Breezy_Pete

Which bit is causing your problem? It's usually the crimp at the battery end of the thick cable isn't it?

Can you not get one made? Is it just the main high-current cable you need, rather than the 'alternator loom' which that part number seems to be?

Yep to all of that.

Odd. That comes from engine bay fuse 10, which is fed directly from battery positive. You checked that fuse, didn't you, including voltages on it? Maybe double check.

Maybe consider buying one of these type of voltmeters, so you can keep an eye on voltages during drive cycles? Dual USB Car Charger - JEBSENS Car Voltage Meter Car Charger with Two USB Ports, 4.8A / 24W, LED Display Built-in Safety Protection Fast Charging Compatible with All Smartphones and Tablets: Amazon.co.uk: Car & Motorbike I'm not recommending that specific one, there are plenty to choose from. Don't leave it plugged in 24/7 though, or it will itself flatten the battery.

Not sure that either of those relate to the original one.

Ah, OK, so probably only talking to/reading from Engine ECU and maybe ABS system?

What device has been used to read that fault code?

One other thought... Everything I've written so far has been based on the premise that it's the engine ECU that's complaining about the low voltage. How has that P0562 fault code been read? Does it definitely originate from the engine ECU?

The fuse 13 feeds go to pins 3, 5 and 6 with red/green wires. The fuse 10 feed, red/black, goes to pin 92. The cabin fuse 2 feed, black/grey, goes to pin 87. Earths, brown, are on pins 1, 2 and 4. Oh, and L, blue wire, goes to pin 70, DFM, blue/white, to 65. Good luck.

It's almost never the ECU (unless there's obvious water ingress into connectors, or wiring damage, but then that's not really the ECU itself). Your description of it sounds right. ECM stands for engine control module I guess. PCM is another name, Powertrain control module. All the same. The L connection goes to another control unit too, and I'm not too sure which one it originates from, but from experience of my cars I'd expect to see ignition-on voltage minus about 0.6V when ignition is on but engine not running. Once engine is running and alternator working, I'd expect it to exactly mimic alternator output volts. From alternator it goes to pin 70 of the engine ECU, and pin 32 of the brown 52-way at the onboard supply control unit (BCM) in the cabin. If that wire wasn't making it to the engine ECU, it may explain what you're seeing (assuming that it originates from the BCM). DFM is a pulse width modulated signal from the alternator that may go up and down from 12 (nominal) to zero or 5V to zero in a square wave with pulse width (inversely) proportional to the alternator's electrical loading. You may be able to see this change as loads are added/removed with a digital meter, as you may see an average voltage, depending on how the meter deals with such a pulse train. Doubt it's relevant unless it sits at one extreme or other full time, but I think that would generate a different fault code.

Last thing I can think of is to examine/clean any/all earth connections that go to the engine ECU. Not sure of exact locations of far ends but thick brown wire(s) coming out of ECU.

Hmm. There's also an ignition switched feed from fuse 2 in the cabin fuseholder, so measure volts on that one too if it has the metal pads.

It will only be switched on when the engine is running, I think? Measure the voltage (relative to battery negative), when engine is running, at either side of fuse 10 and/or fuse 13, if they are the fuse types with metal pads at the top to allow such probing.

In the engine bay? That's the one then!

That same fuse 13 still applies, as does the relay in position 1 of the under-bonnet fuse/relay box. Fuse 10 in there, a 5 amp one, may also be worth checking.

I'll check the wiring diagrams again now that I know the right engine code. E-box is the fuse/relay box under the bonnet, not the one in the cabin.

BKD engine code? Have a look (for corrosion) at the terminals of fuse 13 in the engine bay fusebox. It gives the main power feed(s) to the engine ECU. If that looks OK and is gripped snugly by its fuseholder, consider trying another relay in position 1 of the e-box; that feeds fuse 13 amongst others. Might also be worth cleaning up the ends of the main earth cable between engine and chassis.

Cabin fuses 23 and 14 are the first relevant looking ones I've spotted but I'll have to leave it there for tonight.

Suction cup (sink plunger?) on the clear plastic front?

Looking at circuits, it doesn't look like there's a fuse that could take out the purge valve without affecting a whole bunch of other stuff. Do you know what it looks like/where it is? Item 18 here: intake system; vacuum system; activated carbon fil... - Fabia(FAB) [EUROPA 2011 year] (7zap.com) Look at ebay listings for 1c0906517a for pictures. When you find it, examine the hoses in/out for damage.

I'll be nearby a week on Friday/Sat if the problem persists that long. Checked any fuses?

What year is the car?

Has the cat maybe been 'emptied' or removed? exhaust pipe with catalyst - Fabia(FAB) [EUROPA 2007 year] (7zap.com)

Locate and visually inspect the pressure sensor, they've been known to melt! Photo in this post: Is this pressure sensor missing a pipe? - Skoda Octavia Mk II (2004 - 2013) - BRISKODA