35d P2457 egr / low boost / dpf high pressure

[73tiiguy]

The short version:

Check the change over valve (part # 11747810831) that sits on top of the EGR cooler. If it's not working, the dme will start throwing P2457 related codes. If you have a schwaben/foxwell tool you can drill down into the various menus and activate that switch if it doesn't move the flap, it's bad. Or you can pull off the vacuum lines, remove it and bench test it. If it doesn't click, then it's bad. If it does function as designed start looking elsewhere

I have put about 200 miles since replacing and haven't had a single hiccup yet.

#8 on the diagram
RealOEM.com - Online BMW Parts Catalog


Long version:


I recently had changed my thermostat and glow plug controller because my motor was usually running in the 172-180 degree range on the highway. I had been getting an occasional P0675 glow plug circuit. That cleared up, temps are not 192 to 203 degrees after the thermostat change.

I'm also using a JB piggyback device btw and for about 20k and have had zero issues related to it.

All good for about three weeks, even noticed an mpg improvement. Until I get the dreaded "engine malfunction reduced power" message. I was on my way to pick up my kid from school, so I kept going and took it easy on the X. I parked and gathered up my hellyen started up the X and it seemed to be just fine. About half way into the trip home it felt like I was dragging a 10 ton boulder - got the "engine malfunction reduced power"... OK

So I start researching what could be causing this and most of the relative BMW diesel posts seemed to point to vacuum issues.


I crack open the hood, remove the cover and start looking from split or cracked hoses and sure enough yah the ones that are above the turbos are pretty crispy. I splice and replaced those, as well as one that goes down to the large turbo. I checked the operation of the actuator for the exhaust manifold flap and it seemed to be working/retracting as designed. It held vacuum for maybe 5 seconds after engine shut off though, but at times a bit longer.

I was thinking that there was probably more leaks somewhere, so I started with the easiest item - The change over valve that sits on top of the EGR cooler part # 11747810831.

I simply disconnected the vacuum at the T above it, and capped the end. That seemed to solve the main exhaust flap actuator issue as it would now hold vacuum for at least 20 seconds.

I removed the change over valve, and sure enough it didn't respond to having 12 volts applied to it. I replaced it with a new and I have put about 200 miles since replacing it. I haven't had a single hiccup yet.

Now I'm just waiting for the gold infused braided BMW vacuum lines to arrive, along with the vacuum bracket/reservoir. I also have some gold thermal reflective tape that I will use to make an additional insulating pocket for the bit of exposed hose.