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New to the forum and thank you for allowing me to join. My Q7 came with a hitch installed but no wiring at all to the receiver. Behind the right panel and inside tire compartment I have looked for a plug. Not sure if any of the pics are the unit I need to tie into with an interface. Any help would be greatly appreciated. 2014 Audi Q7 Premium Plus, Factory trailer hitch prewiring listed in build sheet.
It's a little misleading as all Q7s are 'prewired' for the trailer brakes controller and the trailer lighting, but the actual towing bits are option items or avail as OE accessory items from dealers.
What this means in reality is that it is pretty much plug & play if you want to add the factory towing parts to the rear of car and also to add a brake controller required for heavier trailers/RVs to the front/driver's side, as a 'prewire' is provided etc. There is some coding involved if adding the factory tow controller/lighting module and harness, etc., which you can DIY via decent VAGCOM diagnostic scan tool (Ross Tech VCDS) or pay the dealership to code for you, which costs the same as you buying the aforementioned VAGCOM scan tool for yourself.
I added towing to both our Q7s. My '10 had an aftermarket tow receiver mounted (Curt) already, but no trailer lighting hook-up/harness...like your description, basically, which was good as that meant my Q7 had never been used for any 'real towing' prior.
What I did on this Q7 was bought a Draw-Tite Class IV rated tow receiver (sold the Curt receiver to offset cost), then sourced used factory tow lighting control module, new T-to-Y bolts, a NEW wiring harness from control module to the hitch, new 7-pin trailer lighting adapter/plug that connects directly to the wiring harness (where trailer plugs into) and I found a great deal on a new brake controller on clearance isle at Tractor Supply along the wiring pigtail for the trailer brake controller. I wasn't in any hurry, so just gathered all these parts after researching what was required to do it 'factory' style. I learned from that experience.
On our '15 Q7, I knew what I'd spent on acquiring all the bits piecemeal for the first Q7, and for me it made better sense to buy the OE 'tow kit' that Audi dealers sell, which is complete except you don't get the upgraded 600 watt radiator fan like the factory installed tow package provides to protect the motor oil /transmission fluid from added stress of towing.
To be clear, I didn't buy it from an Audi Stealership, but rather an online seller/storefront I found by searching on the part #, which brought the cost of the kit down considerably to around $700 USD. The beauty of doing it that way is you get the heavy-duty factory receiver, the solid shank tow hitch/ball mount & ball, which is the correct length & height tow hitch for the 4L Q7 for optimal towing, and literally everything's included...down to the T-to-Y longer bolts required by the factory tow receiver. There are directions for install and a one year warranty on the new parts, etc. It was a breeze to install after watching couple videos online of the process to remove bumper cover, and see where the 'prewire' hookups are located, etc.
Sometimes you can locate used parts as a complete set from recyclers selling online, but my advice is look at all the costs involved including shipping and don't forget about the the full programming access VAGCOM scan tool you'll need to recode your Q7s control modules for the towing addition, etc., etc. It really helps if you know what your goal is with the towing capability and then build the system, or buy the factory accessory kit that meets that defined goal.
On mine, for example, the owner prior had attached a Class III Curt receiver to my '10 TDI Q7 with no lighting capability as they only wanted to use it for a rear hitch-mounted carry tray or bike rack back there, so what they mounted was perfectly fine for that intended purpose. One thing to be aware of is aftermarket tow receivers generally use the same length bolts as the OE bumper bar, and so it is highly likely that those original bolts were reused in error when mounting the aftermarket tow receiver, especially if it were a DIY type install. Those aluminum 'stretch' bolts are deformed when torqued properly, and so can only be used once...they stretch. If you use them again, they often will snap/ break off if torqued to the correct torque spec and/or they will not achieve/hold the correct torque spec as required related to being deformed already.
FWIW:
Towing adds major stress and heat buildup, and IMHO, if you planning to tow heavy, be aware the factory tow option provides dedicated radiator fan upgrade to compensate for the additional towing stress. Suck it up and source the radiator fan/controller as either used or new OEM/aftermarket; sometimes you can get the entire towing fan shroud w/fans/controllers in it, which ends in letter code E as a new/recycled part. As new, I've seen that towing-specific, complete radiator fan shroud assembly listed for $900 by VDO. If you have a chance to buy one off a late model wrecked/recycled 4L Q7 for a good price...I'd do it, if your plans are to tow heavy trailers/RVs. It's not the Q7 won't tow them either way with gas or TDI motors, as it is a terrific tow vehicle, but it's just you are killing your transmission and other expensive components by cooking your motor oil/trans fluid, and so bad things will happen down the road, IMHO.
