Troubleshooting OL and SH Error Codes on Tekonsha Primus IQ Trailer Brake Controller # TK90160

Updated 07/09/2025 | Published 06/15/2015

Products Featured in This Question

Tekonsha Primus IQ Trailer Brake Controller - Up to 3 Axles - Proportional

(2159)

$90.04

Digital Multimeter with 42" Long Test Leads - LED Display

(3)

$22.17

Question:

works okay for the first few seconds of braking, then goes to oL then to SH code, after awhile will start operating again with the same problem. please advise me of the most likely areas a bad connection could be or maybe its the controller? thanks

asked by: Leon H

Expert Reply:

Both the OL (overload) and SH (short) error messages on your Tekonsha Primus IQ Trailer Brake Controller # TK90160 tend to suggest that either your trailer has too many brakes for the controller (6 are the maximum) or that there is a problem in your trailer's brake circuit wiring. You can start by inspecting both the vehicle and trailer connectors for any signs of corrosion or trapped dirt that could cause two circuits to become bridged together. Check both sides of each connector and clean/replace as needed.

Also check the trailer's entire brake circuit wire from the trailer connector all the way along the wiring (looking for signs of cracked or worn insulation) back to each brake assembly. If the brake circuit wire has any damage this could cause a short that would lead to the overload and short circuit error messages. Repair or replace any damaged wire.

If no wiring problems are found you can test the brake magnets themselves by following the procedure outlined in the linked article. You will need a multimeter like # PT89ZR. If you do find your magnets are worn we offer replacements that can be viewed on the included link.

expert reply by: Adam R

Mark H.

7/9/2025

Im having this same problem, the codes come on for a bit then the controller works but it will eventually do the same thing again. I tested the power to tow vehicles 7 pin with the power boost engaged on controller and I get 10 volts,is that good enough ? Thank you for your time Mark

Jameson C.

7/9/2025

@MarkH That sounds like an intermittent short on the brake output circuit. This is probably due to a cut or exposed wire that is bouncing around and shorting out. So what you'll want to do is go over the output circuit on the trailer side of the wiring and see if you can find any issues and fix as needed. Also check out the pins of the 7-way for corrosion and sand as needed to clean them off.