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Noob needs OBD2 advise (ecu communication)

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Gilo-T5 View Drop Down
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    Posted: 21 May 14 at 20:27
Good evening, I'd like like to get some opinions before the van goes under the knife and my wallet goes into the red

Basically my ecu can't be read by ANY obd2 device including VW's system.. This was first pointed out when the van went in for a remap in January.

I now have an ABS fault and once again cannot read the codes.. It just won't communicate ( LINK ERROR )

However using a Bluetooth module via obd2 port and dash command I can get temperature readings and revs etc

So.. Is my ecu bricked? Or is there another module that could be at fault (someone has mentioned changing the instrument panel)

The more info I can get and trouble shooting I can resolve myself the less workshop time it needs (hopefully)

It's an 2008 2.5 BPC kombi and running oem stereo so no K-line issue with diagnostic port

Any help/suggestions would be greatly appreciated before workshop time commences

Edited by Gilo-T5 - 21 May 14 at 21:44
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alonline Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 14 at 11:28
Sorry to sound stupid, have you tried vag com from Ross Tech??? ( with their lead)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gilo-T5 Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 14 at 12:20
Yeah I have a mate who works for VW I popped in while passing... And get the same message "link error"
Same has happened on another mechanic freinds snap on system and Delphi system as well as my eBay code reader
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alonline Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 14 at 12:46
PM master tech

Don't you love modern German technology!

Give me a Perkin's or Cat Diesel any day or a Honda.


Edited by Alonline - 22 May 14 at 12:48
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Post Options Post Options   Thanks (1) Thanks(1)   Quote gregozedobe Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 14 at 13:13
Is a bad electrical connection a possibility ?  Corrosion, bent/loose pin in port (or elsewhere), or my personal favourite hate - a broken wire with external insulation appearing intact.  Worth investigating at least.

Just wondering because you did get some communication with bluetooth thingy.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VW master-tech Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 14 at 18:44
Not too sure what to advise here as difficult without seeing what it comes up with, your mate did he use the genuine vw equipment? Does he work on cars or vans ? The new vw software odis will only communicate like for like so cant use a car machine on van if he is at a commercial dealer vaspc if updated will only work on crafter now. Best bet is to book a diag check at a dealer usually half hour charge and see what they say, shame your aren't closer to me as I have both vas pc and odis on my laptop for all makes vw, vwcv, seat, skoda, let us know what the dealer comes up with and may be able to givw better advise
VW WORX VCDS retrofitting and coding carried out, cruise control, mfsw, dis, locking adaptions pm for a quote
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gilo-T5 Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 14 at 20:36
Hi master-tech,

My mate works of Sinclair VW in Cardiff on the commercial vehicle side, I'm assuming the workshop equipment is up to date, he only plugged it in as I was passing just to let me know which sensor was playing up, I already guessed what was gonna happen, but he didn't have time to investigate.

The van will be going in for a service in the next couple of weeks (500 miles) .. This is when he will take a more in depth look, I just don't want to spill over " weekend fiddle" time into booking it in.

From what I've read the main culprit is aftermarket stereos, but not in this instance ... It just seems to be a rare fault (in any vehicle)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gilo-T5 Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 14 at 20:48
Originally posted by gregozedobe gregozedobe wrote:

Is a bad electrical connection a possibility ?  Corrosion, bent/loose pin in port (or elsewhere), or my personal favourite hate - a broken wire with external insulation appearing intact.  Worth investigating at least.

Just wondering because you did get some communication with bluetooth thingy.


I think the bluetooth and dash command just proves the obd port is working! However it's only displaying basic info which suggests there is a fault beyond the plug, maybe even the ecu itself
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 14 at 23:07
Don't know much about Bluetooth interfaces but it sounds more like a fault on the OBD socket to me. I know the Bluetooth connection worked for your Dash Command but does it rely on ign lights being on to work as most hard wired scanners do. If not, that could explain the discrepancy if it isn't using the ign fed 12v supply to the socket which could be faulty.

Also if Dash Command is using OBD 2 it will only display basic info relating to engine emissions like temps, revs, etc so only engine related things will appear.

If you plug in a registered VCDS cable there should be an amber light that quickly changes to green if the 12v connection to the socket is good so that is a handy basic first check.

Once you open VCDS on your laptop and then attempt to open a particular controller say, engine, cent conv or ABS, if there is a communication problem with that controller you will get a error message (not the one you got, that isn't a VCDS-type message) saying you have a communication problem and suggesting options.

On mine the OBD socket is a bit flaky. I have to move the connected cable up or down slightly to get a good connection (green light). So I'd check those connections first but be very careful not to short anything there!            

Edited by T5 TDI - 22 May 14 at 23:20
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gilo-T5 Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 14 at 23:56
Thanks for your suggestions T5 TDI

Unfortunately I don't have the VCDS software, or the appropriate cable. I've been relying on the equipment of my friends in the trade.
However I have a obd2 socket tester, this tests the current on all pins ( 12v power ,low current for can signals and the k-line on pin 7) I'm getting the green light on all connection.

I appreciate that asking the inter web is no substitute for proper testing.. I just can't believe my van has a one off problem.

Someone on another t5 site is adamant that the diagnostic system runs through the clocks and this causes communication issues when they have a fault, but no one seems to have solid proof or experience to a specific system/module failing and then the subsequent fix.

