I just towed my fifth wheel for the first time with my new 2010 3500HD dually. Much better tow than with my 2007 2500HD.

By setting the ITBC on 6.0 and manually activating the trailer brakes at 15 mph, the trailer brakes lock up and stop my 12,000 lb. trailer immediately. However, even with the setting all the way up to 9.0, the trailer brakes don't help the rig stop when applying the foot brake.

When I step on the brake pedal fairly hard, the truck begins to stop and the hitch bangs as if the trailer is not stopping at all. I previously used a Prodigy controller and had no problem adjusting it so the trailer brakes contributed to the overall stopping experience.

In other's experience, what should the ITBC setting be before the trailer starts helping stop the rig?

I have a 5er at 12,200 lbs that I pull. I use 4.5 and get all the stopping I want or need.

The ITBC depends on getting a signal from the pressure sensor mounted on the master cylinder to know how much brake line pressure is being applied to the truck brakes. If this sensor doesn't send the message correctly, the ITBC doesn't 'know' to apply enough power to the trailer brakes. That COULD be your problem.

I use a B&W hitch and there is very little play between the pin and the hitch - no slop. Feels like the truck and trailer are one unit. My stops are very smooth. If your hitch has too much play in it, that might contribute to what you're feeling. But I'd check out the pressure sensor before anything else.

The brake output from the controller can be checked to see if the proper voltage is being applied based on the braking conditions.

When you have the screen up on your DIC it will show the amount of braking being sent to the trailer. The harder you press on the pedal, the more bars will go across the screen. It almost sounds like the sensor that reads pedal pressure isn't working correctly.

The Prodigy is a great controller, I used one for years, but when the factory one is working, it's even better. I'm guessing something is wrong with your truck.

Thanks for the replies. I'm happy to hear that the ITBC uses master cylinder pressure to adjust it's output and not inertia or some other method. That's the way the Maxbrake aftermarket unit works and I've read that it is the best.

Anyway, I'll hitch up and check for operation in the DIC. Does the rig have to be rolling to get a proper readout?

Is there another way to test the sensing unit?

Thanks again.

I don't think you'll need a full hitch. Just connect your RV plug to your truck. Step on the brake with varying pressures and look at the DIC display of power supplied to the braking system.

Thanks for the replies. I'm happy to hear that the ITBC uses master cylinder pressure to adjust it's output and not inertia or some other method. That's the way the Maxbrake aftermarket unit works and I've read that it is the best.

Anyway, I'll hitch up and check for operation in the DIC. Does the rig have to be rolling to get a proper readout?

Is there another way to test the sensing unit?

Thanks again.


It sounds like your not getting a good signal. When you hook up you truck does it say "trailer connected"? Also, when I first hook up It says trailer connected on the DIC, then you hit the top button, just lik your scrolling through your odometer, trans temp ETC and the brake pressure things pops up. Again the harder you press the more bars should slide across.

I have a 5er at 12,200 lbs that I pull. I use 4.5 and get all the stopping I want or need.

That's funny, 4.5 seems to be my magic number also.