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Thread: Headlight swap: Twin halogen to bi-xenon - Do I need new CECM/BCM?

  1. #51
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    According to this, value HEX 14 would be the correct value for your byte 18.

    http://www.passatworld.com/forums/vo...-via-vcds.html

  2. #52
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    The last couple of days has been an uphill battle and I've spent numerous hours trying to get this right. Some of the behavior I cannot even explain. Let me try to recap...

    - I started out by setting the light switch to 0 with the ignition on and trying about 40 of the most promising candidates for byte 18. Not at any point did the LED strips light up so I moved on to try another idea.

    - p2trick replied to my PM and said that his code string wasn't perfect either. He only had the LED strip working on the left side during daytime. When I tested his code string I didn't notice that because my mirror was aimed at the right headlight. So I tested again and sure enough, the left LED strip lit up. It didn't take me that long to figure out that by disabling byte 24, bit 7 "Daytime Running Lights (DRLs) as Position Lights active" the LED strip on the right headlight lit up as well. On my code string that bit was already disabled.

    - By comparing our code strings I was able to determine that it was byte 11, bit 4 that had to be disabled on my own code string to get the same results as with his. Unfortunately it turned out that this bit has something to do with the high beam assistant so with that disabled the assistant did not work. Surely this must be a byte 18 issue I thought. Again I cycled the same 40 values and this time the LEDs stayed lit on many of them. However, none of them allowed me to enable both byte 11, bit 4 and disable byte 24, bit 7. It was not until many hours later that I discovered that the order of which the different bits are applied was of importance: Byte 11, bit 4 had to be enabled while byte 24, bit 7 was enabled. Then I had to apply the changes and then go back to disable byte 24, bit 7.

    - By now everything seemed to be working and I was pretty surpised when I discovered what changes had been made to the code string I started out with. None! It was exactly the same except the bytes had been applied one at a time and some of them in a specific order. Very strange I thought, I'd better let the BCM get a good night's rest and then disconnect the battery tomorrow to see if the behavior is the same.

    - After disconnecting and reconnecting the battery the LEDs no longer worked. Once again I returned to p2trick's code string to check and with that the light behaved the same also after the battery had been disconnected and reconnected. I was able to determine that by disabling byte 9, bit 4 "Personalization via Key inactive" I got the same behavior with my own code string. Finally I enabled byte 11, bit 2 "Permanent Running Light (PRL) via Low Beam active" since he had used it and I couldn't find any negative effects, and also byte 14, bit 3 "Fog Lights inactive with High Beams active".

    The current - and hopefully final - coding string is: 0002000000000000000C008C740009EC43D56588476DA5607F 80C7240041
    With all this hassle I cannot help but think that this is not really the correct coding string, but in this case maybe two wrongs have made a right. Things seem to be working and there are no DTC's.

    I now only have three very minor issues:
    - The LEDs are lit in the 0 position with ignition on: I would have preferred if all lights were OFF with the switch in the 0 position, but I do know this is by design so it's not a real problem. Byte 15, bit 5 "Parking Lights OFF with Terminal S OFF and Light Switch at Low Beam" enabled does not seem to have any effect on this.
    - No tail lights during daytime with switch in the auto position: Again, I would have preferred having tail lights also during day time, but I think this is also by design and it's not illegal.
    - Fog lights still lits up with high beam: Either I will remove the bulbs since I hardly ever use fog lights anyway or I'll keep my fingers crossed not to get fined. Byte 14, bit 2 "Fog Lights inactive with high beams active" enabled does not seem to have any effect on this.
    Last edited by bjornix; 08-17-2017 at 09:47 PM.

  3. #53
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    Good to hear that you've made some progress with that.

    Still though, some things that are odd :

    1. Fog lights should not light up with high beam. There's either a connection error somewhere or something bad with the coding string. Fixing this with the coding you made is wrong.
    2. byte 11, bit 2 "Permanent Running Light (PRL) via Low Beam active" will use normal driving lights as DRLs. It means the driving lights are on constantly. If that is not the case, again either connection or coding error. This setting should be disabled with led DRL strips.
    3. Tail lights not on with DRL => Normal. Can be fixed by finding the correct byte 18 setting
    4. DRL not off with 0 switch position. There's a setting in the setup menu found through MFD for this. Untick DRL box and all lights should go off with 0 switch position. So this is normal behaviour. But I can't remember exactly was there a bit that needed enabling to have this menu item visible or was it there if you just have DRLs enabled.

    I have B7 Passat VCDS log somewhere from my friends car. I'll try to find it. He had xenons with LED drl strips from factory. For byte 18 issue this won't help as that bits factory value is not visible, but for other codings it should be fine.

