Sudden jerks from trailer brakes

[Philip]

Originally Posted by brulaz

I believe that stability control and traction control and ABS are all different things.

No idea how stability control works, but it was initially used for roll-over protection in SUV's, but now can be found in many vehicles. Stability control uses all sorts of info, including "wheel speed, throttle position and steering wheel angle sensors, yaw rate and lateral acceleration sensors, and a gyroscopic roll rate sensor."

Apparently new Ford trucks have integrated their built-in brake controller with their stability control system so that if a trailer starts to sway, it is detected by the stability control system (somehow), and the trailer brakes are applied. Here's a pdf found via google: Ford Trailer Sway Control
And here's the video:

It amazes me the technology they're putting in vehicles these days. I just wish the trailer's themselves would catch up.

Hello Bruce,

Thank you for the information. Very interesting. You are right - they keep adding ever more sophisticated controls in cars to provide better handling/safety.

I would agree that the stability control uses additional sensors beyond the wheel rotation sensors. The Ford website was interesting and so was the youtube video. However, there was precious little details on how the system detects sway. From what I could gather, it would be likely that the system was detecting TM sway when TM was in a tight turn even though there was no sway. As the poster noted, the system probably applied the brakes thinking the TM was swaying even though it wasn't. As far as I am concerned, this is a design or adjustment failure of the system. I would not want to have the brakes applied when there was no need - it could be dangerous or at least unnerving for the driver.

As systems get more and more sophisticated, unwanted side effects are more likely to creep in - IMHO.

Thanks again for the information.

Take care,

Phil

[T and C]

First of all, let say a hearty thank you to those who weighed in to help me solve this puzzle. As most of you suspected, the problem seems to have been in the Traction Control System.

When I bought the truck I sat down and read through the Owner's Manual. Naturally, one already knows a lot of the stuff in there, and some of it can be very technical as well. Well, I got out the manual again and did some careful reading in the appropriate sections.

It seems that the Roll Stability Control, the TCS, the Electronic Stability Control and the Trailer Sway Control are all parts of one system. The TSC, it says, only activates at speeds over 40 mph, (64 kph).

On another page, it says that certain driving manuvers "may activate the ESC system". Among them I read, "cornering while towing a heavily loaded trailer".

So, the thing must have activated because I was: a. going more that 40 mph. b. making a tight corner towing a trailer. I guess it thinks 4000 lbs is "heavily loaded".

In addition, the manual give directions for turning off the system. There is one way to turn it off while travelling less than 35 mph which turns off the RSC, ESC, and TCS. There is another way to turn off only the TCS while going over 35 mph. Then a footnote below says, "TCS is enabled but with higher entry thresholds compared to full system".

Hmmm...so it is turned off but is still on. So it is still watching what is going on but won't intervene unless I REALLY screw up.

All I can say, besides thanks, is that its a good thing I am good at analyzing what I read. This makes me think of a friend who once bought a high end BMW. With the purchase they gave him a 4 hour class in how to understand and operate all the car's systems.

Tom