Breezy_Pete

Just one, judging from the wiring diagram. Designated G39, which is normally pre-cat.

I'm sure I'm always reading that Connect is so rubbish that most owners don't bother using it even if free?

Nice graph, will have to think about what it may tell us. RPM signal will be generated within the engine ECU from crank sensor signal, and communicated to the Instruments via CAN, rather than t'other way round, I believe. Not that that helps particularly. I'll have another look at wiring diagram tomorrow, if I have time. Tempting to think it's a physical thing to do with engine movement and its effect on a loom wire rubbing on something (he says speculating wildly...). Oil level trace is suspiciously flat, must be some very heavy averaging, especially if the glitch is affecting that too. It would make sense for that to be smoothed loads though, I suppose. I'll do an oil level log on my way to work tomorrow and see what that looks like on my Polo.

You could also log (with VCDS measuring blocks in module 44) the terminal 30 voltage at the PAS module during start-up, and compare with a car not showing such faults. I can offer a comparison log from my Polo, but it won't be very comparable as mine has no glowplugs and lower compression, being a petrol engine. Edit, it does however have an 8-year old battery that was mistreated quite badly early in life when installed in an off-the-road Mk2 Golf.

How does the company you've linked to have anything to do with car leases?

Yes, that's one way to confirm whether the thermoswitch is behaving as it should.

So, show us this "the software"? Is it universal?

Possibly, but without evidence from VCDS correlating with gauge reading I'd say that's more guesswork than anything else. I took a series of photos just now showing VCDS/gauge comparisons on my Polo (see profile) during the 60-76°C warm-up section, At 60 (61, just missed 60) it's still very obviously not showing 90 on the gauge:

You are probably right. Something is causing it to sometimes see a voltage it is unhappy about, It could even be a problem internal to the PAS module that is pulling that voltage down more than normal. Apart from re-checking the parasitic current, I've run out of ideas.

I agree with @UrbanPanzer, just let your garage source them. Don't get suckered into the "but ECP has this amazing sale on!!" stuff. It's a marketing illusion, designed to make you think you're getting a brief, spectacular deal. You're not, they always have such discounting. It's just a tactic.

All that is doing is delaying when the PAS module is woken up (by the ignition-on voltage from fuse 7) and starts to read the local terminal 30 voltage it sees. That extra time will give the battery/system voltage a chance to recover after glow-plug and starter motor activity. That does seem to confirm that once it sees a good voltage at the ends of its thick, permanent 12V supply wiring, it is happy. Maybe try replacing that pair of wires with some harvested from a scrapyard car?

I think the sensor will give continuous data whenever ignition is on, but the cluster doesn't display what it reads until it feels like it (>50C). The two numbers, temperature and level are sent down that single wire to the cluster (not engine ECU) as a data stream, if I remember right, Level can be seen in VCDS as well as temperature, via Instrument cluster (17) measuring blocks, which might give more/relevant info about the origin of the misreadings. There may well be some rolling averaging of the numbers to reduce noise in the data, which might explain dodgy numbers if/when the occasional dropout occurs. If you do scrutinise solder joints and see nothing obvious, reflow the relevant connection anyway, if you have an iron and some thinnish solder; it can be hard to spot cracks sometimes. Having said all that, the engine bay is a much more extreme environment for wiring, and electrics/'tronics generally, so I wouldn't be surprised if the glitch was something going on in there; but not sure what.

'Normal for new car' sounds like typical dealership BS, though I don't speak from experience (and doubt I ever will). Are you doing a lot of very short journeys, with breaks between each? If not, I think there may be a fault with the crankcase breather system, if not something worse. Monitor coolant level in the expansion tank (mark it when cold and compare regularly when also cold).

Some of the apparent economy loss will be because the car will be travelling further per wheel revolution than with the old tyres, especially if well worn, I think. Can't be bothered to do any sums just now, but can't imagine that would account for much.

On mk1 the instrument cluster is pretty easy to remove, and then the circuit board pretty easy to remove from the plastic housing. Once you have the board out, you can examine the solder connections of the green connector by lifting the edge of the bezel. (But..) You may be able to provoke misbehaviour by just waggling the loom connection to this green plug while everything's still connected and engine running, after loosening the cluster enough to get to the connector. You might even be able to reach up to it from below with everything still in place, not sure. The sensor earth connects via a splice within the loom where a few earths join up.

I don't think you re-checked the parasitic current being taken from the battery?

That's brilliant. How to make your aircon work better? Ask it to do less!

I think it's unlikely to be easy to find a hard-copy, based on having looked for what there is on erWin Skoda and finding a pdf of 700-odd pages (covering CUPA and similar engines). Guess you could print it out if you've really got it in for trees. You could download the pdf for <£10 though.

In your first post you say the fan starts when the coolant is at 94°C. How are you measuring that temperature, and where in the system are you measuring it? I'm not sure about the details on a Felicia with your engine, but often the engine coolant temperature (as displayed by the gauge) is measured close to the engine head. The radiator thermoswitch is often close to where the coolant exits the radiator. It is understandable and desirable if there is a temperature difference between these positions. If there were not, your radiator would be doing a poor job.

Is fake tyres a thing?

It's connected to the powertrain CAN bus; I think that would not be possible if it were not an Electronic Control Unit (ECU).

Check this again. Post a well focussed, well lit close-up photo and/or give it a poke with a finger to make sure it isn't cracked.

Looks like it. So check the fuse first, not for blown-ness but for connection dirtiness or looseness. Then 3-way connector at the sensor, then you've got the two engine bay connections at the 14-way connector, pins 11, 12. Lastly the green 32-way connector onto the dash PCB. On earlier cars (mk1 era) I would've probably gone there first, but surely they must have sorted out making reliable solder joints there by 2011?

Yep, as sep says. L0L = LHD, the other the other.

312mm discs on your car correspond to a PR code of 1LL or 1ZB. The list on the data sticker usually doesn't include the front brake system PR code, bizarrely. See wheels, brakes Octavia (OCT) [EUROPA 2010 year] (7zap.com)