    Edit :

    Check here, someone else is also having the same issue as you, there's some tips here what to check and also some autoscans : http://www.passatforum.com/forum/viewtopic.php?t=41234 (in German but use google translate, opens it up enough to understand).
    Last edited by downtime; 08-18-2017 at 01:00 AM.

  4. #54
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    Quote Originally Posted by downtime View Post
    Good to hear that you've made some progress with that.
    No, I'm done Obviously if the value of the checkboxes doesn't match the behavior you are getting then something is off. I'm usually picky about those things, but now I'm in this with about 15 hours and I don't think I can take another 15 just to get (almost) the same exact behavior, just a little more peace of mind. I know that this may come to bite me in the ass later, but that's just a chance I'll have to take.

    Quote Originally Posted by downtime View Post
    2. byte 11, bit 2 "Permanent Running Light (PRL) via Low Beam active" will use normal driving lights as DRLs. It means the driving lights are on constantly. If that is not the case, again either connection or coding error. This setting should be disabled with led DRL strips.
    This setting does not seem to do anything for me, but on second thought I will disable it again just so the configuration matches the behavior.

    Quote Originally Posted by downtime View Post
    3. Tail lights not on with DRL => Normal. Can be fixed by finding the correct byte 18 setting
    I believe you are right and I think it's worth spending half an hour testing with some different values. If by then I cannot get it to work I will leave it as it is.

    Quote Originally Posted by downtime View Post
    4. DRL not off with 0 switch position. There's a setting in the setup menu found through MFD for this. Untick DRL box and all lights should go off with 0 switch position. So this is normal behaviour. But I can't remember exactly was there a bit that needed enabling to have this menu item visible or was it there if you just have DRLs enabled.
    Ok, I will check this

    Quote Originally Posted by downtime View Post
    I have B7 Passat VCDS log somewhere from my friends car. I'll try to find it.
    I got this autoscan from a 2011 Passat B7 with original xenons. He is Norwegian too so the light configuration should be exactly what I need (although byte 18 is of course masked). I tried to work with his coding string earlier, but didn't get any result.

    Quote Originally Posted by downtime View Post
    Check here, someone else is also having the same issue as you, there's some tips here what to check and also some autoscans : http://www.passatforum.com/forum/viewtopic.php?t=41234 (in German but use google translate, opens it up enough to understand).
    Although the discussion they are having is interesting it didn't give me much new info to work from. However, I did register that they are talking about compatible revisions of the BCM and those are all much newer than mine. Maybe the BCM I have is kind of semi-compatible, meaning it does work, but not exactly "by the book" ?

  5. #55
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    Quote Originally Posted by bjornix View Post
    No, I'm done Obviously if the value of the checkboxes doesn't match the behavior you are getting then something is off. I'm usually picky about those things, but now I'm in this with about 15 hours and I don't think I can take another 15 just to get (almost) the same exact behavior, just a little more peace of mind. I know that this may come to bite me in the ass later, but that's just a chance I'll have to take.
    I can fully understand this. When I swapped my ABS module from MK60 to MK60EC1 on the Golf. I spent three days just finding and trying the right coding and running basic settings. On second day I realized I had made an error when swapping pins on the connector. I never could finish basic settings before that as it always complained "Conditions not correct". But in the end I found the right coding and was able to run all basic settings successfully. The amount of good feeling when all the warning lights went of in the cluster was, well almost touchable
    But after that I promised to myself that I will never ever do this again (and to my wife who was nagging to me after spending two full days in the garage). Until two weeks later I was retrofitting PLA1.5

    Although the discussion they are having is interesting it didn't give me much new info to work from. However, I did register that they are talking about compatible revisions of the BCM and those are all much newer than mine. Maybe the BCM I have is kind of semi-compatible, meaning it does work, but not exactly "by the book" ?
    That as one the things I noted as well and was the tip I wanted you to read as well. I know that in Golf there are several versions of highline BCM. Ones supporting xenons and ones supporting xenons and leds. But that's just one thing.

    Take a breather and return back to the lights after few days.
    Last edited by downtime; 08-18-2017 at 03:30 PM.

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  7. #56
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    I found the byte 18 value for
    a) still have the same headlight behavior
    b) tail lights ON during daytime
    c) rear fog light working
    d) no DTC's

    That value was 91. I also disabled the PRL via low beam bit. Updated coding string is (notice I say "updated" now instead of "final" because it seems it never is ): 0002000000000000000C008874000DEC43D59188476DA5607F 80C7240041

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