Expert Answers about GMC Acadia

• No Brake or Turn Signals With Trailer Wiring Harness On a 2007 GMC Acadia
• I am not sure which exact trailer wiring harness you are using but if you have one that plugs into the factory tow package plug like the T-One Vehicle Wiring Harness part # 118384 for example then the issue you are having would lead me to believe that you are missing some fuses/relays or they are blown. I took a look in your owner's manual and it lists two fuses for the stop/turn signal lights, "LT TRLR STOP/TRN" for the left stop/turn circuits and "RT TRLR STOP/TRN" for the right stop/turn...
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• Troubleshooting Trailer Brake Lights and Turn Signals Not Working After Installing 7 Way on Vehicle
• If you've just installed a 7 way connector like the # ETBC7, you'll want to start by testing the plug on the vehicle using a circuit tester like the # PTW2979 to make sure that each pin is operating properly; you can refer to the photo attached or a helpful article that I've linked for information on testing the circuits. I would also recommend making sure that your ground wire on this harness is firmly grounded to a paint and rust free spot, as ground wires are the most common cause for...
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• Hardwiring Brake Controller to 2017 GMC Acadia Troubleshooting White and Blue Wire Not Active
• Does the third brake light of your 2017 GMC Acadia still activate? Normally if the stoplight circuit on a GM vehicle stops working the issue is a blown third brake light fuse. The white wire with the blue stripe on a 2017 Acadia is supposed to be the stoplight circuit. I'd be willing to bet the fuse is just blown.
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• Troubleshooting Tekonsha T-One Trailer Harness Not Working on 2012 GMC Acadia
• The Tekonsha T-One Wiring Harness # 118451 that you ended up installing is the correct harness for your 2012 GMC Acadia and it will work whether or not you have the tow package so you made the right choice there. If you happen to have your trailer on hand, the first thing I recommend doing is simply hooking it up to the Acadia and plugging in your connectors. Sometimes those LED testers can be a little finicky so it's possible that the harness works perfectly and the tail lights on the...
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• Troubleshooting Brake Controller Installation For 2013 GMC Acadia
• I would start by checking to make sure each wire is connected in the correct location by function not by wire colors because colors can vary. Next, I would make sure ground wires are firmly connected and secured. After that, I would check all your wires with a circuit tester like Item # PTW2993. Finally, I would double check fuses and relays to make sure they are working. I am attaching articles on brake controllers and troubleshooting that might help.
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• Troubleshooting No Trailer Turn/Brake Signals with 2007 GMC Acadia
• I do agree that the wiring issue you are experiencing is somewhere on your Acadia. You mentioned that the Acadia didn't come with the tow package but it does have the trailer wiring and hitch. This means you likely have a T-Connector wiring harness installed such as the Tekonsha # 118451 that plugs into factory ports behind the tail lights. What I recommend doing is checking the white ground wire coming from the harness. Make sure this is still securely attached to a clean, bare metal...
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• Troubleshooting Trailer Connectors That Do Not Pass Running Lights or Turn Signals
• The best way to troubleshoot trailer wiring is to first test your Acadia's 4-pole WITHOUT the Curt adapter. This will let you know if the signals are reaching the adapter. Even though the LED test lights may come on, since these take so little power to light up it could be that there is a small residual voltage in the system that is causing them to illuminate even when no actual running light or turn signal is reaching the adapter. You can use a tester like the # PTW2993 to check the Acadia's...
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• Troubleshooting No Power On T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118451
• I would start checking fuses and relays on the power block in the engine bay. The cover should have a map or listing of all the fuses. Check all of the fuses that have anything to do with taillights or tow circuits. I have added a link to a wiring FAQ page that shows which pins should serve which function. Use the circuit tester like # PTW2993 to make sure everything is on the correct pins.
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• Constant Power on Pins Inside 4-Way When Installing T-One Harness on a 2015 GMC Acadia
• I spoke to my contact at Tekonsha about the issue you are having with the T-One Vehicle Wiring Harness part # 118270 on your 2015 GMC Acadia. They said they have heard of this issue before but it is not very common. For starters, you will need to switch the orientation of the relays if they do not look like the ones in the attached photo. Unlike most relays, the pins are positioned in a way that will allow them to be installed incorrectly so you will need to check this first. If the relays...
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• What Circuit Does Red Wire of Brake Controller Attach To
• I would hammer a little harder on what circuit they attached the red wire to of the brake controller. It was supposed to attach to a circuit that only has voltage when the brakes are applied. If they attached it to a random circuit and didn't verify it had voltage that would definitely be why.
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• Tekonsha P3 Installed in 2014 GMC Acadia Won't Power Up
• Check the fuse box in the engine compartment, it's on the passenger side. Remove the cover, and look for the fuse location labeled '*' or 'TRLR BRK' as shown in the diagram I've provided. Install a 30 amp fuse or replace it if it's blown. I think what might have happened is that although your OEM brake pigtail might have the same wire colors except for the gray wire, the wires do NOT match up color for color to the brake controller wires. On your pigtail, the red wire is for 12-volt power,...
