Surprised to see this code hasn't cropped up on here before. One of the permanent faults on my GAP tool is this:

B1D24-64 - Glow plug circuit - Algorithm based failure - signal plausibility failure (2B)

A couple of threads on the Disco forum suggest it refers to the glow plug in the FBH.

I assume it means the glow plug is faulty. Might explain why my FBH never puts out anything more than luke-warm air, not that I ever use it very much.

Can the FHB glow plug be replaced or does the whole FBH need replacing? 2012 Vogue 4.4 TDV8 automatic (LHD), Santorini Black
2008 Vogue 3.6 TDV8 automatic (LHD), Java Black

It's that time of year when all of the winter comforts of the L322 decide to give up! Mine is also throwing this code at the moment. Have you got anywhere with it before I fire up the parts cannon?

No, I've only seen the fault since I bought the GAP tool two months ago. I don't want to buy a new FBH if the glow plug - if that is truly the problem - can be replaced independently. 2012 Vogue 4.4 TDV8 automatic (LHD), Santorini Black
2008 Vogue 3.6 TDV8 automatic (LHD), Java Black

I've seen kits online which include bolts, a gasket and a plug but not sure if it's the right part.

After googling a bit:
The FBH is a Webasto Thermo Top C

Some posts (not on ffrr) suggest it's not that hard to remove the Webasto and replace the glow plug.
(German engineering... )

Does yours make this light whirring noise when the FBH fan speeds up/down? 2012 4.4TDV8
2000 Honda S2000