16785 - EGR System: Insufficient Flow

DanG144 said:

Did you ever do the basic settings 003 test? That specifically tests the EGR, and will test it no matter what Jeff did in the operational portion of the tune. Even on off-road tunes this test still works.

If this test works, then I think you may need to get an updated tune from Jeff. If it does not work, then you have system problems to fix. Either a bad EGR valve, or plugged cooler, perhaps.

Click to expand...

I did not, but I'm going to track down a vagcom in the next couple of days. I did hear back from Jeff and he has requested some vaglogs so hopefully that will clarify the issue.

thanks

Does the rediness flag reset for the EGR system (you need a VCDS to read this)? If it does not reset, there is no way the EGR routine can run, you will have no EGR flow (the EGR valve will remain closed) and therefore the CEL will not illuminate for insufficient EGR flow, since the EGR routine is not running. In Virginia, where I live, automotive diesels newer than 1996 MY are subject to OBD II testing. For the 2004 model year, one readiness indicator is allowed to remain at "not ready" and the car will still pass, provided everything else is in order. Guess which readiness indicator never resets itself on my BEW?

--Nate

So, I hooked up with a TDI Club member who did a quick visual inspection, test drive, ran logs, and looked for codes. Here are the first few values in the logs (not sure how to post the file but can email to anyone interested).
Tuesday 10 January 2012 16:41:59:52639 VCDS Version: Release 10.6.4 (x64) Data version: 20110418
038 906 016 H RC s01b EDC G000SG 6327
Group A: '011 Group B: '003
time eng spd boost boost act charge time eng spd egr egr actual Egr duty
0.12 903 1142.4 1020 80.5 0.29 903 200 485 100.6%
0.47 903 1142.4 1020 80.5 0.64 903 200 470 100.6
0.81 903 1142.4 1020 80.5 0.98 903 200 470 100.6
1.15 903 1142.4 1020 80.5 1.32 903 200 480 100.6
1.49 903 1142.4 1020 80.5 1.67 903 200 470 100.6
Below are some random notes that I took in talking with him.
-duty cycle for EGR high at 100.6%. Thought maybe "stuck open".
-mass airflow sensor 1100
-80% duty cycle on MAP sensor
-boost up to 2500 millibar
-turbo fine
-smoke limitation fine
-could use injection cleaning since a couple were slightly different
-wondering if there may be blowby since their was oil in the turbo boost hose, the connection was a little loose and it was a bit dirty around that o-ring
-thought i should check intercooler for puddled oil
-he also checked for codes and only the original code 16785 (P0401-000) and several glow plugs came up. I'm hoping that the glow plugs will just not come back. The fuel pump was just replaced since a friend borrowed the car and put regular gasoline in it, causing the fuel pump to fail. Maybe that repair triggered the glow plug fault (or maybe that makes no sense).
His conclusion was that there is something going on with the EGR itself, so he was going to "Ohm it out" and do some other things I did not understand.
Anyway, that is all of the new info I have. Any thoughts would be GREATLY appreciated.

I am baffled as to why you are getting the "insufficient EGR flow" code. Looking at the above operating peramaters, it appears your ECU has been tuned to request maximum air. Is this the parameter that the "1100" above represents? If it is, then there is no way the EGR could be operational, because the EGR flowing into the intake will cause less than specified air (the 1100 mg/stroke) to flow through the MAF sensor, thus tyhe ECU will keep the EGR valve closed to meet the requested air amount as best as possible.

Now if the 1100 is the actual air flow, and if the requested (by the ECU, because of its programming) is less than that, the EGR valve opens (and the throttle flap closes some) and them if actual air is still greater than requested air, the CEL comes for the EGR flow code.

I just re-read the parameters posted above. It appears the "1100" is the measured air flow, per the MAF sensor. The EGR must be blocked off or the EGR valve is not opening when the ECU commands it to. You need to find out what the "requested" air flow is. You'll need the VCDS again. At idle, requested air is around the 250 mg/stroke on cars with an active EGR system. I think. This is where your problem lies.

--Nate

Get that hose connection fixed. If it's the upper hose you can fit a doggie collar on it instead of replacing the entire hose which could be expensive.