OL and SH Error Codes on a P2 Trailer Brake Controller on a 2000 Ford F-150

Question:

Trailer brakes come on way too hard with light pedal pressure and the adjust wheel makes no adjustment. Also the brake hand lever does not work. It shows a top left lower case 0, period, upper case L code and a S period H codes. The trailer socket at the bumper was just replaced. There were two fuses burned and they are fine now.

asked by: Larry O

Expert Reply:

The OL code indicates overload and the SH code indicates short circuit. The two codes are probably symptoms of the same problem. Since have have replaced the 7-Way it is likely that something got crossed, miswired, or a wire is touching bare metal causing excessive power draw and a short circuit.

First, you should test the brake controller because it could have an internal error. Sever the blue wire a few inches back from the controller. Then use a circuit tester like # PTW2979 to test the end coming from the controller. It should only show power when you apply the manual override. If it has power at any other time then the controller is bad and it will need to be replaced.

If you hardwired in the 7-Way check the back of the connector where the wires attach to make sure no terminals are touching each other and repair as needed. If the 7-Way just plugs in, make sure there are no bent pins on the vehicle and connector side where they plug into each other.

If everything checks out on the truck side then the issue is certainly on the trailer. The most likely culprit is a dirty or corroded trailer connector. Cleaning it out could solve the problem. Corrosion can build up on the pins but also around back where the wires attach.

The brakes themselves could have some wiring or internal problems. Make sure that the wiring to the magnets is not exposed and touching metal and that the ground wires are attached to a clean and corrosion free bare metal surface on the trailer. Next inspect the magnets themselves. If you can see the windings coming through they need to be replaced. To further test the magnets you can follow the FAQ I have linked.

expert reply by: Michael H