Just in case...is anything new? Any chance you've installed an LED center brake light or LED tail lights? If so, that could be the problem. Some manufacturers fail to add in the correct resistance to the circuit. Without it, the cruise control system thinks the brakes have been applied and it won't work...including the indicator on the cluster.

Just a thought from my own experience. :D Good luck with everything...

yes, I added an LED center brake light last night. How would that be an issue? If the brake lights are "off", no current is flowing through the system right?

Responded to your PM, Chris...

In a nutshell, the cruise control system counts on resistance in the circuit for operation - when that resistance isn't there, it shuts down. This is why, when using cruise control, the system turns off as soon as you apply the brakes. Traditional bulbs have this resistance, while LED bulbs don't...hence the problem unless the manufacturer has accounted for this in the design of the product by incorporating resistors - either on the circuit board itself, or as an outboard male/female solution for the wiring harness.

Folks more well-versed in electronics can speak better to this - I'm just a hack who's experienced the problem on a coupla' trucks over the years. :D As I mentioned in the PM, though, give your vendor/manufacturer some grief. This is a known-issue in the industry, going back at least four years now. Most quality vendors - IPCW chief among them in my experience - have addressed this with their LED designs with elegant and durable solutions.

Dido
Mine works 99% of the time, but i've had a few scenarios where I was cruising down the interstate and tried to turn it on but it wouldn't work. waited a few more miles and it finally started working.

So it turns out the Bully LED brake light I got from Stylin did indeed have a load resistor installed, yet the problem was they had installed the load resistor on the cargo light circuit, NOT the brake circuit.

So I re-soldered the load resistor to the correct circuit and now everything works fine.

As a side note, looks like this is the same issue that turns up with using LED bulbs in turn signals. The LED pulls such a low current that things just don't work right. I tested a stock 3rd brake light setup (factory incandescent bulb unit) and it pulls about 2Amps at 12Volts. The LED 3rd brake light unit pulled less than a .25Amp at 12Volts. The load resistor wired across the positive and negative leads results in the LED unit now pulling around 1Amp at 12Volts. The lower the Ohm resistor, the more Amps will move. Flip side is, the more Amps that move through the resistor, the HOTTER!!! it gets. The load resistor that came with this Bully unit looks to be about a 20Ohm, 10Watt resistor. So FYI, if you need to add a load resistor, make sure:

1- use a 10Watt resistor (I first tested with a 5Watt and it still got VERY HOT)
2- ensure you mount the resistor away from any plastic or rubber as again, it WILL GET HOT (Bully states this in their install instructions)

I know it's years later, but just wanted to thank "VroomVroom" for his input on LEDs vs regular brake light bulbs. I have a 2006 Tahoe LT, basically stock everything. 1 brake light bulb went out-in the tail-light itself, so I switched both to 2 LED bulbs, and all was good (including cruise control working) for several hundred miles. Then suddenly cruise went out - no dash indicator or anything. I found the threads about the brake light switch, and replaced that - still no cruise!!! I was getting po'd until I found this thread. I changed my bulbs back to the normal ones (which really look no different in the stock lenses), and cruise was back to normal! Thanks for keeping me out of the Stealership for messing up the cruise in the 1st place!