Immobiliser Activated Golf Mk5

[itavaltalainen]

What were the fault codes on the scans?
The immobiliser check is in the dash, using the K-line it talks with the ECU which then allows engine start - or not.

How did you get it scanned? All units or just ECU?
Have you had the keys rematched at all? Might be a fault in the instrument cluster. ECU itself is more rare and you normally have fault codes relating to 'internal electrical fault'.

[SubSub1]

Hi all, noticed that someone has resurrected this thread just like I did back when we experienced these problems. I'll give you a quick run down of our problem and solution. We bought the car second hand and experienced the problems shortly afterwards. I'm afraid a cannot recall any fault codes but.
Our issues.....
When ticking over car always wobbled, rough tickover much like a misfire but it wasn't that.
Hot starting took quite a few turns.
We began suffering from immobiliser messages and engine would cut out within 2 seconds of firing. Car would eventually start and drive ok after many tries.
I carried out the following repairs for various reasons whilst curing this:-
Check Cambelt timing - all ok
Replaced camshaft position sensor - no change
Change crank position sensor - no change
Replaced vehicle battery - no change
Replace instrument cluster with used item - no change
Removed engine ecu stripped, checked for connection issues or dry joints on the board - no change
Replaced the entire key with genuine VW item - no change
Eventually I found some information relating to a software update that could perhaps remedy this. I took the car to our local diagnostic specialist who (after my insistence) pressed the support team of the machine he used to eventually be given an update for the car's engine ECU software.
As soon as this was carried out, we no longer suffered from the lumpy idle, hot start issues or non recognition of key.
THIS WAS THE FIX! After the hours of work and research, it turned out we simply needed a bloody software update. We kept the car for a month or so after but I had been so scarred by the whole experience, we sold it! Bit of a shame, it was a lovely drive! Moral of the story, always insist on a software update!!

2004 Golf MK5 2.0TDi GT DSG

Kind regards...Dan

[jeroom]

How did I get it scanned? A guy off another forum with a VAGCOM and software came and plugged it in and did a scan then tried a reset, but no joy. Not sure what you mean by all units or ECU? I don't know what a K-line is?
Not had the keys rematched because it didn't seem like the keys were the problem - either both keys work or both don't, and it's intermittent. I've been told it might be a fault in the instrument cluster before, and was poised to get a 2nd hand replacement and take it somewhere to be installed/remapped/keys recoded, but then it ceased for 6 months.
The thing with this is I've been very confidently assured that it's lots of different things now and it's a little hard to know who to believe. That's why I'm interested to hear how people who've had the same problem got it resolved. Money is an issue.

I only got a copy of the first scan but I'm confident the second was largely the same, cos I remember thinking it was a waste of time, but the "electrician" who came out insisted:

Engine:

17978 - Engine Start Blocked by Immobilizer
P1570 - 35-10 - - Intermittent

18263 - Powertrain Data Bus
P1855 - 35-10 - Software Version Monitoring - Intermittent


Brakes:

01435 - Brake Pressure Sensor 1 (G201)
008 - Implausible Signal - Intermittent


Airbags:

00532 - Supply Voltage B+
07-10 - Signal too Low - Intermittent

Instruments:

01176 - Key
07-00 - Signal too Low


Central Conv.:

00934 - Electric Window Motor; Rear Left (V26)
35-10 - - - Intermittent
00935 - Electric Window Motor; Rear Right (V27)
35-10 - - - Intermittent

[jeroom]

Thanks a lot for the update Dan - appreciate it. Well I couldn't afford a new ECU and it wouldn't be worth it for the age of the car but I've got someone lined up who could try a couple of things out there if it did turn out to be the ECU.
In the meantime just wondering if I might have missed a trick with things like relays, ignition switch, grounds etc. Checking under the wheel tomorrow to make sure no loose connections or corrosion.
Really appreciate the update though Dan - thank you.
David.

Edit: sorry it was a while between me reading that and replying, so your fix wasn't actually a new ECU, but a software re-flash. The guy I've got lined up suggested this as a first line of attack so I may well end up trying this as it's about the cheapest possibility to try first.

