Breezy_Pete

"Clean Diesel" ring any bells?

So the best answer you could have given to my request for supporting evidence is: "No, I cannot, I was just parroting stuff I'd read". That would've been fine.

(Good) Science needs to be done by independent parties with no financial interest in the experiments. Varta are not that.

Sorry, I wasn't clear. I meant documented, repeatable, measurable differences; Scientific evidence, rather than assertions from other parties. This statement near the end is interesting, shame they don't name names. Many car brands do not even require an active recoding as the system recognize the new battery by itself.

Please supply evidence to support this assertion.

I'd be fascinated to hear/see measured evidence that the charging system does actually behave differently when coded for EFB vs AGM, on a given battery (whichever of those types). Has anyone ever seen any such experiment in this or any other VAG-group forum? It's about the only time I wish I had a more recent car so I could do the experiments myself. Logging Terminal 30 voltage during a few similar journeys with each of the two different codings would probably suffice.

I'd suggest double-checking the servo hose yourself, unless they report it as faulty, it's easily done, and if bad, quite easy to see or feel with a fingertip. This very recent post on the mk1 Fabia forum shows a typical late-stage failure: https://www.briskoda.net/forums/topic/498361-cylinder-3-misfire-12-htp-2007-64ps/?do=findComment&comment=5591291

What year is the car? How many miles has it done. Where are you located? Have you or anyone else ever inspected the brake servo vacuum hose? Since the VW specialist appears to have cost you a chunk of cash on a misdiagnosis, maybe they'd scan the car for free to tell you what fault codes it currently has stored?

I described how to test the wiring in my first post on 3rd October, I had the impression you'd proved this to be OK, from what you said here: But you didn't actually do the check I suggested, which I'll repeat here: "Unplug the connector from the pressure switch after you've started the engine. Get an assistant to short the loom wire connection continuously to chassis/engine/battery negative with a separate wire while you raise the revs above 1500. If the fault indication is still generated, there is a break in the wiring somewhere. If there is now no warning above 1500, the wiring is OK." It could instead be related to temperature increase and/or oil dilution during active regenerations of the DPF, so it might be an idea to try to spot whether there's a correlation between one of those happening and pressure warnings appearing.

@Robstelly I doubt your car has a freewheel pulley on its alternator. Take and post a photo end-on if you're not sure what to look for.

I'm not sure, but mending broken connections is rarely a bad thing. It would be really helpful to be able to see if the system voltage is doing anything mad at the times you're seeing the faults, so see if you can resurrect the lighter socket after wiring repair(s).

They pass through the same (2-way) connector pair on their way to the alternator, though separate wires all the way. Breakages are usually easily seen near that connector pair. Check fuses for the ciggy lighter. Does the battery light come on with ignition, before starting engine? That's a giveaway for a broken (blue) exciter wire if it doesn't.

Might be time for a compression test to rule out valve problems. The official info on those codes is as follows:

My feeling too. Take this quote for example, from @muddyjim's link "Self-learning system. If a battery is advanced in age, the vehicle system records the „defective battery“. If a new battery is installed without entering a BEM code, the vehicle will not recognise" So they'd have you believe that the vehicle system is capable of detecting when a battery is defective, but then can't tell the difference when a non-defective, brand new one is fitted and used? Pull the other one, frankly.

Sounds like the sort of rumour I'd want to put out there if I were working for VW-group or any other garage that has coding facilities. Bet there's no basis to it.

Strange one. Maybe grab one of those little LED voltmeters that plug into your lighter socket so you can see what the charging system is doing at various rpms. On your car I think the connector pair with DFM and alternator excitation wire will be the top, black pair, seen here just below the starter motor.

Nothing to code then. (disclaimer: to the best of my knowledge)

XZN by the sound of it, but be aware that these are sized in a confusing way. The 'M' number of the bit doesn't (always/necessarily/ever??) equate to the thread size 'M' number. Borrowing an image from here: TONE 3TS Triple Square (12P) Socket | Kouei Japan Trading Co., Ltd. (koueitrading.com) If you measure corner to corner on the head you can work out what size bit you need:

Does it have start/stop, or anything on the battery negative post other than a simple clamp? I imagine no to both?

Temperature or moisture/condensation could be a factor if you do have a poor connection. Have you looked under the bonnet to see if you can eyeball the wire in question, or get a hand/phone camera to it? Just inboard of the battery, and down a bit, near the gearshift mechanism. Grab a multimeter from anyone you know who has one and measure battery voltage first thing, before putting the keys in the ignition.

I had a Mk2 Golf or two. More or less same, I think.

Mk1 Fabia, the ideal car to teach you how to mend anything on a car.

Ignition switched 12V, yes. 3,4,5 all direct to ECU. Another recent post had glowplug errors as well as MAF fault that mysteriously vanished when MAF was sorted, don't understand how, but you never know. 😀

Looks like the same whether it's BJB, BXE or BLS. (Cabin) Fuse 29 feeds pin 2 of MAF through a black/green wire; that fuse also feeds a crankcase ventilation heater on some cars, which sometimes fail short circuit. So if it's blown and re-pops, find and unplug that heater. 3 to ECU pin 60 green 4 to ECU pin40 black/violet 5 to ECU 82 black

Nowhere near in my experience.