Troubleshooting PL and SH Codes on a Tekonsha Primus IQ Brake Controller
Question:
I have a primus iq brake controller and it doesnt wwork. I keep getting a pl. And h errors , could you explain them to me ? It is on a 2009 gmc sierra 1500 and is used to pull my trailer for the most part , but with 13000 miles i dont see it wesrimg out. Can you help me ?
asked by: Marvin H
Helpful Expert Reply:
The PL error code on the Primus brake controller # TK90160 indicates that power is interrupted when stepping on the brake pedal. Check the connection of the red wire. It should be attached to the brake switch wire that has power only when the brake pedal is pressed. If it has power at any other time then it is not the correct wire.
The SH code that you see on your Tekonsha PRIMUS IQ brake controller indicates there is a short somewhere on the brake output circuit when idle, or when the brake pedal is not being pressed. Tekonsha states that this issue can sometimes be caused by some test lights if you are using test lights. To troubleshoot this issue, start by disconnecting your trailer and inspecting the trailer and vehicle side connectors for corrosion build up and clean or replace parts as needed to see if that fixes the issue.
If that does not resolve the issue, then use a circuit tester, like part # PTW2993, to test the brake output pin on the vehicle side trailer connector (the pin in the 5 oclock position) for voltage when the manual override is activated. If you do not have a signal on the brake wire pin, then cut the blue wire about 6 inches back from the brake controller and test for signal at that point. If you do not have a signal there, then there may be an internal issue with the brake controller and it will need to be replaced.
If you do have signal at that point, then inspect the brake wire between the brake controller and the vehicle trailer connector. This will be the blue wire coming from the brake controller. Check for any pinched, frayed or damaged sections of wire that could cause a short. If you have factory installed trailer wiring, then inspect as much of the wire that you can see.
If the SH code appears when your trailer is connected, then there could be short on the brake wire on the trailer. First, inspect the ground connections for the trailer connector and the brake assemblies. A poor ground connection can cause many issues. If the ground connections are okay, then inspect the brake wire between the trailer connector and the brake assemblies for any pinched, frayed or damaged sections. If you do not find any issue with the trailer wiring, then you may also want to inspect the trailer brake magnets for abnormal wear. If you can see the copper windings on the surface of the brake magnets, then I recommend replacing the brake magnets.
I have attached a wiring FAQ article along with the installation instructions for the brake controller for you to check out. This article should prove helpful when troubleshooting your trailer wiring.

Products Referenced in This Question
Product Page this Question was Asked From
Tekonsha Primus IQ Trailer Brake Controller - Up to 3 Axles - Proportional
- Trailer Brake Controller
- Proportional Controller
- Electric
- Automatic Leveling
- Under-Dash Box
- Dash Mount
- Up to 3 Axles
- LED Display
- Up to 90 Degrees
- Tekonsha
more information >
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