Is Emergency Brake Assist causing jerking

[Ken n Rita]

I have a 2014 Canyon Star towing a 2019 Ranger using a Stay-n-play braking system. Since installation, I have found whenever I brake hard, like stopping for a highway speed light, the whole rig is jerked during the last 1-2 seconds of braking. I even took a video of it which shows the pedal down normally until the last second before stopping when the pedal goes another inch down. This results in the toad stopping immediately and jerking against the MH. I think this might be the Emergency Brake Assist system which is supposed to increase brake pedal pressure during an emergency stop. If so, why on earth would it be active during factory correct flat tow mode? Any one else had this problem as I think the EBA is now common on most cars. Unfortunately I only have the clip in .mov or .avi format which will not upload.

[Skip426]

From your description , I'd be inclined to think this is happening at the toad's ABS cut out speed .
Above the speed the ABS function will prevent lock up, and keep the pedal stationary by maintaining brake fluid pressure , below you get lock up and the pedal drops as the ABS fluid pump stops cycling. .

I'd think that if the EBA was active in flat tow mode the extra braking would start at brake application due to the proximity of the coach .

I'd think you have a question for Ford Engineering , the fix maybe to pull the fuses on the ABS system for a test.

[Skip426]

OK; after reflecting on your issue a second thought .

Neither ABS or EBA should be active in flat tow mode .

If you're positive you've followed all the instructions to the letter ; for putting the truck into flat tow mode ; I'm thinking calling Ford is the next best step.

[Ken n Rita]

I got a link to the Ranger forum where this problem has been discussed. They think the ABS is still on. Here is the link https://www.ranger5g.com/forum/threa...ng-issue.4005/

[Skip426]

Thanks for the link , seems to confirm my initial thoughts on ABS still on , hope that Ford has done some upgrades to the " flat tow mode " over the three years since the issue was discussed .

[NXR]

Can you confirm whether this statement from the Stay-IN-Play DUO manual is correct for your installation?

The system should not come on in normal stopping below 20 mph.

If you are moving slow and hit the brakes do the DUO red LED lights come on or do you have another indicator inside the motorhome?

This may be a simple as you have the sensitivity too sensitive. If you think that may be the issue try moving the knob upwards 1/16" (which is really difficult to gauge for me).

I would not think Emergency Braking Assist or Antilock would be the problem at those low speeds. You're certainly not in a "brake pedal to the metal" situation to trigger EBA. I don't know how your ABS works but I'd still be surprised if it works below 5 MPH, especially if all wheels are turning at the same speed. ABS should decrease braking effort to avoid a skid, not increase it.

As an aside, you could set a phone inside and calling you while you test drive so you can hear any abnormal sounds in real time.

Ray

EBA video:

https://www.youtube.com/watch?v=BeAuJflJk7c

[Ken n Rita]

Yes that is true. The braking system comes on at speeds greater than 20. At speeds less than 20 it doe not come on. However, when stopping from over 20, like highway speeds, it comes on just fine but is jolted during the last 1 second of stopping. I have videoed this from inside the toad and can confirm the pedal comes down as normal until about the last 1 sec then the pedal comes down quickly another inch which causes the jolt. I can lessen the sensitivity and the jolt occurs less, but it also makes my toad brakes less helpful. i want them to assist in normal braking not just to be used in emergency situations. I am now going to disable toad's abs system and see if that stops the jerk. If it does then that is likely what is going on.

[Ken n Rita]

Hi, I have a video clip (about 5 sec) that shows this well. How to I post that?

[NXR]

Originally Posted by Ken n Rita

Hi, I have a video clip (about 5 sec) that shows this well. How to I post that?

I don't think you can directly. I've created a new folder on Microsoft OneDrive, put the video in it, and then set the folder to be shared to everyone with Edit permissions turned off (it's on by default).

When you share the folder you can get a link. Just paste the link into a post here.

Ray

[Ken n Rita]

I put a small clip into dropbox. You can see and hear the clunk and jerk of the brake pedal down in the last second of stopping. In the next few days, I will try to disable the ABS system and see if it goes away. Here is the link https://www.dropbox.com/s/og42ucniz7...0clip.mp4?dl=0

[NXR]

Yeah, that's interesting.

Normally the ABS releases the brakes so the question is what is causing the brakes to apply harder. Have you contacted Demco? If not I would. I found their support to be better than superb when I had a baseplate installation problem.

Ray

[Ken n Rita]

Thanks for your thoughts here. Yes I have been in close contact with Demco. I first showed the video to them. They are unable to think how their unit could act like this. I am posting a screenshot of a slow motion analysis that I did. It shows a 1 sec slice after the Demco unit has lowered the pedal normally and just as the pedal is jerked downward. I can hear the Demco pump running in the background audio. At 53 sec, I hear a sound like a whump from the truck. At 53.5 sec, the pedal starts it's jerk down. At 54 sec, I head the Demco pump turn off. ( This is right as the truck is stopped and the inertia switch should shut it down). At 54+ sec. the pedal start back up. The lower panel shows the audio track. The real test of ABS question is to pull the fuse and try stopping. I will do this in a day or two. I also am aware of some kind of Emergency Barking system that pressed the pedal harder in an emergency stop. I don't know how to disable that so far. Thanks to you all for staying with me on the troubleshoot. I know we can solve it eventually.

[Ken n Rita]

I think I have had a breakthrough. I read about the feature call Emergency Brake Assist. It is a part of the Electronic Stability Control system. It is supposed to apply the brakes hard if it senses that the driver is in an "emergency stop situation. This seems a lot like what has been happening to me. However, it has no place being on the a flat tow situation. I learned that if you press the button to turn on the stability, it just turns off the traction control portion. You have to press and hold the button for 3-4sec. until the Stability Control system turns off. This must be done while the car is running. The immediately go to flat tow mode. If the car is started again it will come back on automatically. I tried a test towing the ranger with it engaged and the jerk was there. I disabled the system as described above, tested again and no jerk. Just a nice even stop. My next step is to talk to Ford dealer or Ford engineering about the logic of it remaining on during flat tow. Anyone know a number for Ford Engineering? Also let me say a BIG THANK YOU to all who helped me with the problem. You are the greatest !!

[NXR]

Nice find. Which EXACT 2019 Ford Ranger do you have? On the NHTSA's site I see four:

PU/CC 4WD
PU/CC 2WD
PU/EC 4x4
PU/EC 4x2

I'm guessing the "P" means "Pickup and "EC" means "Extended Cab".

For the PU/CC and 4WD the NHTSA shows 77 Manufacturer Communications here:

https://www.nhtsa.gov/vehicle/2019/F...Communications

Click the + sign to read the description.

Click on any Associated Document to see the actual PDFs from Ford.

At a glance I did not see anything applicable, though.

Have you ever had any firmware updates done at the dealership? There's a small chance you may be fighting a battle that was already won, so to speak.

The description in the Owners Manual of AEB is interesting:

Emergency Brake Assist
Emergency brake assist detects when you brake heavily by measuring the rate at which you press the brake pedal. It provides maximum braking efficiency as long as you press the pedal. Emergency brake assist can reduce stopping distances in critical situations.

From what you've found, it may be that AEB is detecting the rate that the Stay-IN-Play DUO moves the pedal and also how long it keeps it depressed.

Again, great work.

Ray