ok, so interestingly, I just went for a longer drive to get the car up to operating temp. After 45 mins, I cleared the codes, and reran the test.

The glow plug error is now not showing, but another one is!...

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Engine / Motor:
- Fault: Particle filter system
- Code: 004667
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again - still no warning lights on the dash.
I'm searching on this code - but if anyone has any insight please let me know.

Carly tells me its only 38km since the last successful DPF regen.

I'm new to the Carly app - Are these 'hidden' fault codes appearing/disappearing all the time? I'm sure some are serious and I plan to take them seriously - but is there a chance some are just transient and not really a sign of a bigger problem?