Good luck. Plenty of towing-specific threads on here, if you want to do some reading just search.
BTW, the factory tow harness/lighting cable connects in two places inside the car. the car's signal inputs plug (to connect to the tow lighting control module) is a red plug shown in your top pic...it's just clicked into a 'blank' plastic keeper slot with the extra wire looped around, etc. The tow wiring 'harness' cable has two connectors on it; one goes up to the tow lighting controller, and the other, a two-wire connector, branches off and that one is for the brake controller harness, which is wrapped in foam and tucked up at extreme rear of the cargo area to protect it. At front of car, the other connector end of the two-wire, brake controller 'prewire' is also wrapped in foam, and is similarly tucked up tightly to the left of driver's footrest/parking brake pedal location.
That's your towing 'prewire' orientation; so now you gotta figure out what kind of towing you need/want to do and add the correct parts set to the car. Be advised that there is a high level of integration with the factory tow setup, so for example, when you plug in a trailer, the car will sense that and change how multiple things/features function, which is why the coding of impacted control modules is very important. Some features impacted are the lane change assist/blind spot warning, park assist (adds a tow pin lineup view), air suspension level change lock-out, braking distribution mods, etc., etc. You definitely want to read in your owner's manual what systems are impacted by hooking up a trailer, and there is a sequence to follow on a Q7, especially if you have air suspension.
And lest I forget, if the trailer has LED lights as brake lights, you'll also need the Curt LED adapter, which keeps the car from thinking those brake lights are burnt out due to low voltage draw, which throws errors warnings inside the car, and will shut down power to the trailer's brake lights, etc.
It's an incredibly capable tow vehicle, but yeah, there's just a bit of a learning curve to it.
Enjoy!
Last edited by '10Q7TDI_Prestige'; May 11, 2025 at 12:25 PM.
It's a little misleading as all Q7s are 'prewired' for the trailer brakes controller and the trailer lighting, but the actual towing bits are option items or avail as OE accessory items from dealers.
What this means in reality is that it is pretty much plug & play if you want to add the factory towing parts to the rear of car and also to add a brake controller required for heavier trailers/RVs to the front/driver's side, as a 'prewire' is provided etc. There is some coding involved if adding the factory tow controller/lighting module and harness, etc., which you can DIY via decent VAGCOM diagnostic scan tool (Ross Tech VCDS) or pay the dealership to code for you, which costs the same as you buying the aforementioned VAGCOM scan tool for yourself.
I added towing to both our Q7s. My '10 had an aftermarket tow receiver mounted (Curt) already, but no trailer lighting hook-up/harness...like your description, basically, which was good as that meant my Q7 had never been used for any 'real towing' prior.
What I did on this Q7 was bought a Draw-Tite Class IV rated tow receiver (sold the Curt receiver to offset cost), then sourced used factory tow lighting control module, new T-to-Y bolts, a NEW wiring harness from control module to the hitch, new 7-pin trailer lighting adapter/plug that connects directly to the wiring harness (where trailer plugs into) and I found a great deal on a new brake controller on clearance isle at Tractor Supply along the wiring pigtail for the trailer brake controller. I wasn't in any hurry, so just gathered all these parts after researching what was required to do it 'factory' style. I learned from that experience.
On our '15 Q7, I knew what I'd spent on acquiring all the bits piecemeal for the first Q7, and for me it made better sense to buy the OE 'tow kit' that Audi dealers sell, which is complete except you don't get the upgraded 600 watt radiator fan like the factory installed tow package provides to protect the motor oil /transmission fluid from added stress of towing.
To be clear, I didn't buy it from an Audi Stealership, but rather an online seller/storefront I found by searching on the part #, which brought the cost of the kit down considerably to around $700 USD. The beauty of doing it that way is you get the heavy-duty factory receiver, the solid shank tow hitch/ball mount & ball, which is the correct length & height tow hitch for the 4L Q7 for optimal towing, and literally everything's included...down to the T-to-Y longer bolts required by the factory tow receiver. There are directions for install and a one year warranty on the new parts, etc. It was a breeze to install after watching couple videos online of the process to remove bumper cover, and see where the 'prewire' hookups are located, etc.
