Breezy_Pete

The OP is determined he's going to do it with back-up power on, so no point in trying to persuade him otherwise, I feel. No need to worry about sparks, they won't do any harm, if they occur. Attaching jump leads or charger leads to the battery clamps will be fine. But he should make a better job of attaching the terminal clamps than the last person to do them.

Whereabouts are you?

From a thread about front shocks, and a similar confusing part number sticker, note something similar going on between the two contradictory labels, the arrowed one being the real part number

As mac suggests, @Ukpaul204, this (identifying the correct fitment part via VIN) really is the starting point you need to go from, before worrying about anything else. The sticker in your photo shows a VW group part number, but not necessarily the right one for that shock absorber, it may be a subcomponent of it. Reason I say this is that the part number has 512 as its middle section. Look at Crasher's list of compatible shocks, and you'll see that all the real, actual OE part numbers have 513 as their middle characters. If you look at parts catalogues for Superb or Octy rear shocks, I believe you'll find that they are all 513's too, so the number you're trying to cross-reference is not helping you at all!

The yellow wire continues into the cabin, changing to yellow/green at some point, and ends up at pin 22 of the 36-way connector at the instrument cluster. The red wire should go to earth. When pad is thick enough, these are connected, so shorting is the right thing to do. Earth the wire going into the 36-way, to see if that works. If not, are you 100% sure the warning light is for pad thickness, not e.g. brake fluid level?

Wildly improbable. No idea what that article suggests, but if you are thinking of changing the battery with engine running, please forget that straight away.

Generally nothing much is lost when changing batteries. Might just have to re-enable one-touch window operation. Note that both of those battery clamps appear to have been misfitted. The battery posts are tapered, and both of those clamps haven't been pushed far enough down the tapers before being tightened. When fitting to the new battery, loosen off fully and push down all the way on the post tapers, which should open up the clamps, that way the tightening won't end up running out of adjustment as both look to have in your photo.

Oh, fair enough. Many garages aren't keen on fitting supplied parts. Coil and spark plug part numbers here (once you figure out your engine code): LLLParts Injectors and seals here, I think; first item 2, and item 3 LLLParts

Why not let them buy the parts?

Don't fit an EFB or AGM type, your charging system isn't suitable. I could look up Skoda part number and Ah/CCA spec if you supply VIN, but dimensions won't be 'lookupable' by that means I don't think. That info is probably all written on the top surface of the battery anyway, so take a ruler out and measure it while you're there. Length and width should be easy to get, depth probably by just sticking the ruler down beside the battery vertically.

I agree on your last point (and the edit about Ribe) and yes, the terms are often muddled. Perhaps I should have checked with the OP exactly what his 'spline' bit looked like, but the advice about ensuring full engagement is never wasted words.

It's XZN, not XYN, which is triple-square, dunno what it stands for. "I've never seen 4 triangles with 60 degree points", you say, so I guess that means they don't exist?

Either M10 or M8, depending on engine type, I think. Triple square has 90 degree points, spline are 60 degree (4 triangles rather than 3 squares. Will fit and probably work OK, biut be extra-careful that they go all the way into the screw heads (hammer on end of extensions til you feel it bottom out). Yes, access is awkward. Keep turning the driveshaft to get each screw into most accessible position as you go.

What's your VIN?

The valve/rocker cover is not something you can remove easily, as I told you above. In fact, it's a huge job on this engine. So it's not the best thing to do at all. Instead, you need to find out if there is lots of oil leaking or going elsewhere, and why you got that red warning light. I think your assumption that it was because 'almost all the oil was gone' might be wrong. Please check the oil pressure switch as also described above,

Message me with your VIN, or post it here. I can check what the 'real' part number of your rear shocks should be, sometimes those labels can be deceptive.

Check your oil level, make sure it hasn't risen unexpectedly. I'm wondering if there's a fuel problem resulting in oil dilution, with corresponding lowering of viscosity when cold?

I wonder if the red oil light reported was an oil pressure warning, in fact I think it must have been. Level sensor (if even fitted) only gives yellow warnings, I think? Now the oil pressure could be low if there really was a hell of a lot of oil loss, but probably more likely to be a false alarm caused by a failing pressure switch. Classic symptom is oil inside the electrical connector of the pressure switch. This is mounted on the front of the engine just near the items 1a, 1b, 1c in the diagram above, green plastic body, single wire connection. Disconnect this and see if oil weeps out from within. If unfamiliar with releasing such connectors, watch this: How to undo VW wiring connectors. - YouTube

The pin 3 signal goes to engine ECU and BCM, now that I look again, but the pin 1 signal has opposite sense, 12V when pedal not pressed, open circuit when braking. Pin 4 and 2 as you say @Orchid70, supply and earth for the brake switch module. @xman, the bulb monitoring is inside the BCM, I believe, on facelift mk2s.

Only foglight and maybe reversing light I think JR, and the fault is probably just to do with the battery having gone flat.

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As far as I can see, on this vehicle the 12V signal from the brake light switch goes into the BCM on pin 43 of the black 73-way connector, on a thin black/red wire. The output that actually drives the bulbs is on pin 16 of the white 73-way on a thicker black/red wire. So look for the presence of both while pressing the pedal with engine running. You may see the former but not the latter, which would narrow it down to a BCM issue, I think.

The sealing is done with RTV silicone, but unfortunately I think it's a pretty big job to get the cam carrier off in order to re-do this sealing. I believe it would entail removing the timing chain cover, the chain, then the cam carrier, then cleaning everything up, reapplying the sealant and putting everything back together. It might well be worth renewing chain and chain tensioner at the same time as this would add little to the (extensive, I'm afraid) labour time, and could future-proof the engine a little. Sealant is shown here as item 8. I wonder if it's worth trying to bodge some sealant in via the spark plug orifices? Maybe worth a try to save hundreds, but would require some ingenuity to even attempt in a meaningful way I think. I would think there must be another way oil is getting consumed, as said above.

See https://www.briskoda.net/forums/topic/511390-a-common-error-with-vag-part-numbers/

Yes. Match everything. Why do you need one?