VW Atlas Towing - Enable 12v power always

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Prettygood

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Hi,
I’ve search but can’t find an answer. I’m trying to change the behavior of the towing functionality, from not powering the 12v pin on the 7-pin until a trailer is detected, to having power on that line at all times.

The reason is that the Curt Echo brake controller needs to be plugged in to the 7-pin on the tow vehicle first, calibrate, then have the trailer connected once calibration is complete. Since power isn’t delivered until the trailer is connected, it doesn’t allow the proper sequence for this great brake controller option. Thanks for any guidance, and happy to explore on my end if folks have ideas.
 
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Uwe

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jyoung8607

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Welcome to the forum @Prettygood!

As a (former) Atlas owner who did a fair bit of towing, I'm familiar with its towing setup and wiring. An Auto-Scan would be preferred, but scraping the memory banks here, I think there were coding tunables to set when the +12V supply pin was active. If memory serves, it was more about ignition on vs always, but I think it still relied on a trailer being detected.

That said, are you sure this really a problem? I skimmed the Curt Echo installation guide, and I don't see where it mentions anything about having to have the trailer disconnected during setup. In fact, it provides specific guidance for the opposite:

Some vehicles may require a trailer to be connected to detect a load and activate the +12V power

Troubleshooting:
Condition: LED does not light
Problem Cause: No power to brake controller, no ground on vehicle 7-way
Possible Solution: Check vehicle power and ground wiring, Trailer mode not activated for vehicle, Vehicle requires trailer to activate 7-way power


If you end up not liking or being able to use the Curt Echo for some reason, a factory towing-equipped Atlas will be prewired to accept a variety of aftermarket brake controllers. I myself used a Tekonsha Prodigy P3 with good success, and I still use it in a different tow vehicle. The required adapter harness may not be available from Tekonsha but there's at least one person custom-making them for purchase online, so it's plug-and-play with zero cutting on the factory wiring.
 
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DV52

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@jyoung8607: hmm... I'm not aufait with the Curt Echo brake controller and I'm not sure if it helps, but the OEM trailer module does have a set of software switches that determine how (or, if at all) a T30 voltage appears on the coupling - its on Byte 3 as shown (and there is a similar facility in Byte 4 for T30 voltage on pin #10.

1BO7cKX.png


Don
 
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Prettygood

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Prettygood

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Welcome to the forum @Prettygood!

As a (former) Atlas owner who did a fair bit of towing, I'm familiar with its towing setup and wiring. An Auto-Scan would be preferred, but scraping the memory banks here, I think there were coding tunables to set when the +12V supply pin was active. If memory serves, it was more about ignition on vs always, but I think it still relied on a trailer being detected.

That said, are you sure this really a problem? I skimmed the Curt Echo installation guide, and I don't see where it mentions anything about having to have the trailer disconnected during setup. In fact, it provides specific guidance for the opposite:






If you end up not liking or being able to use the Curt Echo for some reason, a factory towing-equipped Atlas will be prewired to accept a variety of aftermarket brake controllers. I myself used a Tekonsha Prodigy P3 with good success, and I still use it in a different tow vehicle. The required adapter harness may not be available from Tekonsha but there's at least one person custom-making them for purchase online, so it's plug-and-play with zero cutting on the factory wiring.
jyoung,

thanks for that, I’ve also towed with my Atlas for thousands of miles and it is very capable (2019 Airstream Sport 22’). The issue with the Curt Echo is that it needs to calibrate after being plugged into the SUV and before plugging into the trailer. I think Curt assumed 12v is present when the TV is running, and not activated once a trailer is detected. This has caused intermittent issues with the controller going from no brakes to full brakes, no progressive application of voltage as it should. I seem to have got it to work now with a specific sequence of connecting, but would resolve the issue altogether if the Atlas provided 12v power to the 7-pin anytime the car is running.
 
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DV52

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@Prettygood: With @jyoung8607 forgiveness for stealing his thunder, here's a better view of the long-code string on your hex69 (trailer) module:

Code_String to Byte_list convert
ByteHexBinary
000200000010
010000000000
020000000000
030200000010
040000000000
050000000000
060000000000
070000000000

If you compare the highlighted Byte 3 with my earlier screenshot - you can see that the software switches for T30 volts (what you call "powering the 12v pin") are set to provide this voltage in trailer operation mode. This is consistent with your description of the current behavior .

Again according to my earlier screenshot - to change this so that the T30 voltage is always available, change Byte 3 to hex 01, or Binary 00000001, or set Bit 0 =1 and Bit 1 =0 (currently Bit 0 =0 and Bit 1 =1)
Don
 
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That is great, I can see the change now. Let me try to update today and test to see if power is provided without the trailer present.
 
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Prettygood

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Ok, I’m missing something. I’m in the long code helper, found the right change, but don’t see how to accept the value and update the coding. Sorry for being fairly new. Do I need to use the security access code to enable saving the new value? If so, the access code doesn’t automatically pop up like it did when I changed the key function to roll up/down the windows. I don’t want to hit the “do it” button without making sure I’m doing it right. Thanks for the direction, I’m almost there.
 
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DV52

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@Prettygood: Don't be sorry - everything in VCDS was new to everyone here at some time in the past!!

So - I understand that you successfully navigated to the long-code helper screen below:

1BO7cKX.png


On your screen:
  • line 3) (see 3rd line down - series of black boxes) should read 02 00 00 02 00 00 00 00
  • line 4) should read Byte 3 and Binary: should read as shown

  1. From the drop-down list, select the entry 01 Terminal 30 (pin 9 power outlet),activated
  2. After this, line 4) should read Binary: 00000001
  3. Click on X on the extreme upper right side of the screen and you will return to the screen below

coding-long.png


On your screen:
  • the upper-most white box should read similar to 5Q0 907 383 L Anhaenger H27 0260
  • the value in the Current coding box (blue highlighted in the screen) should read 0200000200000000
  • the value in the New coding box (vacant in the screen) should read 0200000100000000

If so, press the Do It!! button and magic stuff should happen!

Don
 
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Prettygood

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I just hit do it and figured I could select the other setting and do it again if I messed something up. It worked as you both anticipated, and I now have 12v when ignition is on. That should be really helpful! Thanks again for the direction and I will research other cool modifications for the Atlas.
 
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