same symptoms. Limp home mode occurs only when you are cruising at a steady speed. It sounds like I might have a similar ecu problem as countless components have already been replaced to no avail. I was just slightly confused though as I’ve read people install an emulator (4k7) resistor to fool the ecu into thinking the inlet flaps were working when they were actually disconnected and open. So wouldn’t in doing that mean when the egr is open it would be getting too high a volume of air than it expected?

 

[Wighty]

Hello Alex,
I have a w211 S320cdi with exactly the same symptoms. Limp home mode occurs only when you are cruising at a steady speed. It sounds like I might have a similar ecu problem as countless components have already been replaced to no avail. I was just slightly confused though as I’ve read people install an emulator (4k7) resistor to fool the ecu into thinking the inlet flaps were working when they were actually disconnected and open. So wouldn’t in doing that mean when the egr is open it would be getting too high a volume of air than it expected?

The resistor fix fools the inlet port motor into thinking it’s still connected , it works if there is no swirl flap fault at the time it is fitted . The swirl flaps are left in the open position.
its a common fix on the Chrysler 300 forums , with the om642 engine .
Ive had one in place for a couple of years now
Nothing to do with the egr.