Page 1 of 3 123 LastLast
Results 1 to 10 of 26

Thread: [New Project Setup] How to find out/decode wiring information and pin-outs

  1. #1
    Verified VCDS User
    Join Date
    Mar 2020
    Location
    USA
    Posts
    53
    Post Thanks / Like

    [New Project Setup] How to find out/decode wiring information and pin-outs

    Car in Question: 2017 NAR VW Jetta SEL (BCM PQ25 Max3 7E0937190)

    End Goal of project: To wire a SPST switch to control DRLs. If it works, maybe even use more SPST switches to control other functionality.


    Description of current problem: I read up about relay 173 (controls DRLs) in older cars but according to erWin that relay isn't in use since July 2016. So I'm trying to find the output wire from the BCM that controls the DRL. To do this, I downloaded the Wiring Diagram from erWin using my VIN but it is 999 pages long and I (with no experience doing any of this) am struggling to find the info I need.

    Using erWin's iWire online utility seems helpful as I found the pin-out for my rotary light switch which then lead me to find that the BCM/Vehicle-Electrical-System-Control-Module is labeled in the diagrams as J519

    But how do I find the pin for the DRLs?

    https://imgur.com/a/UrlRekE



    ----------More info on project below----------------

    Project Justification: Multiple secure area checkpoints in sequence, cannot have any lights on. Holding the handbrake slightly is even more suspicious according to security personnel.

    Why not turn off with VCDS? Because I would prefer to have an on-demand DRL switch. Since DRL is BCM controlled, using VCDS would require me carry a laptop, plug in and then turn off DRL. Also, I prefer to have DRLs during normal driving so disabling them permanently is not an option for me.

    More benefits of having DRL switch: Can use easily in drive-in cinema, drive through Christmas lights parks, reaching a dark-sky village for star gazing etc.

    Other thoughts: DRLs turn off when handbrake is pulled, maybe I can wire in a switch that gives a constant to the wire to fool the BCM to think handbrake is pulled and turn off DRLs but again this would mean that the warning "Release parking brake!" would annoy the driver
    Last edited by gokarty; 03-29-2020 at 07:43 PM. Reason: added img link

  2. #2
    Verified VCDS User
    Join Date
    Mar 2020
    Location
    USA
    Posts
    53
    Post Thanks / Like
    Update: Even though the DRLs are LED from factory, they should be at the very least fused right? Since an LED with a short could pull many amps and damage the internals

    So I guess I need to also look into which fuse controls the DRLs (unless a single fuse controls the entire headlight unit)


    Edit: it seems like a single fuse guards the entire headlight unit. It's fuse 12 for the right-side headlight, Fuse 11 for left side (for HID headlights)
    Last edited by gokarty; 03-29-2020 at 08:08 PM.

  3. #3
    Benevolent Dictator Uwe's Avatar
    Join Date
    Jan 2014
    Location
    Earth
    Posts
    27,845
    Post Thanks / Like
    Blog Entries
    1
    In your other thread, you confirmed that pulling up a bit on the hand-brake kills the DRLs. I would think you could simulate that condition to the car with a SPST switch.

    -Uwe-
    Lock-down of sick people: Quarantine
    Lock-down of healthy people: Tyranny

  4. Likes gokarty liked this post
  5. #4
    Verified VCDS User
    Join Date
    Mar 2020
    Location
    USA
    Posts
    53
    Post Thanks / Like
    Quote Originally Posted by Uwe View Post
    In your other thread, you confirmed that pulling up a bit on the hand-brake kills the DRLs. I would think you could simulate that condition to the car with a SPST switch.

