eloc
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Post by eloc on Jul 7, 2024 13:26:10 GMT
Total Newbie here.
I have a 2018 Golf GTD mk 7.5 in the UK (right hand drive).
I have a problem in that only the left side tail lights are illuminated during normal daytime driving with DRLs. Eg all the front DRLs are on but at the rear only the left side (UK passenger side) are illuminated (thats both the outer and inner sections). Whereas the right side tail lights (both the outer and the inner are OFF).
If I manually force on the sidelights, (or main headlamps) then the right side tail lights also illuminate so that both rears are now lit. There is nothing wrong with the physical cluster nor the connections. It just seems that during daytime on the Auto lightswitch setting, hence when under DRL the rear left cluster is being told to illuminate and right side is not.
I would like to fix this issue, either by forcing OFF the rear taillights when under DRL, OR somehow get the rear RHS to match the rear left side when under DRL
I have an up to date rosstech VCDS but I am a beginner user. If i SCAN the car has no fault codes whatsoever.
In the CAR dashboard menu options I do NOT have any option in Lighting Settings for DRLs. Under lighting i have only the Driving on right vs left option and the early/normal/late option on automatic.
1) Has anyone seen this fault before? Only one rear lamp when daytime with DRL, yet lamp itself seems fine and lights up under other situations.
2) Any suggestions on best way to fix it? Ideally i would like the DRL option with both rears to light when on DRL but I can accept a solution where i force the rears off during DRL. I assume simplest solution would be to change a register somewhere so that rears do not come on with DRL but I might be wrong. I dont imagine that left and right rears can be set independently!
Many thanks in advance for your replies. Please bear in mind that I am a total newbie to this OBD CAN stuff and VCDS so please give an instructions in detail!!… , although I am a technical network engineer, so ought to learn from you quickly! Many thanks
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Post by dv52 (Australia) on Jul 7, 2024 21:53:07 GMT
A "network engineer" - excellent background skills as an introduction to OBD stuff !! OK, let's start with a short discussion about the main module that controls the 35 x exterior lights on mk7.5. This module is given different names depending on which diagnostic device is used - but it has a same, fixed network address on the principal CAN spine for the car - which is address hex09. If you are using VCDS, it's generally called Body Control Module (BCM) and specifically Cent. Elect. module ("J519" in the wiring diagram). The modules in this car are built to an industry standard protocol known as UDS/ODX and for a 2018 Golf, the BCM contains a database of more than 1,500 Adaptation channels that tell the module how to control various "convenience" functions throughout the car. The reason for explaining the above is because I suspect the best way forward with this odd problem is to post-up a copy of the adaptation channel database for the BCM on this car - so we can see how the right-side tail-light lamps have been programmed In VCDS speak the adaptation channel database is called an "admap" and the file is generated like this: - Ignition-ON, engine-OFF (IOEF)
- Fire-up VCDS software and connect to the dongle
- From the VCDS: Main Screen (below), select Applications
- From the VCDS: Applications screen (below), select Controller Channel Map
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- In the VCDS: Maps dialogue box (below), set-up the variables as shown:
- Press the Go button and wait for the magic to finish!
- Once the process is complete, look in the sub directory C:\Ross-Tech\VCDS\Logs on your laptop and you should find a new file with the name admap-09-module part number.CSV
- Add a copy of the admap file to a new post - as an attachment
Don
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eloc
New Member
Posts: 6
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Post by eloc on Jul 8, 2024 7:14:44 GMT
Wow. The perfect reply dv52!! This is promising! I attach the requested CSV file I modified the filename to remove my full VIN. In order to understand these maps it seems I need to speak German too! Thank you for taking the time to look at this. |
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eloc
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Posts: 6
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Post by eloc on Jul 8, 2024 9:37:55 GMT
SOLVED AND NOW EMBARRASSED !
Hi
I have found the issue and I am embarrassed to say it is unrelated to coding and I have wasted the time of you great people here!
First I thought more about the cars history..
1) HISTORY. I have owned this car for 2 months. One previous owner from new, an elderly lady who had car always maintained by VW main dealer and I have the entire VW maintenance history. So I believe noone ever manually coded/played with it. How likely is it to be coding related if noone ever manually went in there?
