There are two different DTCs for the glow plug. One leads me to believe that they indicate trouble with the control circuit, i.e., the module. The others seem to point to the glow plug specifically. I saw the two different types of glow plug codes, read some anecdotes on the internet and didn't want to get in there twice so I did the whole kit and caboodle and replaced everything. I had to do it again because the new OE glow plug failed at cylinder 1.

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8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim