35d Limp Mode, Several EGR Related Codes

[M62 X5]

Picked up a 167k mi 2012 E70 35d a few weeks ago and the problems started almost immediately (I expected this).
After a week of driving, I got a CEL and scanned it with my generic scanner to get the P20EE code for NoX sensors. Since I only had my generic scanner on me at the time I decided to clear the code and see if it came back. It returned about a week later but this time I opted to leave it be and drive it to work to see if I could scan it with a better scanner and get a better idea of what code it is. Unfortunately when I went to drive it to work it went into limp mode merging onto the highway. To get the car out of limp mode I had to clear the code and drive the rest of the way into work. I figured it would be another week before it came back but upon trying to leave work the CEL came on and it immediately went into limp mode this time. I pull codes with a Foxwell scanner and got the following codes:

40D4 DDE: Exhaust gas recirculation controller position control
44DA Exhaust gas recirculation-rate control, control deviation
4862 DDE: Air system, air to EGR mass flow, plausibility
48DD Charging pressure sensor, plausibility
4B81 DDE: Exhaust-gas recirculation-rate control, control deviation
4C8C Exhaust backpressure before turbocharger, plausibility

I did some searching and found other threads where some similar codes were fixed by a MAP sensor replacement. So I removed the MAP sensor to check it and it looked fine, just a little oily. I wiped it off and then replaced it. Drove it around the block and no limp mode. I did also watch the boost pressure during the drive and it looked normal.

Does anyone have any insight on these codes? I'm a little stumped why initially I had NoX sensor codes but then after the limp mode incidents I had EGR and air metering-related codes.

TIA

[robinasu]

You need ISTA+ to diagnose this with the targeted diagnostic functions, otherwise it's a roll of the dice shotgunning parts and effort. BMW-TIS is also very helpful.

The EGR codes don't cause limp mode. A bad MAP sensor will cause a limp mode. My MAP sensor was intermittent for a month or so. Buy the BMW OEM part that's made in Japan. The other brands will break quickly. ISTA+ has a check for the MAP sensor.

If the EGR codes persist, I would pull off the intake hose and check the HP-EGR valve and see if it's all gummed up with carbon and if the HP-EGR cooler connection is plugged. The return spring on the HP-EGR cooler flap is a common failure. The HP-EGR actuates with an electric motor and if the system complains about control deviations it could be jammed with carbon. Unclear which code yours is referring to as the codes are cryptic which is why ISTA+ is key.

The vacuum lines to the LP-EGR cooler, and in general, rot at about 150k. The LP-EGR cooler uses vacuum to actuate the valve. When getting EGR control codes the LP-EGR is usually the higher probability root cause. Either the vacuum lines are leaking or the vacuum proportioning valve under the intake (aka pressure converter) is broken, or both, which is common. You have to remove the intake to swap out the pressure converter and vacuum lines. You should do this if you ever take off the intake for any other reason.

You should also google how to check the coolant temp using the cluster menu. Coolant needs to be close to 88C at all times otherwise the thermostat is bad. A bad thermostat doesn't allow the DPF regenerations to occur as they should, leading to many other issues, such as glow plug system problems. The thermostat usually dies before 150k.

The SCR codes will probably come back.

Step 1 is to get a new BMW MAP sensor in there and see what persists or get ISTA+ after the MAP replacement and dive in to the root cause functions. My two cents.

[M62 X5]

Understood, I'm downloading ISTA+ now and I'll get a genuine BMW MAP sensor in there to see what happens. To be honest I am planning on deleting it soon but I would like to get any issues taken care of before I start modifying. I will check with a scan tool on the temperature but the previous owner stated he just replaced the water pump and thermostat (I know this means nothing) but I will verify it is getting to temp

[M62 X5]

While I don't have ISTA working yet I did go ahead and look over the EGR and vacuum systems for leaks and didn't see anything glaring. I'll be able to dig into it more this weekend. I drove it around quite a bit watching the live data and everything looked normal. DPF back pressure was normal and it even went into regen and completed with no issue. The 2 codes that remained are
4862 DDE: Air system, air to mass flow, plausibility
4C8C Exhaust backpressure before turbocharger, plausibility
No limp mode for now

[M62 X5]

Finally got ISTA up and running and here is what I got. 004C8C and 004862 seem to be the ones I was seeing before. Although the actual limp mode issue is very intermittent. I am installing a new MAP sensor today and I'm doing a DPF delete this weekend. I will get a tune next week to delete EGR, DPF, and SCR and then drive it and see what happens

[robinasu]

Did you happen activate the guided fault finding and what did it recommend checking, first? Just curious. Good luck with the work.

[M62 X5]

So unrelated to the issue I was having with limp mode my plan was to delete anyways. Last weekend I deleted the DPF and low-pressure EGR. I do not have a tune quite yet as I'm waiting on my dongle. I also replaced the MAP sensor with a genuine BMW sensor as I thought that could be the issue. I have not had any limp mode issues since then and the codes that were seemingly causing the limp mode have not returned. Before I replaced the MAP sensor I did do the guided fault finding in ISTA and it concluded the MAP sensor was good, however I think it could have been an intermittent bad signal from the sensor or something. The sensor that was in there did not look like an OEM sensor

[robinasu]

Yeah, my MAP diagnosis was the same as it was intermittent. Sounds like all your codes are gone so that is great.