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Finished the coding and I am not getting any faults but something is not quite right yet. I had 6 faults prior to the coding and I have turned on the ignition several times now without any of those faults returning. The 12-volt light on the 7-pin tester comes on immediately after inserting the tester but I am also getting a rapid sequential flash of the RT (right turn) then TM (taillights) and then LT (left turn) lights on the tester. The lights remain in this state when engaging the left turn signal or the right turn signal or pressing the brakes. The vehicle rear lights are all working properly. I do have a new light on the main console when using the left or right turn signal. It is a green light with a left and right arrow and the number one in between the arrows and it flashes in sequence with the left or right turn signal. Here is an out-of-focus photo with the new green light just above and to the left of the green left turn arrow:
Would anyone have any ideas on what I may have missed or messed up ? And should the trailer lights work properly with just the ignition on ? I did not want to turn the engine on because a neighbor was watching the tester for me. I think I will set up my camera to record the tester and turn the engine on tomorrow.
I did find a procedure for a "left/right error" after coding and I did go through the following recommended steps, but it did not make a difference:
- Ignition OFF.
- Remove connector from trailer module. (I removed the large connector from the car side, not the trailer harness connector).
- Wait until CAN-bus is in sleep state or wait 10 minutes. (I did the 10 minutes because I was not sure how to monitor the CAN-bus).
- Install connector again.
- Ignition ON.
- Press brake pedal.
I will probably try this again tomorrow but wait an hour and also remove my trickle charger. Should I just disconnect all connectors, including the 2-pin?
I think I will also try to find a different/better ground. I am using 1 of the 2 small unused painted studs and was hoping the nut thread would clear away enough paint for good contact.
Update: I went ahead and relocated the ground wire. There is another brown ground wire already mounted on the back side of the compartment. I went ahead and relocated the trailer harness ground to this same location. My original choice for ground location is not great because it is fully primed and painted, including the stud, and I did not want to grind down to bare metal. Here was my original ground location:
Changing the ground for the wire harness made no difference. I also disconnected the Q5 computer harness from the tow module overnight and performed the steps noted above and again it made no difference. The only validation I get from my 7-pin tester is the 12V input. The tester turn signal and brake indicator lights do not turn on. Could the tester be defective? I am fairly certain that the tow module is working (at least in part) because I discovered that I can not open the rear hatch when the 7-pin tester is inserted. I also discovered that I had a fault for intermittent disconnect of the tow control module this morning, which makes sense given that I left it unconnected all last night. Otherwise, I am not getting any faults with the tow module connected. I am using the Q7 harness (4L0971124F) which has an extra 2-pin connector that is not used.
I know I am late to the party but still hoping I can get some suggestions. I think I will follow up with screenshots of all the control unit changes I made on my OBDeleven. I am a little puzzled by what I am seeing with 2 control modules. Here are screenshots from OBDeleven and an explanation of what is puzzling:
69 - Trailer Control Unit
Fairly certain that Byte 00 is coded correctly, but I am surprised that there is nothing else to update on this control unit. Byte 01 & 02 show the following description "Fixed or Manually Removable" with nothing to update. The remaining Bytes (03 thru 07) have undefined bits that are all unselected.
19 - Gateway Control Unit
I selected Bit 6 under Byte 02, but when I write the change, I get a "Function Not Available" error. And thus "trailer recognition" under Gateway remains "inactive". Could this be my problem? If so, I wonder if I have the wrong tow control module installed. I purchased it used from a fellow AVS member. Another possibility is that the description is wrong and that this Bit has nothing to do with the trailer module. My understanding is that many (or all) the descriptions are OBDeleven user inputs.
Anyway... so frustrating to have gotten this far and I now have spent almost as much time with the coding as I did with installing the hitch. I will be back at it tomorrow and will grab screenshots of all the control unit changes I made.
I went through all the control units this morning with my OBDeleven to see if I missed anything but found no other trailer functions to activate. And I took screenshots of all the Control Unit changes made. Knowing the control unit Bit "descriptions" in OBDeleven can be wrong, I think my next step might be to find the Byte/Bit data from someone who used VCDS and compare to my OBDeleven data.
I did discover something interesting when using the 7 way tester, namely the 7-way output is active even with the ignition off. The tester was still showing a 12V output when I turned off the ignition. Another odd behavior with the tester inserted is a fairly loud ticking sound coming from the tow controller about every 4-5 seconds. This sound coincides with a rapid firing of the RT, TM, LT lights on the tester. Again, I get this behavior with the ignition on or off. Is it normal for the 7-way output connector to be HOT even when the ignition is off ??? I ordered another tester and my next step might be to find another tow controller but I really hoped I was done spending money on this hitch set-up.