    -Uwe-
    Yes but then the MFD would play a tone and show warning "Release parking brake"

  6. #5
    Verified VCDS User DV52's Avatar
    Join Date
    May 2014
    Location
    Melbourne, Australia
    Posts
    3,306
    Post Thanks / Like
    gokarty: If I may intrude on your conversation - it seems to me that for your objective (i.e. to use a simple switch to control the DRL) to be successful, you must resolve the following two issues:

    First: As a basic design construct, the DRL function is not a state (of itself) that's generated directly by a physical switch. If you think holistically about the way that DRLs fit into the wide spectrum of lighting functions in a modern car, it becomes clear (to me at least) that DRLs result from the absence of night-time lighting (i.e. parking lights/low-beam). Hence my contention that the DRL function are not a lighting state in its own right -certainly not in the same way that blinkers, or main-beam, or Parking lights, or reverse lights, or fog lights are a defined lighting state that are turned-ON/OFF with a switch

    Second: At least as far as lighting is concerned and unlike in days-of-old, the BCM in modern cars acts as an intermediary: light switches become "inputs" to the control module and voltage supply to the lights (PWM waveform) are "outputs" from the BCM. It's only possible to impute a functional end-to-end circuit from a fuse somewhere to the light switch and then to the lamp - there certainly isn't a physical wiring circuit between the the three!

    What these two "confounders" mean for your project (I think) is that control of DRLs with a simple SPST switch will be problematic. At the very least, I suspect that you will need to manage multiple dependencies in your solution - which I imagine will necessitate logic-gate technology as a minimum - I think!

    Of course the other approach is to abandon entirely your search for a specific DRL -ON/OFF pin on the BCM (I doubt that the Jetta has such a pin) - and instead use the principle embedded in my "First" point above: use the ON/OFF status for either Parking Lights, or Low beam lights as a surrogate for DRL-OFF/ON respectively. But again, because of the role played by the BCM, multiple dependencies need to be resolved - I think

    Don
    Last edited by DV52; 03-30-2020 at 12:42 AM.
    VW Golf MkVII (MY13) - A3 8V hatch (MY17)

  7. Likes gokarty, Dana liked this post
  8. #6
    Verified VCDS User
    Join Date
    Mar 2020
    Location
    USA
    Posts
    53
    Post Thanks / Like
    Quote Originally Posted by DV52 View Post
    gokarty: If I may intrude on your conversation - it seems to me that for your objective (i.e. to use a simple switch to control the DRL) to be successful, you must resolve the following two issues:

    First: As a basic design construct, the DRL function is not a state (of itself) that's generated directly by a physical switch. If you think holistically about the way that DRLs fit into the wide spectrum of lighting functions in a modern car, it becomes clear (to me at least) that DRLs result from the absence of night-time lighting (i.e. parking lights/low-beam). Hence my contention that the DRL function are not a lighting state in its own right -certainly not in the same way that blinkers, or main-beam, or Parking lights, or reverse lights, or fog lights are a defined lighting state that are turned-ON/OFF with a switch

    Second: At least as far as lighting is concerned and unlike in days-of-old, the BCM in modern cars acts as an intermediary: light switches become "inputs" to the control module and voltage supply to the lights (PWM waveform) are "outputs" from the BCM. It's only possible to impute a functional end-to-end circuit from a fuse somewhere to the light switch and then to the lamp - there certainly isn't a physical wiring circuit between the the three!

    What these two "confounders" mean for your project (I think) is that control of DRLs with a simple SPST switch will be problematic. At the very least, I suspect that you will need to manage multiple dependencies in your solution - which I imagine will necessitate logic-gate technology as a minimum - I think!

    Of course the other approach is to abandon entirely your search for a specific DRL -ON/OFF pin on the BCM (I doubt that the Jetta has such a pin) - and instead use the principle embedded in my "First" point above: use the ON/OFF status for either Parking Lights, or Low beam lights as a surrogate for DRL-OFF/ON respectively. But again, because of the role played by the BCM, multiple dependencies need to be resolved - I think

    Don
    Don,

    Firstly, thank you very much for your input!

    However, I'm not sure if I understand correctly, even if the LED DRLs are controlled by PWM, there has to be a way for the car to send that PWM signal to the LED right? So the BCM would probably be the one to send that PWM via a wire right?

    Now, erWin mentions about some cars having an "LED DRL Module" but even this module needs to be getting an input from somewhere

    Another thing, so the DRLs have two different brightness modes in the 2017 Jetta, when the headlights are off, the DRLs are bright and when the headlights are on, the DRLs are still on but get dimmed significantly

    So if the DRLs get dimmed, surely the BCM has to have a connection to the LED?