[itavaltalainen]

David, your fault is unlikely the same as Dan's. The mk4 and mk5 are very different beasts! I think the software "update" Dan received may have simply been an ECU map without immobiliser, which cured the symptom but probably not actual fault.

The reason why you read that so many things can cause your issues is simple - the system is quite complex and different faults can show the same symptoms.
With regards to the fault codes you posted I would look at a connection issue between the reader coil and the instrument cluster or the cluster itself. Iirc the reader coil does not go directly to cluster but via central electrics, so worth checking there (and to cluster) as well.

The powertrain databus error message could also point to issue on k-line (this is the diagnostics line that the different control units in the car - like immobiliser and ECU - use to talk to each other).

Alternative would be to disable the immobiliser in the ECU itself.... though personally I'd keep it and fix your issues. But I might be able to disable it if you're interested.

[jeroom]

I'm not going to disable the immobiliser as I understand that would invalidate my insurance.

Yes, I do realise that Dan's problem might well not be the same as mine, and that the issue can be caused by many things. Wasn't labouring under any delusions there to be honest. Just gathering info for my own knowledge and trying to build up a picture of the kinds of things that cause these problems and the kinds of things that can fix them. Pattern recognition etc.

An electrician confidently assured me that the pickup coil needed replacing, but then I found out you can't just get a pickup coil on its own, and that the cost of a new barrel was too much. So I asked for second opinions about this diagnosis on a forum and someone disagreed that it could be the pickup coil given the symptoms, and asked me to test the resistance across it where the wires go into the cluster. It tested out ok so I crossed that off the list.

But I'm hoping to give it the once over tomorrow and may even retest that resistance just for peace of mind.

Thank you very much for your input and info about this. Much appreciated.

David.

[itavaltalainen]

Pretty crap that VW did not make coil separate on mk4 like it was on mk3 - where it was soooo much easier to replace.
Try to test wiring harness all the way to cluster - just to make sure it's not getting lost anywhere there.

If that is all OK I'd personally go for new coil, even if it means replacing the barrel as well (maybe get second hand one, just test it before putting it in).
Worst case give me a shout, am in Brum quite often. Disabling immo can still be done but would also only use this as last resort (even though insurance is unlikely to find out).

[jeroom]

Oh I agree with that. Lets face it they don't make these things so the likes of you and me can performing quick cheap fixes ourselves! The swines.

Sadly I dont know how to do this test of the wiring harness all the way to the cluster. I've got a multimeter but I don't know what to test or where.

At this point it's hard to say what I'm going to try next. I had thought you couldn't replace the barrel without getting new keys etc, but I'm sure I read where someone said you can do it without that(by swapping the part the key goes into maybe?).

So I guess it will have to be:

- checking/cleaning contacts on the reader and the ingition switch.
- trying a new ignition switch(not much logical sense but a cheap possibility to eliminate)
- ditto with coolant temperature sensor(heck of a long shot I know)
- fitting a seond hand barrel, and swapping the necessaries
- getting a matching second hand cluster and taking it to these guys I had lined up before to try that remap/reflash. Wasn't too expensive.

I really appreciate the offer of the immobiliser de-activation and I know it's probably a practical solution if all else fails, but given my luck with cars to date, I don't think I'm gonna go there!
Thanks a lot.
David.

[itavaltalainen]

Discount coolant temp sender, at current temperatures even if it was massively off it would still start (not -20 degrees like in nordic winter).
Ignition switch is cheap but given the fault codes it's a long shot.

After looking at ETKA I had a look online, seems there are also some reader coils on ebay for mk4, so looks like there are aftermarket companies who make just the coil
READER COIL - VAG IGNITION LOCKS - KEYHOLE MULTIPLUG | eBay

If you need cluster coding should it come to that I can also help you (as I said I have VCDS as well as K+CAN CMDR) - can code keys to cluster etc.

[jeroom]

Thanks for all that I.
Couldn't see a mention of Mk 4 on that rather expensive coil. The installation procedure gave me a larf though.
I'll take on board what you've said about the coolant sensor and the ignition switch but I'm loathed to discount anything just yet.
Thanks for the offer again.