Sometimes you can locate used parts as a complete set from recyclers selling online, but my advice is look at all the costs involved including shipping and don't forget about the the full programming access VAGCOM scan tool you'll need to recode your Q7s control modules for the towing addition, etc., etc. It really helps if you know what your goal is with the towing capability and then build the system, or buy the factory accessory kit that meets that defined goal.
On mine, for example, the owner prior had attached a Class III Curt receiver to my '10 TDI Q7 with no lighting capability as they only wanted to use it for a rear hitch-mounted carry tray or bike rack back there, so what they mounted was perfectly fine for that intended purpose. One thing to be aware of is aftermarket tow receivers generally use the same length bolts as the OE bumper bar, and so it is highly likely that those original bolts were reused in error when mounting the aftermarket tow receiver, especially if it were a DIY type install. Those aluminum 'stretch' bolts are deformed when torqued properly, and so can only be used once...they stretch. If you use them again, they often will snap/ break off if torqued to the correct torque spec and/or they will not achieve/hold the correct torque spec as required related to being deformed already.
FWIW:
Towing adds major stress and heat buildup, and IMHO, if you planning to tow heavy, be aware the factory tow option provides dedicated radiator fan upgrade to compensate for the additional towing stress. Suck it up and source the radiator fan/controller as either used or new OEM/aftermarket; sometimes you can get the entire towing fan shroud w/fans/controllers in it, which ends in letter code E as a new/recycled part. As new, I've seen that towing-specific, complete radiator fan shroud assembly listed for $900 by VDO. If you have a chance to buy one off a late model wrecked/recycled 4L Q7 for a good price...I'd do it, if your plans are to tow heavy trailers/RVs. It's not the Q7 won't tow them either way with gas or TDI motors, as it is a terrific tow vehicle, but it's just you are killing your transmission and other expensive components by cooking your motor oil/trans fluid, and so bad things will happen down the road, IMHO.
Good luck. Plenty of towing-specific threads on here, if you want to do some reading just search.
Thank you! very informative. So, is it reasonable to think that somewhere in the rear is a module for just the trailer lights? That i can plug into and run to the already installed factory hitch? Or will I need to find a new/used module? There are other boxes back there but just didn't get pics. I believe this hitch was only for a bike rack. My trailer in just a small aluminum utility trailer with stop/tail/turn only. I've seen other google sources that say to use an aftermarket system (curt,tekonsha) behind the trim panel on the rear hatch. I'm experienced at trailer wiring and just wondering if there is a simple way to add lighting for my trailer without the extra $$$ of Audi parts and coding. Thanks for your time, greatly appreciated
BTW, the factory tow harness/lighting cable connects in two places inside the car. the car's signal inputs plug (to connect to the tow lighting control module) is a red plug shown in your top pic...it's just clicked into a 'blank' plastic keeper slot with the extra wire looped around, etc. The tow wiring 'harness' cable has two connectors on it; one goes up to the tow lighting controller, and the other, a two-wire connector, branches off and that one is for the brake controller harness, which is wrapped in foam and tucked up at extreme rear of the cargo area to protect it. At front of car, the other connector end of the two-wire, brake controller 'prewire' is also wrapped in foam, and is similarly tucked up tightly to the left of driver's footrest/parking brake pedal location.
That's your towing 'prewire' orientation; so now you gotta figure out what kind of towing you need/want to do and add the correct parts set to the car. Be advised that there is a high level of integration with the factory tow setup, so for example, when you plug in a trailer, the car will sense that and change how multiple things/features function, which is why the coding of impacted control modules is very important. Some features impacted are the lane change assist/blind spot warning, park assist (adds a tow pin lineup view), air suspension level change lock-out, braking distribution mods, etc., etc. You definitely want to read in your owner's manual what systems are impacted by hooking up a trailer, and there is a sequence to follow on a Q7, especially if you have air suspension.
