I noticed a trailer brake issue today on my 2015 F350 PSD with a 10K dump trailer.

I noticed that when going up hill at say 20mph and you lift entirely off the throttle and do not touch the brakes the trailer brakes will apply on thier own.

It seems to do this just as the transmission goes from second to first. At first I thought maybe the was the sway controll doing this. Turned it off still there. Then I tried getting rid of the Roll Stability by turning off the Traction controll. Still there. Could Hill Start Assist be the culpret?

This braking will last for two or three seconds and then the brakes release. By now you have your foot back into it and it is pulling hard until the brakes let go.

Sorry I don't have much more info at this time. I was on my last load of stone when the freezing rain started and I decided new truck and trailer on ice? Uh....No!

I plan on going and doing some testing with an empty trailer first and then load it if need be.

Any ideas and does anyone have a test for me to try?

 

That just sound like the exhaust brake working, it is much more aggressive on the '15 than earlier years.

 

Sorry Ltngdrvr it's not the exhaust brake. Empty, the trailer brakes will lock up.

OK I did some more investigating and found out a little more on this problem.

I turned the brake gain up to 10. Brake effort to High. Sway Controll Off and Traction controll Off for testing purposes.

Drive up hill at say 30mph with empty trailer, then just lift off the throttle and touch nothing. Trailer brakes will lock up within 50 feet. Drive flat and just before you coast to a stop the trailer brakes will lock up. Drive down hill and the trailer brakes will not lock up untill you flatten out and coast to a stop. This tells me that rate of deceleration has some effect on the sytem somewhere.

Change the brake effort to medium and everything is still the same.

Now, change the brake effort to low and everything goes away and acts the way it should, untill you touch the brake pedal. Then the trailer brakes naturally lock up as they are still on 10.

I tried lowering the brake gain with the brake effort in both high and medium. Naturally it lessens the effect of lock up the lower you turn the gain. When you finlly turn it down enough to prevent lock up you can still feel the brakes pulling down. Remember this is happening with out me touching any of the brakes. The truck is doing this on it's own.

Reset everything to high, be on the brake effort screen and have it ready to check mark the Low effort box. Drive uphill, lift off the throttle, wheels lock up, hit OK for low brake effort while sliding trailer wheels, wheels instantly let loose and roll free.

Say what?

This is what it is doing. I had the brake effort on high because I'm old school and like to feel the trailer brakes come on firm when you step on the pedal. Prolem is I am getting this without being on the brakes.

I know the easy way to fix this is leave it set on low, but I want to know if this is normal and if it is Why????

 

That does not sound normal at all.

I tow 13,000-15,000 lbs all the time. I have my trailer brake controler effort set on medium and gain on 10. Never experienced what is happening to you.

I think you may want to have your dealer look things over. Possibly change out the brake control.

 

I think something is wrong here.


Should not lock up the trailer brakes.


You will need to have a ride along with a tech.

 

Just as a suggestion if possible.... To trouble shoot Id try another trailer on your truck and try another truck with your trailer just to see if the problem follows one or the other. Could be somethings up with the trailer? Verify that you have a good ground going all the way out to the trailer brakes. I've heard of problems with electric trailer brakes that did this with bad grounds. It made the controller act as if it was set on high no mater where it was set.
But this doesn't explain the brakes going on by themselves for sure?

 

Tech ride along was to happen tonight until I had to work late. Going to do that tomorrow and the truck goes in on Friday.

I agree something is wrong somewhere. I have got to wonder if the RSL or the Sway controll is causing this even though they are turned off.

 

I'm glad things are progressing, JeffD11n. I'd like to alert your regional customer service manager so they can get involved as well. PM me your full name, best daytime phone number, VIN, current mileage, and dealership; I'll get this into their hands.

Crystal

 

Got my truck back from the dealer today and took it out for a ride with the trailer tonight. Everything is perfect.

Found out that there is a service bulletin for 2015 SD's built before 6/20/14. Basically says the TBM may send out false signal replace the unit.

 

Thanks for reporting back. Did you get a copy of the tsb by chance?

 

Sorry I did not get a copy of the TSB. I'll bet I can come up with one though. Crystal, a couple of posts up should be able to fix us up. I did PM her about her post I hope she reads this.