2) Default state for this car (I think) for the UK market would likely be that rears are programmed OFF during DRL. Thats what my previous Mk7 had. So maybe the issue is that left is somehow being forced ON rather than RHS is being forced (coded) OFF
3) The car has a nice after-market towbar. I just now discovered, by looking further back into the physical wiring loom at rear, that various signals are derived from wires heading to the rear outer clusters (not close up on the cluster which I would have seen earlier!) to drive the lighting of the tow bar. These piggyback wires are fed into a small “tow bar adaptor” box. The front end of the pcb there is a high impedance buffer so that no load is placed on the car wiring loom due to piggy backing. This CMOS buffer chip was blown and resulted in one ofmits inputs being stuck at 12v. Hence in this fault state the tow bar wiring kit (normally a high impedance input for Tail) was now sending 12v back to left cluster (input pin for tail). Hence left tail lamp was illuminated all the time. The tail on INNER cluster was also permanently ON so this suggests the inner and outer are physically wired together rather than independent.
It is interesting that this fault state (12v applied to left outer cluster tail light pin) was not causing any fault code. Although I guess any ECU probably traditionally looks more for an open circuit as a fault.
I suspect that any inspection of my CSV file will show that all my rears are coded to be OFF during DRL. BTW.. if there is a link to a past thread which shows how to change to having rears ON during DRL (is this called the Scandinavian option?) then this would be good to know since I fancy that option.
Anyway, I am so sorry to waste your time Don. By glancing around this board is clear you are a very frequent and very generous helper here. If I ever have a future VCDS issues its great to know that are such generous people out there, elsewhere on this planet, ready to assist others.
Best wishes to all and sorry again!
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Post by dv52 (Australia) on Jul 8, 2024 23:23:31 GMT
eloc : I'm absolutely delighted that you have found the problem (well-done!!)- and most certainly, no apology needed. Apart from fixing the problem, at least you learned how to generate an admap -which doubtless will be a valuable life-skill (not)  !!! Thanks also for taking the time to explain the fault cause - it may help a future forum colleague (the sole reason for forums like this is sharing information with the community) Interesting that the chip went pear-shape! CMOS devices can be suspect to high-voltage pulses, but as you will be aware -once in circuit- they are normally protected! Still, the electrical environment in a car is far from ideal and it's anyone's guess when the fault occurred. If the faulty unit is the OEM Trailer module, then it will have a network address hex69 and it's called "J345" in the VW wiring diagram. Given your description, I'm surprised that the Trailer module wasn't reported as faulty in the SCAN report for the car and/or an error message didn't appear on the dashboard (these modules are continuously monitored). If you haven't used VCDS to create a SCAN report for this car, then I suggest that you do so - see video below!
Anyway, if you want to implement the Scandinavian DRLs tweak - do the following: Note: my screenshots below are taken from past instructions - so some of my pictures won't specifically relate to the Scandinavian DRL tweak. I include the pictures below purely as an indication of the type of screens that will be encountered in the process of implementing the tweak!
PS:To operate Scandinavian DRLs - make sure that the rotary light switch is in AUTO position .
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eloc
New Member
Posts: 6
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Post by eloc on Jul 9, 2024 6:56:47 GMT
The “towing electrics module” is a very simple third party box that likely came as part of the OEM tow bar kit. It is NOT an original VW trailer module which would have become an integral part of the cars electrics. So my OEM module doesn't sit on the cars bus and it is invisible. It is nothing more than a simple buffer. A pcb which provides high impedance inputs to accept the various piggy backed lighting circuits and then has power output stages to drive these various lighting circuits on a trailer.
Big thank you for the Scandi instructions
This is a very friendly and helpful forum. At a time when the planet seems to be becoming polarised and divided, friendly helpful places like this can restore one’s faith in humanity! Best wishes to all.
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eloc
New Member
Posts: 6
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Post by eloc on Jul 9, 2024 8:49:56 GMT
PS I ran the Scandi DRL lights change as instructed, but it will not set as ACTIVE without me entering a Security Access Code. Any suggestions? i googled around and I even found your security codes lists on Ross Tech forum but I dont see any published code for this change. Attachments:
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eloc
New Member
Posts: 6
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Post by eloc on Jul 9, 2024 9:01:27 GMT
FOUND IT! 31347 is the magic number! And Scandi DRLs all working.
I need to learn do more Google searching before reposting!
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!!! 