Here are all the controller unit screenshots: 01 Engine_05_Bit 4
03 Brakes_01_Bit 7
03 Brakes_02_Bit 6
5F Multimedia_10_Bit 5
6C Rear View Camera_Changed Value from original 1020010
09 Central Electrics_18_Bit 5
19 Gateway_Fail_02_Bit 6
46 Comfort System_12_Bit 5
69 Trailer_00
69 Trailer_01
69 Trailer_02
Hopefully this might help anyone else late to the party and working thru coding issues. Keep in mind that my 2014 is Premium Plus. If you have a Prestige, there may be updates required for other control units like lane change assist or adaptive cruise.
I pulled out my Fluke multimeter and discovered that I am only getting a little over 1 Vdc output from the connector and a slight voltage pulse. And yet my tester 12V indicator lights up. Given this and the ticking sound from the control module, I am really starting to suspect that the output of the tow control module is bad. Another possibility is a missing fuse and/or relay. As I am sure is the case for most users in this thread, my Q5 was not previously wired for a hitch. Did anyone have to add a fuse and/or relay to get the electrical working?
Update:
Amazon just delivered the new 7-way tester. The new tester shows that the turn signals work fine and it does not create the ticking sound I was hearing from the module when using the other tester. I still need to have my neighbor friend drop by to check on the brake function, but I am so relieved. I suspect this new tester has more internal resistance built in and properly triggers the module. Ultimately, I really need to test it with a real trailer light package.
Problem solved. See above. It was the damn tester.
However, I would still love to get some feedback as to why I am not able to write the trailer recognition code for the Gateway (19). Also, there was one part of the coding instructions that I could not find in my OBDeleven app. For the 69 Trailer control unit, instructions specify entering "12345" in the WSC field, "444" in the Importer field and "00001" in the Equipment # field. These may be VCDS specific inputs and perhaps it is does not matter if everything works properly. And I won't really know how well it works until I hook up a trailer. Time to buy a utility trailer and a fishing boat with trailer.
Glad that worked for you but not sure I want to screw into the fender even with a tiny screw, given my Q5 resides in Wisconsin. Anyway, I came up with a fix using the fiberglass tape and aluminum foil. I wrapped an H-shaped piece of fiberglass tape around the top and bottom of the slot and then glued it down with super glue (epoxy may be better but the super glue was easier to work with and faster setting). I immediately placed a piece of aluminum foil over the glued area and clamped it. After about an hour, it set up well and seems to be quite rigid. It may only be a one-use solution but hopefully I don't need to take the bumper cover off again. I also greased the 5 tabs on each side with a little silicone to help ensure the bumper snaps into place without too much effort given the slots are a little thicker now. I should know how well it works tomorrow.
As for the extra forward slots in the older version of the Stealth receiver, I made the decision to utilize this attachment point even though Stealth said it will not make a difference in towing capability. I agree that it is redundant, but I did not like how the 4 original bolts held up to torque when I re-installed them. Both the bolts and the captured nuts in the frame were rusty. I cleaned up the bolts with a wire wheel but I wish I had ordered new bolts. I may check to see if these bolts were originally "torque to yield" which might explain why I felt the torque begin to drop off as I approached 40 ft-lb. The spec was 45 ft-lb but I only went to 40, in part because I applied Loctite beforehand. It could be the bolts are fine but it is the rusty captured frame nuts that are not holding up well to the torque. Here is a photo showing the extra hole which is covered up by the small gray square of tape. The bolt installs here and goes clean thru the frame and will be secured with a locknut on the underside of the frame, near the exhaust pipes. It will just give me a little peace of mind.
If you used the original 4 bolts that were holding in the aluminum impact bar, you need to replace those before you use your hitch for anything more than a bike rack. Those bolts don't have the correct strength rating for the tow bar. The correct bolts are actually slightly thicker as well (they still have the same thread size and pitch obviously). You don't have to necessarily buy the expensive Audi black bolts though. The bolts I got for mine were actually listed as genuine BMW bumper bolts for an X6 or X7; they just need to be the same length, thread size, and strength as the required Audi part.
If you used the original 4 bolts that were holding in the aluminum impact bar, you need to replace those before you use your hitch for anything more than a bike rack. Those bolts don't have the correct strength rating for the tow bar. The correct bolts are actually slightly thicker as well (they still have the same thread size and pitch obviously). You don't have to necessarily buy the expensive Audi black bolts though. The bolts I got for mine were actually listed as genuine BMW bumper bolts for an X6 or X7; they just need to be the same length, thread size, and strength as the required Audi part.
