Troubleshooting Always On Trailer Lights When Brake Controller Is In Use

Question:

Hi, Whatever controller I use on my 2016 BMW X6 F16 , after a few use, they all adapt theirself to all trailer lights ALWAYS ON even if I shut the ignition off. Curt controller did this, ZCI Controller did the same. They worked perfectly fine right after the installation. ZCI does not forget even if I pull the fuse out. i went forward and removed ground as well to reset the device. no, it keeps the lights always on after I the fuse back in. I pulled off all the magnetic adapters on each taillight wiring, it still gives constant power to all trailer lights. - Tried 3 different ground connection locations including the battery itself. - Tried re-teaching ZCI by turning each light for 5 seconds tons of times in all possible orders. - Coded my car’s DRL to inactive. - Coded light switch auto position to DRL off. - Tried engine on, engine off, light switch at auto, at off, at on. No luck. For some reason Curt and ZCI controllers adapted theirself at giving constant power to all trailer lights even 1 hour after the ignition and the car shuts off completly. And they keep rememberring this setting. And advice will be GREATLY appreciated. Thanks in advance. Regards

asked by: John K

Expert Reply:

I would start by checking your 4-way connector, part # F4CT, and the 7-way connector part # PK12741. These wiring harnesses should be connected directly to the battery, not spliced into the wiring system. I would check this first. If everything is connected properly, I will start to troubleshoot on the vehicle side.

Whether it is a problem with the ground, a short in the wire, or rust or corrosion at a connector. It appears that your vehicle's light circuit is always at continuous power after your brake controller has been installed for a while. You will have to troubleshoot the vehicle side, a circuit tester part # PtW2993, will be needed. The LEDs will let you know if you have any issues on the vehicle side.

I have included product description links, troubleshooting links for 4-way wiring connectors and brake controllers, and installation video links below.

expert reply by: Mark Smith