Code is 123900.

Put in a new (rebuilt) turbo yesterday. Everything went well until I put on the EGR elbow. All new bolts and gaskets, everything torqued to spec. Dropped a bolt 3 times, third time I couldn’t retrieve it and ended up using a spare. I can feel the bolt I dropped with the tip of my finger, it it’s not magnetic and I cannot get a long needle nose or anything to it. It isn’t interfering with anything, currently. Then I accidentally put the shorter bolts into the EGR elbow to intake, so they didn’t have enough thread engagement and actually stripped when I went to torque them down. I went back today and tapped the holes and picked up proper bolts at the dealer, which were actually longer than the ones I pulled. Yesterday, prior to properly torquing down the EGR elbow, I immediately noticed loss of power, and thought I hadn’t seated the charge pipe o-ring properly. Took back apart and realized it wasn’t seated. Cleared codes and took for a spin. Seemed fixed, but today it went back in limp mode. Started monitoring actual values via DAS, and noticed EGR positioner stays at 0% when it should be >15. Also load state filter is at 22g which is odd as prior to turbo replacement it was around 6. Figured that may be the turbo pre lube, and any cleaner I used on resonator & charge pipe. After clearing codes it regains power, but soon after goes into limp mode. Before going into limp mode, boost hits up to 1900 hpa, though it’s should be 2200-2400 IIRC. Once it goes into limp mode it stays around 1000. It’s in the proper range when idling however, if not a tad high, which happens to be around 1000. The EGR itself is only 20k mi old, and opens properly w actuations in DAS, but doesn’t seem to close. I had the turbo professionally rebuilt, and a new actuator was put on it, so it should be ok, but I guess one never knows. Would a malfunctioning EGR cause low boost? Could it be the pressure sensor? Any chance I fudged the swirl flap motor? Would a clogged DPF cause low boost pressure? The low boost code hasn’t returned after torquing the EGR elbow today, but I only took it for a 5 min test drive. It’s still showing low boost in the actual values so I have a feeling it will return. I can’t imagine that the intercooler spontaneously developed a leak during the turbo replacement. I never removed the rubber hose that connects to the resonator. Maybe the o-ring at the resonator?

Sort of at wits end w this vehicle, any help appreciated. Thinking of getting the ECU remapped to delete swirl
flaps, EGR, DPF, etc, but not even positive at this point if that would solve this issue.

 

Spoke w the turbo rebuilder, he said an EGR valve stuck open would cause low boost, like a wastegate. So I’m assuming 0% is open. Could this be due to clogged DPF, or is the EGR shot after 20k mi?

Drove to work this morning, about 25 min. Didn’t throw the 123900 code or go into limp mode. I also didn’t really get down on it either. Actual values still putting boost low, and EGR at 0%. Odd that only thing to change was the turbo, didn’t even unplug the EGR. Only reason I can think the DPF load state to jump from 6g to 24g is the residual cleaner in the charge air pipe/resonator and the pre lube additive in the turbo itself.

Guess next step is to pull the DPF for a manual cleaning, and/or pull the EGR valve for inspection or
both.

 

After being easy on it around town, I decided to drive it home hard to see if I could trigger limp mode. I got on the interstate one exit further away from home than normal, and went two exits past my exit. Plenty of WOT, uphill pulls, etc. By the time I got off the interstate, the load state filter was at 10g, down from 24g. While monitoring the actual values of the DPF, I noticed the EGR temp sensor was at 60* C, which seemed a bit low. Stopped at advance auto to pick up some brake parts cleaner to clean the EGR pipe on the front of the motor that the temp sensor is mounted to. Ran the actuation for said sensor, and was able to both open and close the EGR valve. So it wasn’t stuck, but being told by the ECU to remain at 0%. Which, by the way is closed, not opened as I had previously and erroneously assumed. When opened the temp rises, closed it lowered. I left it open until it heated up to 110* C. I shut the vehicle off, and upon return the load state was down to 5g. On the way home I thought that maybe after opening and closing the EGR, getting the temp sensor up to +110*C, and the load state back within range, that maybe all was good. So I checked the EGR positioner percentage and viola, it was functioning again. Boost pressures are up, power is back, no CEL. Fingers crossed.

So in the end torquing down the EGR elbow fixed the 123900 CEL and limp mode, and getting a good drive to initiate a regen got the EGR positioner functioning again.