It looks aftermarket - if it was factory I'd have expected a Toyota part number on it. I wonder if it has a 'ghost' type immobiliser on it - with those there's typically something secret you need to do like a button to press or whatever, otherwise the car won't start. Do you have to do anything like that? This box would be the part that detects that button press. I've seen (on a Range Rover on YT) ones where there's a box in the cabin that talks to a receiver under the fusebox which surreptitiously disconnects the fuel relay - engine turns over but won't start without the secret handshake.

Generally the Toyota hybrids are very reliable - Priuses are good for 350k miles. The 10 series has an issue with the inverter cooling pump (inverter overheats which damages the IGBTs), but is that a problem with the 20 series? My Gen2 Prius has never had it changed and it's at 175k miles. The one issue with the hybrid batteries is they don't like heat. In the 20 series (and the Estima) the battery is cooped up in the centre console with only a small fan at the base of the rear. Especially in hot climates like southern Japan, Malaysia and Singapore the batteries can get hot, and the fan isn't that great at cooling them. Also, if that fan gets blocked or clogged then it can reduce its cooling ability and the battery can overheat. Another reason why you should always run the aircon in hot weather. Typically it's the cells in the middle that suffer as they are the least well cooled. I have 3 bad modules on the upper bank (each module is 12 NiMH cells in the upper bank and 8 cells on the lower) so I'm planning to replace them and refurbish the rest when I've sorted some other jobs. For now it's still drivable but with fuel economy about the same as the petrol 2.4. I only get the fault code showing if I let the battery become over discharged - just let the engine run for a minute before turning off and it'll leave some charge in it. If you can get to London there are quite a few garages who will refurbish batteries - the battery is very similar to the 2006-19 Estima, and the hybrids of those are popular as London minicabs. Search eBay for 'Estima hybrid battery' and you'll find them.

I haven't found out anything about the unit myself but the label would suggest it's part of the immobiliser set-up so I would say it's needed if you want to start the vehicle. Maybe someone will be able to identify it.

The series 20 hybrids have a bigger battery than the series 10 so likely give better mileage than previous. The issue with hybrids from Japan is that they could have been stood for many months and this isn't good for the HV battery. Also the HV battery can need servicing as any part can which is not cheap. I needed my HV battery refurbishing after I had had it for just over a year (about 65k miles) but has been spot on since (4 years) . I would also advise changing the Inverter cooling pump asap after purchase (or get the dealer to do it) as these do go and can cause expensive damage if not caught in time. If looking at a hybrid again I would insist on getting a battery certificate to see how good the battery is and get professional advice- I would advise this for any Hybrid or EV import or domestic. If you can get the HV battery sorted a hybrid should be good for a long time and they do have little brake and tyre wear (in my experience) and the ECVT gearbox is reported to be very reliable.

They are fine to repair.

Hi, does anyone know if having removed this box from behind the radio will have stopped the remote key fob from working? I would try plugging it back in but refitting the radio and fascia panel was a real challenge and not something I want to repeat any time soon.