Information Related to BMW X5 35d (e70) Glow Plug Fault:

Just thought I'd add this to the knowledge-base ....

My X5 35d was starting rough and throwing a glow-plug fault code.

Since I had an extended warranty I took it to a BMW specialist I've used for 20 years and completely trust.

The initial diagnosis was a bad glow-plug (which was correct); however, according to the technical literature it is common for the control box / relay attached to the glow-plug to also go bad - both were replaced.

To get to and replace these parts evidently requires removing the intake manifold.

Total cost was about $750, which was covered by the insurance, so I can be fairly certain all the work done was pre-authorized and necessary.
Seems like a lot for a single glow-plug, but a lot of labor.

Hope that helps, good luck.