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steve Y View Drop Down
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    Posted: 11 Aug 17 at 01:20
Hi
I have a 2006 2.5 TDI Transporter, had it since new.
I noticed awhile ago that the CEL does not light up when ignition turned on as it should.
Took the van to a vw specialist technician. They removed the instrument cluster and tested voltage inputs and said all OK Probably fault in cluster (LED or circuit fault)
I then sent cluster to a repairer, and they could not find a fault, and suggest ECM not sending signal.
The van runs perfectly, no fault codes show on scan.
If I do a self test of the instruments using VCDS scan it cycles through all cluster instuments, lights, beeps etc but no CEL. Should the CEL illuminate during this test?
If I run the van with the MAF sensor unplugged a fault shows up on the scan tool but the CEL doesn't illuminate. Should it?
I know the usual CEL problem is it coming on and staying on and some would love for it not to come on. However the van is deemed unroadworthy it CEL doesn't work
Any ideas of what I should do next?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 12 Aug 17 at 20:46
It's not part of the instruments test, or at least it isn't on my '04. https://www.youtube.com/watch?v=dzLAGwMuDIg  Start at about 0.47 if you want avoid all the exciting needle sweeps. LOL   

(Btw, if anyone wants to hear what a failing T5 starter motor sounds like, watch/listen.)  Wink 

You need to find someone who can check the signals that should be present at the dash.  However since you have VCDS you could try deliberately introducing a fault by taking say, the MAF sensor plug off and driving just to see what happens when it is supposed to actually come on in anger. 

There was a good thread here about loom chaffing behind the dash, I think that was in relation to another fault but you never know.  It seems odd that you have no other symptoms which does sound more like a dash problem.  Did the dash firm confirm that the CEL was working on their test? 



Edited by T5 TDI - 12 Aug 17 at 20:48
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stryne Quote  Post ReplyReply Direct Link To This Post Posted: 13 Aug 17 at 06:16
By "CEL" do you mean the glow plug 'coil' indicator, or the 'engine' symbol, obviously they each have different meanings, (sensor inputs, ecu outputs). But in any case it is difficult to determine from the wiring diagram how to simulate the light on, i.e. whether high or low signal, & low or high resistance signal. The 'coil' indicator could (I think?) be simulated with VCDS by operating the glow plugs. The 'engine' indicator might be more difficult, or can can VCDS operate or check the Lamda probe, EGR, dpf, etc. That wiring fault suggested by 'T5 TDI' might be as good as any place to start looking.

Just to add a bit more, if you know or find the pin-out of the instruments plugs, you could check the signal there by moving the instrument cluster out, but as always, get a trained technician if you are not sure.



Edited by Stryne - 13 Aug 17 at 06:28
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Post Options Post Options   Thanks (0) Thanks(0)   Quote steve Y Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug 17 at 00:30
Thanks for the replies
Stryne the light not coming on is the engine light not glow plugs
        I now dont think its part of the instrument test but I tried it anyway.
        I have run the van with MAF sensor unplugged and VCDS showed the fault
        but no engine light.
T5TDI    The VW techs said that the correct voltages were at the cluster but were
        a bit vague about what they were when I questioned them
        I suspect a faulty wire from ECM (if thats were the signal comes
          from)to the cluster. I cant find a wiring diagram to find which wire
        from the ECM or which pin at the cluster the signal travels .
        Any ideas re obtaining a wiring diag ?
       Maybe pull the dash out again and start looking for some chaffing of wires
     As I said originally van starts and runs perfectly
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug 17 at 11:05
It's worth checking all of the fuses however unlikely it sounds, especially no 8 and 22 in the fuse box in the cab.  But a test with a meter of all of the fuses including the ones down by the battery really is a must before you dismantle anything else.  

As I see it, the diagnostic system is on the CAN network and because of this it is in a way, connected to everything (certainly the engine controller, the convenience controller and the onboard voltage control unit.  So you can expect CAN wiring to go to the dash which should put the CEL on if a signal for a fault is received on the network.  The voltage that actually powers the CEL led may already be at the controller in the dash and you would need special equipment to be able to measure the digital can signals.    