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• Tail Lights on 2008 GMC Acadia Stop Working when Trailer is Connected
• Let's start with the easy stuff. Make sure the white ground wire on harness # 118451 is attached to a clean bare metal surface on your 2008 GMC Acadia. There can be no coating or paint and it works best if the wire is grounded by itself. If that doesn't help then what is probably going on is the trailer lights draw more power than the vehicle wiring system can handle. You can test this by removing the connections to some of the lights. Then, if everything else starts working, including...
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• Trailer Lights Malfunction on a Small Utility Trailer Behind a 2009 GMC Acadia with Factory 7-Way
• Vehicles with LEDs will have problems with standard trailers unless a powered tail light harness is used, or there is a factory tow package. If your 7-Way on your Acadia is indeed a factory connector, you should have no problems with LEDs vs. incandescent lights. Most small utility trailers do not have a 7-Way. 7-Ways are used on larger trailers that have electric brakes, or hydraulic systems powered by a battery, or boat trailers with hydraulic actuators with reverse lockouts. If your...
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• Troubleshooting Trailer Turn Signals Malfunctioning with 2007 GMC Acadia with 4-Pole Wiring
• The problem you describe, both trailer turn signals activating when either turn signal on the Acadia is engaged, is typically a grounding issue. Since you have already re-worked both the vehicle and trailer main grounds to ensure both are solidly connected to clean bare metal surfaces, then the most likely cause for the problem is either a bad wiring harness on the Acadia or some issue with your adapter. I could not find purchase history to let me see the specific wiring harness and adapter...
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• Why Do The Arms Of My Roadmaster Nighthawk Tow Bar Keep Falling To The Ground
• The Roadmaster Nighthawk All-Terrain Tow Bar w/ LED Lights # RM-676 has a Locking tab up top that prevents the arms from pivoting down fully to the ground. If you don't fold the arms up and get the locking tab nut in the hole in the locking tab and then fold the arms down to either side the pivot point will allow the arms to fall all the way down. Having played with this before I can say it is a bit of a pain to get he pivot point lined up exactly to the locking tab perfectly so you might...
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• Blown Fuse on a 2020 GMC Acadia Causing Wiring Harness Malfunction
• It sounds like you are either missing a fuse or have blown it out. You are looking for fuse F11 in the rear compartment fuse box of your 2020 GMC Acadia. This would cause the reverse function to go out but not the other ones with the Tekonsha T-One Vehicle Wiring Harness for Factory Tow Package - 7-Way Trailer Connector item # 118276. I have linked a picture below that will help you find the fuse location. This fuse box is in your rear cargo area on the driver's side.
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• Troubleshooting No Brake or Turn Signal Lights On Trailer Wiring Harness of 2013 GMC Acadia
• For your 2013 GMC Acadia, the T-One Vehicle Wiring Harness for Factory Tow Package - 4-Pole Flat Trailer Connector # 118270 and similar wiring harnesses require installing the relays and fuses, so I recommend checking those locations for a bad relay since you have already checked fuses and wires. I've attached a video to assist. You can use a circuit tester like # PTW2993 to check each function of your trailer wiring without a trailer connected to ensure function and isolate your possible...
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• Trailer Lights do not Work with the Tow Ready T-One Harness # 118451 on a 2010 GMC Acadia
• The Tow Ready T-One Wiring Harness, # 118451, does not require any additional fuses or relays. As you said, this harness provides power to the trailer lights from the vehicles tail light circuits. The only time you would need to install a fuse is if one of the taillight fuses were blown on the vehicle. This would mean your taillights, turn signals or brake lights were not working on your Acadia. If you are positive that you have a good ground and the T connectors are installed correctly...
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• 2009 GMC Acadia LED Turn Signals Operate Erratically After Installing OEM Trailer Wiring
• I have not heard of this issue before on an OEM part installed on a vehicle. Usually if this happens it is on the trailer and is usually a ground problem. I am not sure how the OEM harness installs but if it has its own ground wire then make sure it is attached to a clean bare metal surface. No paint or undercoating can be present. Also, it really should be grounded to its own location and not share a common ground with other electrical devices. It is possible that the trailer lights are...
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• Why Won't the Mounting Bracket on My Curt Hitch # C13293 Fit My 2020 GMC Acadia?
• I'm sorry to hear about your hitch! Given that your vehicle is a non-AT4 model 2020 GMC Acadia, one of the common issues people have with hitches is bending/bowing of the hitch during delivery. If the angle on the welded end of the driver's-side brackets does not match the frame rail, it does indeed sound like an issue with bending/bowing of the Curt Trailer Hitch - 2" # C13293. While we have not heard of the # C13293 not fitting your vehicle, bending/bowing is more common than people...
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