Back pressure reading odd with 2623

I have an 08 Sprinter here with around 200k miles. It’s posting fault code 2623 which will come right back when cleared. The main thing off that I noticed is the back pressure reading with key on is 700-715 hpa. The reading responds to revving but doesn’t match the intake air pressure and boost pressure which are both around 950 hpa.

I have tried a new back pressure sensor with no affect. Wiring checks out good to computer, getting 5v at supply. Is the computer keeping it at this reading until it goes through the drive cycles? Do I need to ignore this reading which is clearly not what it’s supposed to be and continue with fault tracing?

Other codes originally present were 2629 ash content too high
3121, 2079, 2078

Any help from the experts would be appreciated!

The EBP is important and MUST be the same as the rest in KOEO .
What about all the other sensors and the ambient temp sensor reading in KOEO?
Anything else flat lined?

Also check the gate valve operation at the cooler and the vacuum control operation.
What is the the differential pressure reading by the way when interrogating the exhaust system.
Any leaks at the EGR crossover tube and EGR cooler carcass?
P2623 offset drift fault at idle or at speed.
Do you have the sub code?
Dennis

It’s offset at idle 2623-001. All other temp sensors and pressure sensors seem to be correct. I did notice when running the vehicle the temp sensor downstream of egr cooler reading 55f which seems low given the exhaust temp sensors getting in the 300 range.

No leaks found in the exhaust or egr cooler area.

The key here is the backpressure sensor reading is off with the engine not running, so I can’t wrap my head around it being something mechanical like a clogged egr cooler or dpf. Unles, it’s waiting for the the drive cycles to complete before reading actual value from the backpressure sensor?

So are you saying changing over to another sensor gives the exact same erroneous reading???

That should be theoretically impossible or extremely unlikely, and if so might provide a very important clues as to what else it might be.

I agree the "engine off" reading of a sensor should not be impacted by any other mechanical fault.

First question of course (no offence) might be are you in fact changing the correct sensor which is giving the erroneous reading? I suspect it should read immediately after installation, but if it can be run for a short time and retested just to confirm.

If so, and the identical error persists, is it possible there is some resistance in one of the wiring connections along the way to the ECU? This would affect both sensors the same way. I would try to trace this and clean and reconnect all of the connections.

Beyond that, you are back to head scratching and forum posting for further suggestions....

The sensor in question is the one at the back of the egr cooler. I have verified by unplugging the sensor and the reading jumps to 5000. Yes, I plugged up a brand new sensor from mercedes and got the same reading. I did not actually install it, but I believe it grounds through the wire ground only.
I checked wiring back to the ecu (had connectors off of ecu) and found no problems. I believe there’s an internal error in the ecu unless anyone has any better ideas.

Have you a GDE tune on this one? To be able to tune these, they must understand the ECU's inside out.

If so, could ask Keith if his tune could affect such a reading, or better yet correct for it.

Have you got access to an ECU you could swap out, and at least get the engine off readings from that?

Im here doing more test on it and found the atmospheric pressure sensor is flat lined at 700 hpa. I imagine that may have something to do with the problem??? I believe it’s internal of the ecm?

The atmospheric pressure can be read with star tool under:
actual values>all actual values>internal parameters

Sprinter serviceman said:

Im here doing more test on it and found the atmospheric pressure sensor is flat lined at 700 hpa. I imagine that may have something to do with the problem??? I believe it’s internal of the ecm?

Click to expand...

Remember the atmospheric pressure sensor works in concert with the ambient temp sensor. to achieve air density readings & correct fueling! Have you checked that ?
For info the ambient temp sensor signal for some quirky German reason is routed through the SAM module (scabbed) on the side of the main fuse board .
Check area carefully for signs of a previous collision repair that has beaten up the wiring fuse board and SAM module & gone unnoticed .

With all that stated I have seen and replaced a fair amount of 2007 & 2008 PCM's due to the problems you are experiencing after having concluded the PCM board is the issue and/or the software is the problem
For me the cheapest option has been to ship it to SOS diagnostics and have them either re-flash it or supply you will an exchange unit. They have a rig set up to assimilate the problem you report to them.This has worked for me countless time instead of invoking dealer help with security string code downloads etc.
Hope that helps in some way.
Dennis

I previously sent the computer to SOS and it was fixed for a good 5 months, 4000 miles, now back to the same conditions. I plan to thoroughly checked the Sam and the outside temp sensor, and engine wiring. Any new insight on this? I see another recent post with a member dealing with the same problem.

Sprinter serviceman said:

I previously sent the computer to SOS and it was fixed for a good 5 months, 4000 miles, now back to the same conditions. I plan to thoroughly checked the Sam and the outside temp sensor, and engine wiring. Any new insight on this? I see another recent post with a member dealing with the same problem.

Click to expand...

I know this is an old thread, but I am having the exact same issues.

With cold engine KOEO I get a P2623 that won't clear due to Ambient pressure locked at 700hPa and Exhaust Backpressure 706hPa (MAP & Boost pressures ~1000)
Also
Temperature downstream of exhaust gas recirculation cooler is 296c & Temp Upstream of Catalytic Converter 290c while all other temps are ~20c

I am reluctant to spend the money to replace ECM as it sounds like your issue came back.

-Did SOS repair your ECM or replace it?
-Did you find a permeant fix?

Thank you for any insight

Had an 07 Dodge Sprinter having 2624-001 and 2623-001 codes that would not clear. Originally had intake port codes and soot content codes with the drift codes. They had the resistor in the swirl valve connector and had been driving it like that for an extended period. I removed the resistor but the drift codes would not clear. Did the MAF adapt and drift codes still present. Checked KOEO values just like I have seen lindenenginerring state multiple times. The exhaust back pressure sensor was not reading the same as the atmospheric and boost pressure sensors were. KOEO and the exhaust back pressure was still reading 7ish psi and did not respond to throttle manipulation. I have no idea what happened but after several key cycles and multiple start ups the back pressure sensor was matching the other sensors and then the drift codes cleared. Test drove for 60 miles and still all is well. I am sure there is an issue but at this time I can't account for what caused the sensor to start reading properly. Only thing I can figure is the MAF adapt process was not an immediate thing. After the drift codes cleared the module also started reading soot level where as before the soot and ash level readings were always a constant 0.