How to Install Wiring Harness in 2019 Honda Ridgeline

Question:

Can you give me some guidance on how to install the 4-flat wiring harness 118778 in my 2019 honda ridgeline? it's a little diffrent than what ive seen.

asked by: Jack L

Expert Reply:

The installation of the T-One Vehicle Wiring Harness with 4-Flat Trailer Connector # 118778 on your 2019 Honda Ridgeline is a bit different because it uses a black box module, but it is still a straightforward install.

What you will need to do is connect the black box module into the 12-pin tow plug that will be near the center of the back wall of your '19 Ridgeline's cab. Once you mount that, you'll need to look under the hood of your Ridgeline and find the fuse panel and insert the included 7.5 amp fuses in Position 6 and Position 7; after that install the included 20 amp fuse in Position 9. I have added a cut out of the directions which displays this.

You then need to find the grey housing under the bumper on the driver's side and remove its protective cap; plug the towing harness into the grey tow plug and route the harness to the back of your Ridgeline's bumper.

I have added a link to a video review of this part as well as a link to the instructions for you to check out.

expert reply by: Kyle S

click to enlarge

Louis L.

4/20/2020

Just received my kit for a 2019 Honda RidgelineKit#118778 Evrything works but the running Lights. This seems to be a problem with this installation, Why cant you pinpoint where the missing connection is to the running lights circuit. I just installed the second black from you folks, and it did not solve the problem. Can you find where the missing link is, and get back tome? I dont have access to the Honda wiring diagram, or I would have solved the problem by now. Waiting for your reply, Thanks.

Chris R.

4/21/2020

We have found that some of the Ridgeline's aren't equipped with the additional factory relay that's needed for the running lights circuit. In these cases the relay - part 39792-SDA-A01 - needs to be obtained from Honda to activate the circuit.

Louis L.

4/22/2020

Do the instructions come with the relay, or do you have additional instructions to install the relay. I am ready to send back the two kits that I installed and didnt work, but if you say the relay will work, its worth a try, please keep me informed, Many thanks.

Chris R.

4/23/2020

The relay is a Honda part so you should be able to obtain it from a local dealer - unfortunately it's not something that we have available.

See All (5) Replies to Louis L. ∨

Mario

2/24/2020

I have a tester! I’ve checked connections! I checked fuses! Everything checks out! I see that others have Gad the same problem! The OEM harness comes with two relays. Is this what’s missing to make it work?

Chris R.

2/25/2020

I reached out to my contact at Tekonsha and he said an additional relay isn't needed to activate all the functions on the T-One # 118778 4-Way connector. I'm really not sure what would be preventing power to the running lights circuit, so I think it's possible that the converter box is faulty. This is something that would be covered under warranty for a full replacement.

Mario

2/23/2020

Part #118778 I just received this and installed it per instructions. Simple and straightforward. Turn signals and brake lights work but no tail lights. Ive checked connections and fuses and still nothing. Is this a defective part?

Chris R.

2/24/2020

Have you tried testing the 4-Way with a circuit tester to see if you get power on the running lights pin with them illuminated? If you are testing by hooking up to the trailer and seeing which lights work, the problem could actually be on the trailer side. If you don't get power at the 4-Way though, then the most likely culprit is indeed a bad (or missing) fuse. It looks like the trailer tail light fuse is the 7.5 amp fuse under the hood in the # 6 position. Let me know what you find and we can go from there.