chimaera

A generic OBD scan tool will only be able to read OBD standard codes from the engine and transmission. For anything beyond this you will need a VAG specific tool. IIRC there's a thread in the diagnostics section of people with VAG specific tools who are willing to help out other owners: you might find someone near you there who is willing to help you out.

I summarised as much information on the rear suspension setup on these cars as I could find in the post linked below: 1x White 2x Orange is the part number you found (1K0 511 115 BH) for PR 0YD which is weight range 4 (very low). I would suggest in the first instance if your suspension is sagging that you replace the dampers. These have a sealed gas capsule in them that adds some spring stiffness and ride height. Eventually the capsule leaks and the dampers sag which makes the car sag. Your car is probably the standard chassis which is PR 1JA for damping meaning the p/n for your dampers is 1K0 513 029 JE. You'll need to replace the bolts securing the top of the damper to the body, and the wishbone pinch bolt at the bottom (I can't recall p/ns offhand for these but a dealer can get them easily for you). I found even with new springs and dampers on my car, it was still sagging a little, as it's only weight range 6 and carrying a towbar. I added a set of MAD helper springs as suggested by @3T51704x4 in one of their threads on suspension. They have restored the rear to its correct ride height.

Is the engine a TSI or HTP? Was it definitely the oil warning light and not some other symbol that might look like it? (If you have a picture of it that would be helpful.) There are two possible warnings related to the oil system: pressure and level. The pressure switch is always fitted, the level switch may or may not be. The pressure switch is inserted into the oil pump housing and will not be a microswitch like the one you have pictured. The oil level sensor from what I can see would not be a microswitch either. My hunch is that it might be the bonnet closed sensor or something like that.

One advantage of the torch over a phone is that it's magnetic so you can stick it to a metal surface and have both hands free. Handy if you have to fiddle with stuff under the bonnet.

If you need something to support the hub against the spring while you unbolt stuff, a bottle or trolley jack will do the job fine.

Make sure to replace the springs on both sides.

There's a temperature sensor in the Climatronic control panel which I think is the main cabin temperature sensor. Each dashboard vent has one too I think. Really you're going to need diagnostics to see if there are any faults reported, and also read out each sensor via measuring blocks. You should also run output tests on each actuator in the system. In both cases you're looking out for odd values/behaviour.

Owner's manual can be downloaded from https://manual.skoda-auto.com/004/en-com/Detail?model=Superb_3T&edition=05-2014&market=&manualLang=en Page 220 describes the procedure to replace the bulb, although weirdly it doesn't say what type of bulb it is. Service manual says it's a H7 bulb.

Pin 10 on the 13-pin trailer connector routes straight back to the SC fuse panel, to one of 43/44/45 (I can't recall which) so I'd start by looking at those three and make sure they run correctly. I would also double check the pin assignments on the 13-pin connector. Mine had two pins mixed up during manufacture and it drove me mad trying to find the problem. They push out of the housing to the rear if you do need to swap them.

I pulled this map of the two connectors on the OE controller from the wiring diagrams a while back: it gives pin assignments and wire colours for both connectors. Weirdly, the factory wiring diagrams never show the SC9 connection which the Skoda installation kit comes with, so I've no idea exactly what it does or where it connects on the controller. trailer_wiring_summary.pdf

I think the first thing to do is get it scanned properly with a VAG compatible scan tool to see if any other modules in the car are throwing communications fauIts. If modules are not talking to each other it's reasonably likely that there's a CANBUS problem or one of the modules is faulty. A full scan of the vehicle will shed some light on this.

