Trilby

And as suddenly as the fault arrived, it has cured itself. I've been away for a few days so unable to get to a dealer for diagnosis. I drove to work on Monday and the fault was still present. On Tuesday I got close to work and realised that the Stop-Start had begun to work again. I could also now switch to electric only mode again. It is like the fault had never occurred. This was the same again today. I did notice when I left home on Tuesday morning that the Infotainment screen had turned fully off and restarted itself as I set off. I suspect that a background software update had fixed the problem. It is possible that the there was a sensor fault that could recur, but my money is on a bodged previous update has now been fixed. Time will tell, but for now it is all back to normal. Thanks to all for the responses and suggestions.

Another few symptoms to report. Does anyone know if there is a factory reset option for the engine management electronics? 1) Stop Start seems disabled in Hybrid mode, regardless of engine temperature, etc. 2) If I let the battery drain so it switches automatically to ICE mode, it will charge the battery even when my foot isn't right off the throttle. There is only a tiny blue charging bar, but it is definitely there. 3) I'm sure the car used to prefer switching to electric mode when reversing - not any more. 4) When I actively switch from all electric to Hybrid, there is a message which flashes up that says something like "Engine needs to run for longer". Note that this isn't me trying to switch to all electric - it comes up when switching to ICE / Hybrid mode. I don't recall having seen this message before, but it only appears for a few seconds and clears itself, so I could have missed it?

Now you mention it, I've had similar unexpected engine starts in the past. This feels different though as I have actively switched to Hybrid, then been unable to switch back, even though the ICE is up to operating temperaures. Also the engine being used to charge the battery is novel for me. My usual experience is that the battery is slowly used during hybrid running, unless going down a long hill. This time the battery is getting charged when driving along on the flat.

Thanks for the suggestion @Novascape. Is cleaning of the GPF a known event with the Octavia IV? It sounds credible, but this behaviour has been building over the last few days - is filter cleaning likely to take more than a few miles?

For the last couple of days, I haven't been able to switch from Hybrid to Electric modes mid journey. I start my commute in all electric mode and usually switch to hybrid mid journey and back to electric for the last mile - just to be in non-polluting mode in the urban bits of the trip. Now, I get a message about the electric mode not being available for a list of reasons, none of which apply. When trying to switch to electric, there was 60% plus battery remaining, the engine temperature (water and oil) was up to normal running levels. The outside temperature was around 8C, so cold, but not very cold. I was in an urban area, so doing no more than 30mph. This evening I noticed that at one point, while in hybrid mode and driving along on a flat road that it was charging the battery with a full blue stripe on the gauge - i.e. it was using the engine to charge the battery. The average mpg for the journey at that point suggests that it had been charging the battery a lot as it had dropped right down into the 30s - it should have been way higher at that point having again started in electric and only done about half the trip in hybrid. I stopped the car turned it off and restarted and it instantly went into electric mode and finished the journey (another 8 miles) in electric. I hadn't engaged sport mode at any point. Is there a mode that would create this behaviour? Does it sound like a dodgy over-the-air software update? It feels like something has gone badly wrong, but there is no warning coming up other than the key battery - as usual. Any suggestions? I think a trip to the dealer is in the offing, but I despair at visiting them. They seem to know nothing about fixing the cars they sell, but speak to me like I'm the idiot - if it can't be fixed by a software update, they are out of their depth!