Snap ,Sounds like you have had a bit of a hack job done to delete dpf , that's why lamdas are held at 99.9 % .
We had a sprinter van t'other month dog slow ....no codes , no reading from differential pressure sensor , I un plugged loads of sensors off the engine ....still no codes , I knew something was off , read the file with our cmd unit and sent it to my chipping man ... he said the whole fault code library has been erased !!
Complete hack job on it for dpf deletion .
If you look at air mass values you will see there the same as the egr flow data blocks , the ecm knows from its scripted algorithms that when egr duty is say 20% that the air mass should drop by a certain value , so if you have vac loss at
the egr control solenoid the egr will not open as much so air mass will not drop enough . The ecm will drive the egr solenoid to get the actual to the desired if the duty goes out of its working window egr flow codes for to high to low will be
logged .
Did you rule out all the vac loss areas .... all the splitting / cracking vac pipes replaced , if you still get the code after that I would suspect egr control solenoid
Ray
Thanks for the support , yes still playing with the scope , we have got the pico 4 channel and just got the in cylinder pressure transducer kit
For complete diagnostic nerdyness here's a Audi a2 1200 fsi engine with jumped teeth on cam chain sprocket .
Green trace crank sensor ( digital )
Red trace cam sensor ( Hall effect )
Blue trace cylinder pressure transducer
You are looking for correlation between the green traces missing tooth effent .... the gap in the green trace , the missing gap is the missing tooth on the flywheel that the crank sensor references from , you just have to know what a good engine trace is like to know the correlation .
Here's the fixed engine , new timing chain kit and correctly timed up
All this diagnostic capability with even taking a rocker cover off or timing cover , just done from ecm wiring plug and a spark plug hole .
Told you it's for nerds ......Anyone still here Zzzzzzzzzzz hehe !!