Hi RUM4MO. Just had a look at the fog lamps. There seems to be a wee screw, craftily hiding up a hole, which lets you take off the plastic trim so exposing the lamp fixings which, once undone allows removal of the lamp to access the bulb holder. So still puzzled about this bit of wire. Read the manual cover to cover too and saw no reference to it! Ah well.
Regarding jump leads. I've gone from being supremely confident in their use, through being "careful" when alternators and basic electronic control units were introduced, to being a "basket case" just thinking about putting them anywhere near a modern car! I'm quite surprised that my 2016
Ibiza owner's manual gives specific instruction on jump starting? It details cars without stop/start should be connected as I've always done it. All ignitions off and cars not touching. Then positive (charged) to positive (discharged) and negative (charged) to engine block (discharged) This was historically to avoid any spark igniting battery gasses and seems to still hold true. If you have stop/start the Positive to positive remains the same but the black lead goes engine block on one to engine block on 'tother. I've been thinking about this and I'll bet it's because this way the battery condition monitoring ecu will be part of the circuit? I believe that if this monitor, which is seeing a partially discharged battery, suddenly sees a battery at full charge there is a risk of it going "phut"! I may have got the detail of this wrong but I know there is an issue around these units. I've spoken to a number of people I know (mechanics) and they all say not to jump one vehicle to another - damage to either vehicle can occur. They do seem to think that a jump from a slave battery or one of these little power packs involve much less risk and they jump from a slave only. Also, and this is something I've done for years, when you connect up the slave let it sit for a few minutes - maybe 5 or so - before trying to turn it over. This allows a surface charge to build up on the plates of the flat battery so it will behave much more like a charged battery. In fact there is a case to be made for allowing the "flat" battery to gain charge in this way and then disconnecting the slave before turning that key. Unless the "flat" battery is very deeply discharged you'll find it will usually kick it into life.
A final wee thought. Before connecting up to the "flat" battery try the headlights. Do they come on reasonably bright? Of course they will not be as bright as usual, but they shouldn't look like candles. If the battery is that discharged I would remove the battery and charge off the vehicle (or with the leads disconnected) When a battery is that "flat" if you succeed in starting the car there is a risk that when you disconnect the slave battery, because the alternator very suddenly sees a large voltage drop it will spike a maximum output which just might damage multiple ECUs on the vehicle and, if connected to another vehicle may damage it too. Of course if you disconnect the battery leads on many modern vehicles you'll loose some saved settings (radio etc) but also on the very newest vehicles the car has to be taught to "speak" to the battery when a new battery is fitted - I don't know, but removing a partially discharged battery and then putting it back in fully charged may require some sort of aligning process to be initiated (out of my depth now) Of course there are "oddities" like my daughter in law's Jazz which must not have the keys anywhere near the ignition when connecting or disconnecting it's battery. It scrambles the key codes and means an expensive visit to the main dealers computer to sort it out. We had to jump it twice last year after my granddaughter found out
how to switch on the interior light! I didn't take any chances, making sure the key was well out of the way when connecting my slave and leaving the slave connected for ten minutes after starting for the batterys to more or less equalize voltages before disconnecting.
Here's the page in the manual showing the connections for my
Ibiza