You could try looking with VCDS at both the CAN gateway and the dash itself (which comes under 'Instruments') to see if any fault codes are there.  If you do a full scan with VCDS it should find the CAN gateway and the dash if you are not sure how to find them directly. But start with a careful check of those fuses using a meter or test lamp not just looking at them. Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stryne Quote  Post ReplyReply Direct Link To This Post Posted: 14 Aug 17 at 13:53
Yes, it appears information from the ecu to dash computing is all carried by the canetwork, (as I see it at the moment), checking continuity of the can cabling to the dash connectors might be in order, although you did mention the signals had been checked ?

T32 - 32 pin connector, blue     right, looking at rear of panel
T32/23 - Terminal 30, positive
T32/24 - Terminal 31, earth
T32/25 - Self-diagnosis/ K-wire
T32a - 32-pin connector, green     left, looking at rear of panel
T32a/4 - CAN
T32a/8 - CAN-H (convenience)
T32a/9 - CAN-L (convenience)
T32a/15 - CAN-H (info)
T32a/16 - CAN-L (info)
T32a/19 - CAN-H (drive train)
T32a/20 - CAN-L (drive train)
T32a/27 - CAN-H (out)
T32a/28 - CAN-L (out)
 the terminals are numbered on the plugs, a bit hard to make out, use a scope or a digital multimeter for measuring.
Hope this is not confusing.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote steve Y Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 17 at 02:36
Thanks again for the information
I have checked the fuses visually will do a proper test
Have done a full scan with VCDS and no faults show anywhere
You are getting a bit technical for me Stryne I dont know about testing the CAN to dash I was told by the vw tecs that all correct signals were reaching the cluster
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stryne Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 17 at 12:12
Well if they were correct then the cabling should be ok, and to me that would leave the dash controllers or the LED itself to be at fault, or maybe a dry soldered joint on a circuit board. Have a look at the pics in this thread to see what the dash insert looks like when out of the car, I would have liked more time when I had that out, to document lots more of it.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote steve Y Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 17 at 02:08
Thanks Stryne
I have had the cluster out of van a couple of times. It was sent to a company Injectronics who do repairs, to check LED, Circuits etc They could not find a fault.
I disconnected the MAF sensor again and drove around all day A fault code showed on VCDS but no light on dash, but the van ran as good as ever !!!
I would have thought I would have noticed some change in performance.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 17 at 09:25
On mine it runs ok but slightly flat.  If you ever want to check the MAF you can easily check the the expected against the actual airflow either by data logging for later perusal/graphing or watch it live on VCDS by using Vagscope.  

It does look like the fault is within the cluster as long as there are no other problems with the dash and you have no communication or other faults showing in any other controller.  I suppose it could be an ECU fault but you would have thought it would have shown up on VCDS as a missing message on the can gateway or similar.  

I think you will have to ask them to check it again with particular reference to the check engine light.  Or at least ask if they are absolutely certain the cluster is 100% since you are going to be spending money based on their diagnosis.  

Currently the CEL being on isn't an MOT failure here in the UK, are you sure about the ausssie rules? ;-) 


Edited by T5 TDI - 16 Aug 17 at 09:30
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stryne Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 17 at 13:51
@T5 TDI, when your MAF is disconnected, which dash warning shows ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 17 at 14:35
I haven't done it for years but it's only ever the check engine light.  As far as I know the glow plug light only ever comes on (as an engine management light) if the brake pedal switch is faulty.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote festa Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 17 at 07:24
Originally posted by Stryne Stryne wrote:

@T5 TDI, when your MAF is disconnected, which dash warning shows ?

