Diesel: Intermittant reduced power
 

So my dad's 2009 X5 diesel has 56,000 miles on it, and it has now twice thrown a code and began operation under reduced power. Both times the warning went away after a restart. Both times the code was thrown at highway speed during a heavy throttle application. The code was scanned at the dealer once already and it read something like "charge air pressure unexpectedly low" or something like that. Basically a boost leak situation. Has anyone else encountered an issue like this or have any suggestions for troubleshooting?

IMO- This is not a boost leak.

I suggest you research the recall that affected the intake air temperature sensor.

I am about 99% sure that he has already had this recall performed on his truck. I can verify later. Does the replacement sensor have a superseded part number?

I agree, I would definitely spend some more time researching this. It is difficult, to give any kind of diagnoses without some more information. If your X5 did set two codes, what were they? Were they the same code? And if you're saying your X5 set computer codes twice, then went into a reduced power mode.... the codes did not get reset after a restart. They would have been there until someone cleared them.

Find out some more about this and go from there.

My point is that there are some known issues with the intake temp sensor/control system... There has been multiple recalls... A recall is not infallible, there cam be other issues that interact with the components in the recall... do a search.

Let me start:

http://www.xoutpost.com/846433-post20.html

SES/CEL: Code 4BB2....Anyone else? - Bimmerfest - BMW Forums

SES light, NOX sensor - Bimmerfest - BMW Forums

First order of business is to find out THE CODE IN YOUR CAR.

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