04BC0 and 04BC2 - 8/2011 X5 xDrive35d w/115k miles
 

Yesterday afternoon after the vehicle had been sitting for over ten hours, a Engine Malfunction - Reduced Output warning was received. It was gone before I could really even see what it was. The vehicle ran fine on the way home, approximately 15 miles.

After sitting overnight, this morning again the warning was received. When I got to work, I used Carly to pull any DTCs. Only 04BC0 was present. I cleared it and went for a quick drive.

The vehicle ran fine and no warnings were received. I stopped and started the engine twice. After approximately 20 miles and after coming to a stop at a traffic light for approximately 30 seconds, multiple engine malfunction warnings were received. They would come on for about one second and then go away for five seconds. Once I started driving, everything was fine.

When I parked again, I used Carly to get the DTCs. This time:

004BC0 - Air Flow Meter - Signal too low
004BC2 - " - short circuit

Recent work less than 5k miles ago:

Transmission fluid and filter replacement
Active SCR tank replaced
SCR metering module replaced
Diesel fuel filter replaced
Engine oil and filter replaced
Engine air filter replaced

Any ideas on how I should proceed? Does not seem to be a common fault although there is a SIB regarding the HFM.

ETA: The vehicle sat for several hours since this morning. Took it out at lunch on nearly the same route and routine as this morning. No issues. The only thing I did in between was pull the engine cover off, look at the HFM and move the connector around. I read on another forum that a poorly connected HFM could cause issues.

After sitting for over five hours, it started and ran fine for about 15 miles yesterday afternoon with no issues.

It started and drove fine this morning on the way to work after sitting for over ten hours. Guess I'll chalk it up to a fluke.

Any chance water got into the connection?

It has been hot and humid here but under the hood is bone dry and dusty like the desert is dusty. It was your post, ard, that I read of checking the connection.

I was thinking back on this. Earlier in that week, it rained pretty hard. Those of you who know Norfolk, VA know that it doesn't take too much rain to turn some road sections into rivers or lakes. I drove through and on some petty "wet" streets and while it wasn't over the hood or even up to the hubs, I could see how some moisture might have made its way up into the intake. In any case, it hasn't been an issue since.