It really depends on the model of engine which denotes what lights are shown on the dash.
2006 was the change over year for cat/dpf in thw uk so the earlier vans didn't have the amount of engine check lights like the later vans. t5tdi is an 2004 which is the same engine code as my 2006 which hasn't a dpf.
If I unplug my maf sensor you don't get any fault lights but it does go into limp mode which reduces fuelling and boost.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 17 at 08:37
My '04 does have a check engine light (no DPF lights of course) but it's been so long since I tried, I can't be absolutely certain if it will actually come on with MAF disconnected.  The van is too far away for me to check.  As the op has VCDS to cancel them he could take the MAP sensor wires off too!     
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 17 at 13:58
Eek!  Just retrieved my van from it's parking space and it doesn't have a check engine light!  Only the glowpug light doubling as one.  Depending on Steve's model there may be nothing actually wrong with the van!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote festa Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 17 at 17:12
The coil light does act as a warning if something is not as it should be but I've never seen a cel. My clocks do have the extra display module and will also tell me water is low or alternator workshop when that doesn't work. I do know that the later vans with the dpf fitted does have a warning light that resembles an engine outline.
I've come accustom to engine trouble on mine and never seen a light.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 17 at 22:35
Yes mine has got the display for the messages too.  Come to think of it, I can only think of a couple of faults I've had on mine that could have lead to the CEL coming on (if I had one!) in 13 years.  The brake switch failure put the glow plug light on and caused an 'Engine Workshop!' message on the display.  

Fast forward 6 years and 'Oil Pressure!' came up on the display.  I can't remember if the glowplug light came on as well because I was also towing at the time and an oil pressure warning was about as welcome as a fart in a space suit!  (Copyright Billy Connolly Smile)   But it turned out to be only the oil pressure switch faulty.  http://www.brick-yard.co.uk/forum/how-to-fit-an-oil-pressure-switch_topic92445.html If you have a 2.5 engine.

To help Steve, can anyone else who has an old model van please say if it has a check engine light, and what year, model, engine size.  To check this- if it you don't see it with all the others when you first turn the ignition on it probably doesn't exist.  You will need to cycle the key a few times to get your head around it. Smile  

The check engine light looks similar to the first yellow one here. http://www.volkswagen.co.uk/owners/warning-lights    
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stryne Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 17 at 15:05
Originally posted by Stryne Stryne wrote:

@T5 TDI, when your MAF is disconnected, which dash warning shows ?

Yeah, I was -thinking, - thinking-, "I don't reckon mine has a 'Check Engine Light' ", and when checked - sure enough, does not show, and fairly sure not a space for it. Just goes to show how attentive I was, because the cel is described in my owners manual.

It would seem it was included when DPFs were fitted, the books say the light shows for an exhaust fault. Mine does not have a DPF.

Edit: early 2005, other details below.


Edited by Stryne - 19 Aug 17 at 15:08
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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 17 at 19:42
I reckon you are right. Thumbs Up  Although, DPF equipped T5's have a DPF light which can come on (often without the CEL) if the DPF hasn't regenerated.  (Like if you have been driving around town all the time.) 


I don't know what the Aussie test consists of but if it's like our MOT, the tester will get notice of something on a particular model that is missing by manufacturers design, and therefore doesn't constitute a failure, a bit like our early vans having a CAT but no DPF.


Edited by T5 TDI - 19 Aug 17 at 19:44
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Post Options Post Options   Thanks (0) Thanks(0)   Quote steve Y Quote  Post ReplyReply Direct Link To This Post Posted: 20 Aug 17 at 08:50
Interesting
In all the time I have had the van I cant remember ever seeing the check engine light!
In fact I cant remember a fault ever occurring. It has gone into limp mode a quite a few times when working real hard but no CEL or fault show on a scan.
A while ago the hose from turbo to intercooler blew off . No lights came on just went into limp mode if not driven gently. Got out of limp by ignition off then on Ok till power needed again. Was a taxing trip home !!!
No fault lights at all but fault showed on scan
I started looking for the CEL as I was told it had to be there and it had to come on with the ignition to pass a roadworthy test if I wanted to sell the van.
After all the research I have been doing I was wondering if there ever was a CEL !! I still dont know.
Mine is pre DPF
When I ran the van with MAF disconnected I couldnt notice any difference in performance no fault lights no limp mode Just showed fault on VCDS
Thank you all for the responses
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