And lest I forget, if the trailer has LED lights as brake lights, you'll also need the Curt LED adapter, which keeps the car from thinking those brake lights are burnt out due to low voltage draw, which throws errors warnings inside the car, and will shut down power to the trailer's brake lights, etc.
It's an incredibly capable tow vehicle, but yeah, there's just a bit of a learning curve to it.
Enjoy!
Thank you very much. My towing application will be a aluminum 12' utility trailer with stop/tail/turn only. Will I need any hardware and coding for this? No lane assists or air suspension, but I do have the sensors for parking.
Last edited by Craneop1; May 11, 2025 at 01:40 PM.
LOL, you are certainly welcome; wished I'd asked clarifying questions on your intent. Most are intending to tow pretty heavy car trailers/boats/RVs with their Q7s, so that's my viewpoint, and why I built mine the way I did.
If you are looking for nothing special, infrequent, low weight towing, then no worries; just use a bypass kit that taps the vehicles lights, like you mentioned.
If you are looking for the best setup, which will help you stay in control of the vehicle better with more frequent and/or heavier loads, as relates to the braking and other systems integration on the Q7 you get with the factory tow setup, then you can find those used online or locally; you just gotta look for them and make some offers, etc. Most recyclers know those are desirable, so they price them up...just make a lower offer, etc.
Do ensure what tow receiver is on your Q7...you mentioned 'factory tow hitch', which would be awesome if you have it, as was designed for this chassis and as prior mentioned requires the longer tow receiver bolts, so those should have been new bolts used. It is very obvious due to the chain loops are shaped very specifically and extend straight down in a U pattern; the OE receiver is also very thick, reinforced, and bulky in areas others are not; overbuilt, but in a good way.
My two cents; you can easily find the lights controller module used pretty cheaply...pay attention to the letter at the end of the part # and look up online to see the full progression of suffix letters suitable to the North American region you in. The later the letter in the progression/supersessions, the newer the part is, etc. You can easily build a wiring harness for low cost from the control module to the hitch and use the existing pass-through in the body, etc., or source a used one. There are threads that show you what you need/part #s for the connectors and body seal, etc. to make your own trailer lighting wire harness.
Overall it just depends on you and what you want to do with your Q7, but definitely read up/research the aftermarket lighting options as concerns the Q7, as this car is something 'special' when it comes to how many monitored circuits there are and the car being able to shut off power to specific circuits based on said voltage monitoring meeting expected parameters, etc.
You'll want to find out pretty quickly about what goes wrong with the 4L Q7 and your engine specifically.
The learning curve is like drinking through a firehose at first, as there's fair amount of known issues that may or not have been addressed by the prior owner(s) of your Q7, and then there's the Audi oil change guidance, and lack thereof for the driveline lubrication services. Lots to learn and manage up front as a used Q7 owner, if your intent is to keep the car long-term.
The internet search bar is your best friend.
Last edited by '10Q7TDI_Prestige'; May 11, 2025 at 03:30 PM.
Perfect info. I will do some research on used components for sure. I want to do this 1 time as I have other tow vehicles I have. Definitely factory hitch. I just think they used it as a carrier. Thanks again
My q7 came without a hitch but I picked up a factory hitch fairly cheap. I bought the new bolts from the dealer and a wiring harness and module from life-time Audi in NC for $125 shipped http://lifetimeaudiparts.com/
It wasn't terrible to install and I didn't need to use Vag-com to code it in.
Well, yeah, I mean the trailer lights will absolutely still work if you just hook up the basic components, so long as the used module you buy is already coded correctly, and you'd think it would be if buying recycled parts 'locally', right.
What you don't get if you don't code the additional control modules on the car to tell them you've added the towing is the Q7 integration factor, so that the car knows you are towing once the trailer harness is connected and it automatically adjusts/adapts what...5 or 6 related systems to be optimized for that type of use, to include turning off systems that would otherwise be quite annoying due to a trailer interfering with their functionality, etc. Will the car still tow well; absolutely. Are you missing out on some great benefits related to the towing integration; absolutely.
Choose your own path. You can read about the towing related features/impacts stuff in the Q7 owner's manual.
Oh I know how they respond when the trailer module is connected having used my buddy's Touaregs. The module was recognized from the get go and the trailer functions besides lights were functional after plugging it in. Plenty of miles traveled towing cars and no issues.
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Trailer hitch pre-wiring?
