Glow Plug Fault Code

[PotsyDriver]

2007 X5 3.0d with about 125,000km.

All the glow plugs were replaced about 6 months ago as part of a larger piece of work (i'll save that for another thread - timing chain snapped).

Main and EGR thermostat replaced in last 2 months after DPF was not regenerating. After thermostats were replaced, it is now regenerating.

Now - new problem....

I've recently got the Carly app and when I first run the diagnostic test these are the results - It was showing 3 faults initially (just pasted in the relevant stuff below...)

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BASE: E70
BUILD-YEAR: 2007
MODEL: X5 (E70) alle/all alle/all (43)
FAULTS: 3
ECUs: 25
BATTERY: 14.9V

Engine / Motor:
- Fault: Glow plug cylinder 1
- Code: 004212
- Fault: Fuel filter heater control
- Code: 004B1C

Car Communication Computer CCC:
- Fault: Message failure
- Code: 00E18F

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I then cleared the errors, and reran the test (as per carly's instructions) and this error remained:

- Fault: Glow plug cylinder 1
- Code: 004212

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I've done a few searches for these fault code but have not come up with much. I'm still learning about what glow plugs are (!) so any advice or thoughts appreciated. The work that was done 6 months ago is still under warranty, so I'm just arming myself with all information I can should I need to go back for further work.

The car is otherwise seemingly running fine - doesn't appear to be running rough or anything, and there are no engine/warning lights on the dash.

If it makes any difference, the Carly test/s were done immediately after starting - and just idling. So the car wasn't warmed up.

Thankyou

Pete