All of us are here on our own time, offering what we can from personal or professional experience. A lot of us lead busy lives and have to ration our time accordingly: once our car works again we move on with our lives. That's just reality. Even just finding the post after a week or two is a pain as it'll have disappeared way down the pages in that time. Sure it would be good to come back and post again if we can, but no-one has a right to expect it on a forum like this. Diagnosing problems in a complex engineered system is challenging even if you have hands on access and know what you're doing. As others have noted, the actual source of the problem can be far removed from where the symptoms pop up. Diagnosing over the internet based on limited information provided by a non-expert (as most owners are, no shame in it) is more challenging still. Then you have to deal with all sorts of cognitive biases that humans are blessed with in trying to unravel what might be going on. If you get a solid lead on your problem after posting it here, you're doing pretty well. I get the OP's frustration, but coming in with a thread title like that and demanding more from people who are probably already doing their best to help you out isn't cool. You catch more flies with honey

The glare from the number plate light would be really harsh to other drivers at night. Even brake lights can be harsh when someone sits on the brake pedal in traffic. It's about being considerate to other road users.

I have mine set to 010D000101000000. Can't remember what settings that corresponds to though. The long coding helper in VCDS is pretty good at highlighting what the options are.

There are three bulbs fitted to that module. One C10W in the middle and two W5W either side. LEDs are readily available for these and as far as I know you don't need to worry about load resistors since the BCM doesn't monitor these for bulb failures.

Cloned cables won't work with the official Ross-Tech software. Your only chance of getting it to work is with the cracked software it came with. Enthusiast 3-VIN version of HEX-V2 from Ross-Tech is 199 USD: https://store.ross-tech.com/shop/vchv2_ent/

Is it a genuine Ross-Tech cable? If not, it's unlikely to work. If it is, you have to go into the Options menu the first time you use it to check and confirm the interface is connected to the software.

Radio code is not really a problem any more. I would hope that whoever fitted the new battery coded it to the car though. AGM batteries need to be coded in so that the battery manager in the start/stop system can keep it in good condition.

Going outside the manufacturer's spec is not trivial. Lowering one end of the vehicle and keeping the other at the standard setting will change the kingpin inclination. This will change castor behaviour, and camber change during steering, both of which will affect grip levels. It will also mess a bit with static camber at both ends which could lead to odd/premature tyre wear because the angle of the wheel's movement plane will change relative to the road. I don't know enough about the car's suspension geometry to be able to offer an opinion on what lowering the front might do, and given that other people's safety and money are on the line, I'm not going to speculate further on it. I don't know of anyone who has done it, but that's not to say someone hasn't tried it. If you have the cash to spare you could try doing it yourself and see whether you like it. You could also contact aftermarket suspension tuning companies and see if they have developed a solution.

Before trying any modifications you should get the suspension geometry checked, including ride height per the tables I posted further up. It's common for the Superb to sag at the back due to worn springs and dampers.

Something definitely sounds off here. I would suggest that any further work gets done at a garage that's known for doing good work on VAG cars. Do not attempt to start it again until you can turn the engine through at least two full rotations by hand to ensure timing hasn't slipped. TBH if it was me, I'd want the belt job redone by someone with the right tools and who is familiar with the job. Sounds like the seller may have half-arsed it to maximise their margin.

Some quick questions that'll help with finding a solution: How tall are you? What spec is your Fabia? Have you explored the adjustment options fully for the seat? I would think swapping in a seat from a different manufacturer is going to be difficult to do. If you really think you need to change the seat, I would start by looking at PQ25 cars from other VAG brands, SEAT Ibiza (2008-2017), VW Polo (2009-2014), Audi A1 (2010->), particularly higher spec models which may have more options for adjusting the seat. Being based on the same platform means they should bolt straight in with no modification needed there. Airbags should also be compatible. The only tricky part might be adjustment if you swap in power seats to replace manual ones as you will need to find power for the adjustment motors from somewhere.

What about the CAN Bus & brake line connections at the BCM?

I suspect there was a lot of hacking involved, and I get the impression that @mushroomnris not interested in a non-standard install. Care to post details/pictures of how you did it?

Given the length of the Superb and the fact that the loom has to run from the fuse panel to the boot along the driver's side & then across the boot, it's unlikely the harness from any of the smaller cars will fit.