Do you know the error code for pre supply air supply low error? I can find a fuel pre supply low error code (error 1260) but not one for air.

If it is the 1260 code, it is still likely to be wiring to and/or a sensor. The 1260 error can be triggered by a faulty sensor (or in your case, possibly wiring).

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Wayne
2005 BMW X5 3.0d (b 02/05)
2001 BMW F650GS Dakar (b 06/01)