Rochelle
When you say factory installed controller, I assume you mean the ITBC system the GM has used for several years. I have that on my truck and it is a great controller.
You must manually set the gain. The higher the number the more voltage that will be supplied to the trailer's brakes. My trailer is about 12K and I set my controller at 5 and that seems to work very well. In a few cases where roads were steep and the traffic was heavy, I bumped it to 6. I wouldn't be surprised if 4.5 weren't exactly correct for your truck. Experiment with your setting,a little more, a little less (maybe 3.5), and see what the difference is. As you step on the brake harder and harder, you should see the DIC indicator move from left to right, showing that more and more voltage is being applied to the trailer brakes. When you think you have the correct setting, make a couple of emergency stops and see if you have the control you need. Of course, find the place to do this that doesn't have traffic to interfere with your testing.
As for smells, it is possible that there are some brake problems on the trailer itself. New brakes smell more than old brakes. but you should be beyond that by now. First thing I would check is to make sure that your emergency cable hasn't been pulled and the brakes are being applied all the time. (I doubt this would be the case, but check just to be sure.) Second would be to have someone check the adjustment of the brake shoes. A trailer sales place (not an RV place) will likely be the cheapest and most experienced at this task. They can also check the function of controller and the brakes together, including checking the trailer's 7-way connector to your truck. It certainly is possible that there is a short from a battery+ wire to your braking system and that would also be part of the check.
Another way to help sort out the problem is to use an infrared temp sensor to measure the temperature of each of your trailer hubs after you've stopped a couple of times. These temp sensors cost something less than $20, they have a laser pointer, and a readout of the temperature where the laser hits the object. The sensors is a great tool for everyone who tows a trailer. So easy to check hub temps when you stop for fuel. Your trailer hubs should be withing 15 to 20 degrees of being the same. If you see one that is substantially hotter, BINGO! you have found where the problem is. Just need to determine the cause.
