Troubleshooting Primus IQ Brake Controller that Shows N.C. on Display

Question

Question:

With my truck running and trailer hooked up. I am getting the . . Code on the controller, my trailer lights all work but the brakes wont. Also when manually depressing the controller it gives me the n.c. code, what do I need to do!!!

asked by: Dale S

0

Expert Reply:

There are 4 possible reasons why the Tekonsha Primus, # TK90160, is telling you N.C.

1. Trailer not connected to tow vehicle.
2. Trailer connected with open circuit on brake line.
3. Trailer connector disconnected or corroded.
4. Loss of trailer brake magnet ground.

The first one is easy enough to solve so we will go on to the second possible issue. An open circuit on the brake line or a short to the brake circuit could be caused by a couple of different issues. First, it is possible that there is corrosion or dirt in the trailer connector (see number 3 above) and that is causing a short from the 12 volt circuit to the brake circuit.

Corrosion can also build up behind the connectors where the wires attach where you cannot see it so be sure to check that as well. Check both the vehicle side and trailer side connectors.

If the brake controller checks out then you could have a problem with the trailer brake magnets. To test the brake magnets you can start with a visual inspection. If you can see the windings coming through then the magnets will need to be replaced. To further test the magnets I have included a link to an FAQ article that will help.

expert reply by: Jameson C

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Jamie M.

8/10/2020

I installed this on my truck using the adapter harness. Everything checks out on the controller. It shows n.c. when it's not connected then goes to . . When it's hooked up to my trailer, it shows .c. and when I press the brake pedal, it shows the increase proportional voltage. However, when tuning the unit with my trailer, I found that I am getting to braking from the trailer at all. This is a 5-year old trailer, so I'd be surprised if it was the brake magents. Is there a manual way to make the brake controller output a corresponding voltage so I can probe the truck 7-way connector?

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Jon G.

8/21/2020

Yup! There is that larger button on the right side of the controller that will send back power to the brakes. If you have been testing your brakes without actually traveling then that would make sense as to why you aren't getting any braking. This is because the Primus IQ # TK90160 is a proportional controller so if it doesn't sense any movement then it won't send much power back to the trailer brakes since it technically isn't needed.

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Chad B.

6/17/2020

I installed this brake controller on my truck and when I hooked my camper up it said the slide control did nothing. It then said PL . I disconnected the plug, and plugged it back in. I set to the settings that the manual said to set it at, and still nothing. After driving it went back to PL. While driving, the numbers on the brake control were bouncing all over the place. It even does it without my camper hooked up to it.

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Chris R.

6/22/2020

The "PL" error code indicates that the controller is somehow losing power. The Primus IQ receives power from the black 12V wire, so you'll need to make sure it's securely connected to the battery. If you installed the controller using a plug-in harness make sure there's not a blown fuse under the hood tied to this circuit.

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Bill I.

3/24/2020

After installing and using on one of my multiple trailers, everything worked fine with the brake controller, hooked up to one of my other trailers originally showed ‘c’ and showed voltage amount, then went to ‘nc’.Checked all connections redid all wire connections under the trailer with no avail, removed trailer plug , finally pulled the break away to test and see if there was a wiring issue or magnet problem of which trailer wheels locked up and could not even move the trailer in either direction still showing ‘nc’Only seems to be this trailer, where do I start testing

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Chris R.

3/24/2020

This is an interesting problem....as it seems like you've ruled out most of the possible causes already. You said you removed the trailer plug - did you actually replace it, or did you wire it back in? If it's the same one, inspect the pins for any corrosion or debris that might be built up inside - cleaning out as needed. Also inspect the brake output wire between the connector and where you have the breakaway switch tied in. Let me know what you find and we'll go from there.

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Christopher W.

7/25/2021

@ChrisR I installed this brake box today on a 2021 GMC Savana. I found the cables under the carpet and lined everything up according to the manuals (not colors). The only snag is that the vehicle manual said the vehicle needs 12 volt power to the engine fuse box (that is beyond me). However, I thought it would give the box set up a go. After installation the two small red lights come on and it reads NC when the side button is pushed and the number when the top button is pushed. I am concerned that it is not showing NC upon start up like the manual says it should (and did in my previous vehicle). Does a lit box mean we are good to go? I haven’t tested it with a trailer as I need it working BEFORE I pick up my camper. Thanks!

Reply

Victoria B.

7/29/2021

I spoke with my tech contact at Tekonsha today about what you're experiencing with your Primus IQ. We both think that what is happening is that your controller is not asleep when you are getting in and starting your van. The controller is supposed to display n.c. when it initially wakes up and then it will switch to showing only the . . When I shared your comment with my tech contact, he said the controller sounds like it is performing correctly.

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See All (4) Replies to Bill I. ∨

Answer 1

You will need to find out if the issue is on the brake controller, vehicle, or trailer. To test the brake controller, sever the blue wire a couple inches from the back of your controller. Then use circuit tester #PTW2979 to test the end of the blue…

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Answer 2

There are many things that can affect the voltage on the brake output wire from your brake controller to your trailer brakes such as the power setting on your brake controller, how you are testing the wire and if you are testing it with the brakes or…

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Answer 3

Although the Tekonsha Prodigy P3 #90195 and Primus IQ #TK90160 electric brake controllers are very similar they do have some key differences as well. For one the P3 is designed to work with electric and electric over hydraulic brake systems. The…

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Answer 4

If your trailer has 7 wires running all the way back to the brakes, then yes, you can tap into the existing wiring. Each of your new brakes will have two wires for the brake magnet. One wire is for 12 volt power to the brake magnets and the other…

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Answer 5

In the USA a tandem axle utility trailer with a gross vehicle weight rating (GVWR) of 7500-lbs should have brakes installed. Any trailer over 3000-lbs must have brakes on all wheels in most states, but laws do vary. Some states require braked axles…

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Answer 6

To use the Curt Echo Wireless Trailer Brake Controller #C51180 your vehicle only needs 12 volt, ground, and turn signals connected to its 7-way socket. What this means is you do not need the brake signal from the 7-way. For example, if you used a…

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Answer 7

It sounds like there is an electrical short on your trailer wiring that is activating your left rear brake assembly and that is why the brake continues to drag and get hot. Since you have swapped the brake assembly out and still had the problem you…

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Answer 8

When you disconnect or unplug a brake controller you are "reseting" it so what you are most likely encountering is an internal problem with your brake controller that once it gets reset it starts to work again till the internal problem…

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Answer 9

You are correct, you should only be getting output when the brake is applied, or the override switch is activated. It sounds like the controller might be bad, but to make sure, you should probably bench test it before tossing it. Use a circuit…

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Answer 10

Testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester like the Quickee Tester, part #PTW2993, you should get…

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Answer 11

To determine why you do not have any power on the blue brake output wire, I recommend starting at your brake controller. First, make sure the brake controller is on and receiving power. Most brake controllers have 4 wires, blue (brake output to…

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Answer 12

The controller is only putting out voltage when the manual switch is applied on the brake controller, but not when the vehicle brakes are applied, is that correct? The most likely problem is that the controller is not getting the input that the…

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