    So even if it's a PWM signal, I can wire in an SPST switch to break that circuit and turn off the DRL? I would imagine this would work because otherwise how do the DRLs turn off when I turn on any turn signal, it must be that the BCM has atleast one "control wire" running to each DRL

    Your point about the light switch not being in the circuit is correct because removing every pin individually also didn't turn off the DRL, infact interesting side note, if you pull out the rotary light switch and disconnect the 10 pin harness and turn the car on, the car turns on its headlights and taillights which might be a safety feature

    Also note: When I say LED DRL i do not mean an LED bulb, the 2017 Jetta has a built in DRL strip into the headlight housing and this DRL cannot be replaced
    Reference image of DRLs : https://volkswagenofkamloops.files.w...burglights.jpg
    Last edited by gokarty; 03-30-2020 at 03:10 AM.

  9. #7
    Verified VCDS User
    Join Date
    Jan 2015
    Location
    Bosnia and Herzegovina
    Posts
    581
    Post Thanks / Like
    you misunderstood Don, in order to control DRL bcm has 2 wires (2 for positive and a ground in total 3 wires) for left and 3 wires for right module, one is +12V and other is pwm signal and ground, if you "cut" either wire pin4 or pin 10 or ground and add switch, bcm will register open circuit causing bulb out warning to appear on the dash. PWM signal i believe goes from 3v to 12v? (correct me if I'm wrong) and this controls the led brightness. So this is not an easy solution as you would think.
    What you could try to search is to turn off drl via vcds and try to wire in a power directly or by relay to wires controling drl and hoping that bcm won't be fried of course you do this on your own risk.
    There are 3 kind of services
    GOOD CHEAP FAST
    But you can only choose 2:
    GOOD and CHEAP won't be FAST
    FAST and GOOD won't be CHEAP
    CHEAP and FAST won't be GOOD

  10. Likes DV52 liked this post
  11. #8
    Verified VCDS User
    Join Date
    Mar 2020
    Location
    USA
    Posts
    53
    Post Thanks / Like
    Quote Originally Posted by m87a View Post
    you misunderstood Don, in order to control DRL bcm has 2 wires (2 for positive and a ground in total 3 wires) for left and 3 wires for right module, one is +12V and other is pwm signal and ground, if you "cut" either wire pin4 or pin 10 or ground and add switch, bcm will register open circuit causing bulb out warning to appear on the dash. PWM signal i believe goes from 3v to 12v? (correct me if I'm wrong) and this controls the led brightness. So this is not an easy solution as you would think.
    What you could try to search is to turn off drl via vcds and try to wire in a power directly or by relay to wires controling drl and hoping that bcm won't be fried of course you do this on your own risk.
    Yes, you're right about the bulb warning but that could be coded out using VCDS
    Also, the open circuit problem you mention is actually what I need because then the SPST would be the deciding factor of when the circuit is closed so it shouldn't mater if i cut the PWM or Power or Ground wire right? Unless I'm missing something?

    I would probably cut/modify the PWM wire since I'm guessing it doesn't carry too much current through it

  12. #9
    Verified VCDS User
    Join Date
    Feb 2020
    Location
    USA
    Posts
    32
    Post Thanks / Like
    Or.... you could use a dpdt to control both the left and right, tie output of your switch to its normal path. Find out the resistance of the circuit, and install a resistor to simulate it, and attach it to the other side of the dpdt switch when its in the bypass position. Just a thought.

  13. Likes gokarty, Uwe, Dana liked this post
  14. #10
    Verified VCDS User
    Join Date
    Jan 2015
    Location
    Bosnia and Herzegovina
    Posts
    581
    Post Thanks / Like
    I don't know about NAR vehicles but is it possible to add euro switch and code it so that at 0 drl is off?
    There are 3 kind of services
    GOOD CHEAP FAST
    But you can only choose 2:
    GOOD and CHEAP won't be FAST
    FAST and GOOD won't be CHEAP
    CHEAP and FAST won't be GOOD

  15. Likes Dana liked this post

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •