smurf

You really need to get some live data out of this car with Techstream, or you are just throwing good money after bad.

You will probably have to remove the front passenger seat. The service plug is located under the rear right hand corner of the passenger seat. If you go to the 4 minute point of this video it shows the plug https://www.facebook.com/share/v/17XWgWV9dx/

A common failure point, but fairly easy and cheap to rectify. This post should help

This is his website. He is also on some of the Alphard Facebook groups and occasionally posts. https://www.aikotech.co.uk

WD40 is not the best choice for spraying on sensitive electrics. It leaves behind an oily residue that just ends attracting dirt. Electrical contact cleaner is the better choice as it washes away any contamination and totally evaporates afterwards. Get some, and use it to remove the WD40 from those connectors before you end up with more problems. However, even contact cleaner is unlikely to be the silver bullet you need. If the ECU has been having a regular bath but is now perfectly dry and intermittently working it is likely that it has suffered internal damage, possibly some corrosion. If you are feeling adventurous you could remove it and open it up. There might be visually obvious problems, there might not. It would be worth spraying it with contact cleaner whilst it is open, and you might get lucky and it was just some surface contamination or lingering damp causing an issue. Ultimately you either need to find someone willing and able to check for and repair the fault, or put a replacement ECU on and hope for the best. If you are prepared to travel, Kaspars Krumins in Wigan seems to get nothing but positive reviews for his work repairing Toyota hybrids, and he carries spares for Alphards.

If you are concerned that the rubber seal around the sunroof isn't sealing then don't be. The seal on the sunroof isn't designed to be water tight, hence the drain hoses. If there is a large visible gap then there could be an issue.

Erisin make aftermarket stereos. Some specific vehicle fit, and some generic fit.

It is an Erisin ES2712CN, made specifically to fit various Toyota vehicles.

I've considered cleaning and renewing the heatsink paste as it must be getting crusty by now. How much work was it to get to the modules off?

If you have a Campervanco conversion, your 12V battery is under the driver's seat. It doesn't crank the engine though, it just provides 12V power. Without that 12V though, it will not start.

Personally I wouldn't jump to use a liquid sealant before knowing what the issue is, as once that stuff is in there sealing holes it can seal any hole including ones there by design. If BMW really did put it in new engines I think they need to review their design and manufacturing processes if they couldn't get them to hold in coolant 🤣.

The most likely common failure point on the coolant system is a plastic T piece around the back of the engine. Unless you can actually see coolant leaking out of the block, I would investigate that first.

Leaks from the windscreen seal are not uncommon.

Mick said he has a Vellfire so I assumed he had just set up his profile incorrectly.

Thanks Mick, that is interesting info. Yours are for a Gen 2 and from a little bit of googling it appears the kerb weight of the gen 2s are little bit higher than gen 1 so the springs were possibly bigger from the factory. If so, uprated springs will be bigger again.