Brake Controller on 2005 Chevy Silverado Won't Apply Trailer Brakes With Brake Pedal

Question:

Hi there I have a 05 silvarodo 1500 and I am having issues with no brakes on trailer unless you are using the Manual override. I have checked the wires running to the box. No power being administered through the little red wire leading to box. I have a plug and play style wiring harness from gm. Now I dont know what could cause the issue. I have checked all fuses and all good. I dont know how to ckeck for power at brake switch. Is there a easy way to do this?

asked by: Lee B

Expert Reply:

Let's begin by making sure you have the controller wired to the GM brake controller pigtail correctly.

The red pigtail wire connects to the black brake controller wire
The light blue pigtail wire connects to the red brake controller wire
The black pigtail wire connects to the white brake controller wire
The blue pigtail wire and the blue brake controller wire attach together

If the pigtail is correctly wired to the brake controller, then you'll want to check the CHMSL fuse. This fuse is located in the fuse box on the driver's side of the dash where it meets the door. Because the door to this fuse box can't be seen with the door closed, many folks overlook it. I've provided a photo showing where the fuse box is located and a diagram showing which fuse to check.

If the fuse is good, the third possibility is that your brake stoplamp switch is bad. GM trucks from the mid 2000s are know to have bad stoplamp switches. The white wire exiting the brake switch (located at top of brake pedal) should show power when the brake pedal is pressed. If it doesn't, and the fuse is good, the switch is bad and would need preplacing.

I've linked you to some FAQ articles about brake controllers that you might find helpful.

expert reply by: Mike L