My friend at vw will only have so much free time to trouble shoot (at the price he charges me for weekend stuff )

I'm thinking I should just go directly to an auto electrician, but then think I should use vw experienced techs, but most dealer franchised mechanics only rely on the diagnostic system (maybe even my mate when it comes to the crunch), which doesn't work, so back to square one ..I'm not tight, I just rather not pay obscene amounts for explorative troubleshooting if I can put whoever I use in the right direction.. The fact this issue is so rare when googled doesn't give me much hope. But on the other hand I might not be giving the right people the credit/respect/trust they deserve...... My head hurts ..lol

Thanks for the input you guys have given to-date .. I haven't even intro'd myself and from joining started dumping my van woes on y'all from the off
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vwstevens Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 14 at 00:05
I seem to remember this problem on T4's with oem stereos. I think it it was just a case of disconnecting the blue wire in the radios wiring to the VW plug.... Worth a try!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gilo-T5 Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 14 at 08:10
It's defiantly not the stereo, your referring to the K-line on pin 7 of the obd port, aftermarket stereos shoot 12v back down into pin 7 which should be far lower (can-bus signal voltage - not live voltage)

I've tested for this exhaustively as this is the most common cause for communication error

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gilo-T5 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jun 14 at 18:24
Just thought I'd give a quick update, I plugged the laptop into the van yesterday as I now have VCDS lite (as I've done about 500 times before with my code reader and dash command etc) and out of the blue I had communication.. Not for long, but enough to tell me what the problem is..

I managed to get the abs fault code (which I already knew the problem to..I'm sure I damaged the wire when lowering the back end ) but more importantly it flagged up an intermittent fault with the central control module.. I didn't stay connected long enough to get the error code, but knowing there is an issue with this unit is a big step forward.



Edited by Gilo-T5 - 12 Jun 14 at 18:28
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Liquidfreak Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jun 14 at 13:21
Hey Gilo,

I was wondering how you've got on with this fault? I also have no communications with the ECU which is highly annoying. Haven't had for about 3 years now but still really keen to find out why. Not sure if it is relevant but my remote central locking hasn't worked for about the same amount of time. Though I believe that this might just be that it has lost its coding and because of the lack of communications I cannot flash the key. 

If you could keep us posted with your results that would be ace.

Cheers
Andy
2004 VW T5 Panel Van T30 2.5 130 AXD Engine
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gilo-T5 Quote  Post ReplyReply Direct Link To This Post Posted: 06 Jul 14 at 21:38
FINAL UPDATE: van fixed..woohoo!
Booked in with vw, and the communication was sorted in an hour.. It turned out the speed sensor was the problem, the fault was basically causing a short throughout the diagnostic system. Funny thing was the the abs light only came on when I lowered the van but the OBD port was failing long before that!

But hay, ABS fixed, OBD port fixed and interim service all for £280 inc from main dealer. I'm well happy

Now I can start enjoying the van
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cragz2000 Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jun 15 at 22:29
Hi Gilo T5 , hope you can help me, just bought a vw T5 and can't read error codes " link Error" comes up .
Could you please send me a contact that could help me with this issue , cheers Craig
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Toddster Quote  Post ReplyReply Direct Link To This Post Posted: 21 Dec 19 at 22:05
Hi Gilo-T5,
When you said, "It turned out the speed sensor was the problem" are you talking about the crank/engine Speed sensor? or Vehicle (ABS/Wheel) Speed sensor?
I have the same problem with my T5 Transporter 2006 Van 1.9 TDI, but I don't have a VW Dealer near where I live in Australia.
Jeff Todd
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gilo-T5 Quote  Post ReplyReply Direct Link To This Post Posted: 22 Dec 19 at 07:38
It was the ABS sensor, but as I’m on there was was another issue which was blocking OBD communication after this.. and it was the drivers door lock open/closed sensor (the switch that activates courtesy light) this is built into the lock mechanism.. it appears there there can be a number of minor electrical gremlins that can cause a headache with the OBD circuit 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gilo-T5 Quote  Post ReplyReply Direct Link To This Post Posted: 22 Dec 19 at 07:50
Originally posted by Gilo-T5 Gilo-T5 wrote:

It was the ABS sensor, but as I’m on there was was another issue which was blocking OBD communication after this.. and it was the drivers door lock open/closed sensor (the switch that activates courtesy light) this is built into the lock mechanism.. it appears there there can be a number of minor electrical gremlins that can cause a headache with the OBD circuit 

If I’m honest, in retrospect, having the abs sensor sorted was probably a freak moment of connectivity.. I’d be more inclined to blame it on the plug that goes into the door lock. Even after all this, the van has never been able to be tuned via the OBD, but at least workshop related comms worked (activating cruise control, diagnosing faulty clutch pedal sensor) 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 22 Dec 19 at 09:00
Kudos to Gilo-T5 for coming back to us and reporting in the first place and then noticing and updating on a four year old post.  Interesting stuff Gilo.  :-) 

Re the communication - As far as I know, a fault on an individual controller (engine, ABS, Cent Elec, Comfort etc) can only prevent communication with other controllers via the CAN system.  I didn't think a 'dumb' sensor like a ABS sensor could do that but I could be wrong.  If you suspect a particular controller (like the ABS pump) is preventing communication you can unplug it and see if it restores communication with other controllers.  I wouldn't do this without VCDS because it is only a test, it won't fix anything.  If other controllers are communicating ok it is unlikely to be a fault with the OBD port.

The ABS controller (which is screwed to the ABS pump) is itself quite a common fault which can cause ABS communication problems, ABS/ASR/ESP lights and wild dashboard gauge and needle fluctuations.

This is probably an example of an individual controller (the ABS pump) affecting another via the CAN system which is built in to the dash.  You can use VCDS to look at the CAN gateway (if it will communicate!) for fault codes.        

Speed sensor is just another name for ABS sensor in this case because it records road speed btw.  
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