Hi,

I installed a 7 pin trailer connector harness and a brake controller in my 2016 Cherokee Sport (KL, no factory tow package) and the car started running erratically. The first time I turned it on, Check engine light turned on and it wrote "Engine overheating" and stalled, after that, dead. I disconnected the battery, checked all the connections and tried again without the brake controller connected, this time fine. Next morning, I started the car again, it gave me multiple messages, like Service Airbags, 4WD Off (or something similar), engine fan started and switching between Rear and Drive was rough/bumpy. The problems only stopped after I removed undid the job (removing the fuses from the wires I installed) and disconnected the splice form the cold brake wire (the wire with signal only when you brake).
The CEL codes were U0140 and U0001, both related to the ECU control bus.

The install seemed straightforward, I had a 4 pin harness installed by Uhaul and I installed a 7pin adapter[1], with a Tekonsha brake controller. The install was:

From battery:
- 1 fused (20A) wire from Battery (+) terminal to 12V wire in the 7pin connector (this is the one that feeds power to the trailer battery);
- 1 fused (20A) from (+) to 4 pin harness (already installed, was working fine)

Brake controller:
- 1 fused (20A) from (+) to trailer brake controller power
[The suspect] - Spliced the cold brake wire and ran it to Trailer Brake Controller brake signal wire
- Ground into the chassi from brake controller;
- Brake controller brake output to 7pin connector brake output

After I did the job, I tested all the wires in the 7 pin connector output, all read correctly (right/left signal, brake signal, 12v, ground, etc.).

I checked for shorts, but couldn't find any (no blown fuses, nothing), the issue happened even with the brake controller disconnected, just the wiring and fuses installed, and stopped after I removed the splice and the 3 fuses from the 3 wires from batt (+). I checked the brake controller adapter (the one on the top-right in https://images-na.ssl-images-amazon....AC_SL1000_.jpg) short any shorts, but connections were fine, no short.

I suspect the quick splice I did in the brake signal wire, but I'm not entirely sure.

My last resort will be to take the car to a shop and let them double check/troubleshoot my install. I'm more than happy to provide pics on the job (which can even be a reference for future folks, as I didn't find any info on custom installs).

Thanks much!
Lucas

[1] 7 Pin Adapter: https://amzn.to/2lYIxN7
[2] Brake controller: https://amzn.to/2ktIybr
[3] Etrailer question on the setup: https://www.etrailer.com/question-382776.html?fb=yes

 

I dont remember the details, or what year (2018 maybe?), but i thought i read somewhere that when installing a tow harness when it didnt come with one already, the dealer had to send something to Chrysler and then a signal sent back to the dealer to "activate" the harness. For a flipping trailer harness lol. I dont know if aftermarket harnesses require the same bs or not, but its something to look into.

It could be something uhaul did, too. I wouldnt rule that out. Seen some bad wiring more than once.

 

The OP may have other issues too, but the dealer will have to enable the harness function.



.

 

That's interesting, I'm still slightly skeptic, as the harness is only 2 wires from the battery (+) and one from the brake cold wire, but I wouldn't doubt the car is checking for the current being drawn or something.

When I'm back at home, I'm going to check for any shorts because, interesting enough, when I removed the two fuses from the wires I installed in the battery (+) pole, the car came back to life.
I'll keep you guys posted

Cheers!

 

Sorry for the long time without replying, but a while ago I was able to make it work!

After my ECU got crazy, I decided to try again and ended up blowing a brake fuse. Darn it, I decided to spend $$$ and went to TorkLift, they told me they could install their aftermarket harness, but dealer would have to do a reset. Talked to dealer, yes, reset is possible, something like $180, but couldn guarantee it works. Ok, I would likely end up with $300 less in my walled and no one providing any warranty.
Decided to ask the dealer: can you install the harness? Yes, they could. Does the harness have brake controller? I don't know... another dealer, I don't known, and another one. They couldn't tell me if the mopar harness had or had not the brake controller, nor if it was compatible with any brake controller. Another dead end.

I decided to hack around. I noticed the cold brake wire didn't work (ECU got really weird deactivating 4x4, telling me engine overheating and all; also it exploded the fuse another time). So I decided to hook the brake controller to the center rear brake light (top of the trunk). The problem is the current would be potentially too big for both the lights and the brake controller, so I bought a set of relays [1], wired the relay low current wire to the brake light, got another 12v+ from the battery and put in the high current input. The output from the relay went to the brake controller. I tested, the relay alone, then the relay with the brake controller, all worked.

My setup, ended up being:
- 12v+ from batt to brake controller through firewall
- 12v+ from batt to relay (high current) through firewall
- relay and brake controller negative cable to metal frame
- 12v+ from rear brake light to the relay, so every time I press the pedal, it activates the relay and release the 12v+ high current into the brake controller

- aftermarket harness (Hopkins towing solution[2]) converting the 4 pin to 7 pin
- 12v+ from battery to the 12v+ to charge the trailer battery
- wire from brake controller output to the harness
- lights, turn signals coming from a 4 pin harness Uhaul installed to me

That's more or less what I did, plus a bunch of fuses to avoid blowing things (I was sort of paranoid). Now, when I connect the brake controller, every time I press the brake, there's a little click coming from the relay, which is both annoying and reassuring the setup is working . The trailer brakes worked great and I rode about 200 miles without problems with this setup.

My plan B was using one of those Curt echo brake controllers, but I found it too expensive and decided to go with my poor's man setup.

I hope this helps KL's owners, as both dealers and aftermarket people are sadly of no help... :/

Cheers!


[1] [2] [3] Tekonsha Brake Controller