I do not believe that is true, at least not for my 2014 (and I assume other B8.5's). The OE bolts were grade 10.9 based on the head markings, same grade as those supplied by Stealth. The OE bolts did have a slightly smaller body diameter compared to those supplied by Stealth but not enough to make a significant difference. I have seen the same unusual bolt design that Audi uses with control arms where the body diameter appears to be the same as the root or pitch diameter of the threads, rather than matching the major diameter which is more typical. Anyway, I did end up using all 6 of the bolts supplied by Stealth for 2 reasons. First, the larger body diameter equates to less slop/play. Second, the OE bolts were rusty.
Also, I did research and discover that the OE bolts are not torque to yield. I think the "mushy" feeling I was getting when tightening the bolts was due to some springiness in the frame rail and also possibly the rusty captured nuts in the frame rail.
And to clarify, my Stealth receiver is the old 1-piece welded design. The newer Stealth receiver is a 3-piece bolted design. I had the newer installation instructions and I initially thought the hardware provided by Stealth was for assembly of the new 3-piece receiver because the newer instructions called out re-using the OE bolts to install the receiver. But then I realized the 6 bolts provided were the same thread spec, length, and grade as the OE installation bolts. I asked Stealth for the old installation instructions, which confirmed that the 6 bolts provided were indeed intended for the installation of the older single-piece/welded receiver. The Stealth rep explained to me that they did not initially know the grade of the OE bolts and that is why they provided new 10.9 bolts for the installation. They later were able to determine that Audi was also using grade 10.9 bolts and then updated their instructions to re-use the OE bolts.
I purchased via ebay:
1. Genuine OEM VW / Audi Trailer Hitch Detection Control Module 8K0907383E ($150 Shipped)
2. Genuine OEM Audi Trailer Hitch Detection Control Module Bracket 8R0907297A ($60 Shipped)
3. PORSCHE MACAN TRAILER HITCH TOW IMPACT BAR 2019 2020 2021 2022 8R0800491A OEM ($450 shipped)
4. NEW AUDI Q7 4L TRAILER OPERATION WIRING SET FOR SOCKET 4L0971124F OEM ($300 shipped)
That last one hurt, but I really didn't feel like making a wiring harness from scratch.
Also, via Amazon:
"POLLAK (11893 7-Way RV OEM Socket" $20 shipped. I tried the multi-4pin+7pin, but it didn't fit, wasn't modifyable on the plastic-side (too thin) and I didn't feel like drilling steel.
All parts worked perfectly. The Q7 harness has an extra unused single-pin plug on the control-module side. Additionally, it's grommet was way improperly positioned for my Q5 - used a bit of dish-soap-water to lube the wire up and slide it appropriately. Don't fasten anything until you've got the control module in place, and the side-door wired back up, because you'll want to make sure you have enough slack. I had to unbolt the fuse box in the rear-right of the car in order to get at the bolt holding the bumper on there. Turns out when I had my reverse beepers serviced a few years ago, they totally !@#$ed the clips holding the bumper on near the tires, so those were already broken before me. It was funny taking out the 5lb aluminum and replacing it with 40lbs of steel (or whatever the actual numbers are).
I believe in terms of tools, I used the following:
3/8" Torque Wrench
3/8" Socket Wrench
10mm deep sockets (has to go over a 1.5" stud)
Socket extensions (for that pesky bolt behind the fuse box)
Screwdriver with T25/T30/philips bits
Mini-bit-holder-ratchet for the T30 I believe.
Plastic Pry Tools
Ratchet was only needed for the 17MM bolts holding the hitch itself on. I used a mini-ratchet with the torx bit for the torx screws in the rear-wheel-well. There is not enough space for a screwdriver, but I had a mini-ratchet in my Vehicle-EDC that I used with a torx-bit to get those screws.
Some notes:
As soon as I turned the car back on, TSC, TPMS and auto-start-stop showed errors. After programming (generally followed the guides listed, with the help of Wei @ VacComRental in Palo Alto CA), the alarms all disappeared. However, I initially couldn't tell if anything worked! Voltmeter will read ~1 volt on all the pins, and my tester just flashed all lights at probably 10Hz. I had to go to U-Haul and plug into a trailer to validate that it actually worked. Lights worked, MMI showed a ghost-trailer behind the ghost-car when in backup camera mode.
Some context: I've literally never taken a bumper off in my life. I've done minor car electrical work but this isn't even that. It's really easy. If I was efficient and didn't second guess myself, I'd say I could do it in 2 hours. Probably took me 4 hours combined, partly due to working in a gravel driveway, and partly due to working at dusk!
Did you do anything to repair the !@#$ed bumper clips? Funny that I had the same issue due to the bumper repair done by my local Audi dealer years ago. It's better now after my drywall patch repair.
05-22-2024, 02:34 PM
