Electric Trailer Brake Question

Sounds like a class action lawsuit coming in the future... Hopefully this gets fixed before someone gets killed or even injured.

Keep us posted on the status. Thanks for the work to explain what is happening.

My advice would be give it up and do what Dave says and just use a separate controller. I have found that unless the problem is completely obvious, you will most always get the same answer from the dealer. "Operating as designed."

Is this problem only with the 2015 Rams or are previous years also affected?

I really appreciate the information you've provided. It blows my mind that the Chrysler engineers are having any difficulty at all in understanding the problem here as it's a really basic circuit. I think the big issue is how they came to the conclusion that an arbitrary duty cycle of 60 to 70 percent is mind blowing. If they can't figure out how this will affect the overall current flow through the brake solenoids they shouldn't be employed.

As for the dealers, I've found they don't have mechanics that understand theory, or can troubleshoot anymore. They rely heavily on test equipment, onboard computers, and factory troubleshooting tree's. The days when we invested in training and educating folks as to how it works so they could solve the tougher problems seem to have passed.

Boshog, Let me know if you need any data collected from a second source. I've got a portable scope, albeit a somewhat cheap one. I also have a clamp on DC ammeter etc. and a lot of experience in the troubleshooting and repair of simple control circuits like this, albeit from an aviation rather than automotive background.

I already filed a complaint with the NHTSB and they responded with a request for more information. So I wrote a paper with my findings and provided the paper to them.

I have the same axles as searching_ut, Dexter 7,200 pound X 2. Using a Fluke DC clamp meter I measured 12.6 amps in to the fivers brakes using my 2013 RAM with the ITBM. All my testes were done with the engine running. I needed to prove it wasn't my trailer even after having the dealer test them three times. It isn't your trailer axles that are not working.

I had my RV dealer document the fiver's brake test because the Chrysler dealer was blaming the trailer wiring.


Here is what the dealer's work order stated;


For those with tech knowledge it is amazing a Chrysler dealership would publish something as outrageous as this. For those not quit up on how this works it is rather simple. The pulse width (PWM) supplied to the trailer has an off time and an on time. The more trailer braking action required the more on time the PWM signal has. This provides an increasing equivalent voltage to the trailer brakes. You just can't take a motor and say because in spins the ITBM works.

I did talk to the dealership service folks but any conversation about voltage levels and PWM signal went right over their head. The DC motor test came from Chrysler's STAR tech support lines available to the dealers. This is really sad and says a lot about Chrysler engineering.

boshog, I think you are light yers beyond any dodge service center and certainly tht includes me.

In my opinion you have ample data to initiate a case/report/complaint (whatever they call it) with the NHTSB.

In the meantime this dumb ole country boy would strap on something like a good prodigy just to take care of my own butt.

What a bummer.

God luck.

Wow, I've got to say Boshog, you've done your homework. I will say that based on my experience to date, the brakes don't work over 30mph either as the incident that got my attention happened to when I tried to do a panic stop at approximately 50mph and had virtually no trailer brakes. Although and emergency stop, I should have had room to bring it to a stop in the distance I had available. As it was I had to maneuver around an idiot who had slid through a stop sign, which isn't at all fun with 14k or so behind a truck that doesn't handle particularly well empty. It's set up for hauling not handling.

As to the questions of brake current draw, the dealer used a tester at the trailer connector that applies 12vdc to the brake circuit while measuring current flow. According to dexter, the coils on these brakes should draw approximately 3amps each. If you have wiring issues, an open coil or whatnot the current draw will be less. As part of the discussion I had with a dexter rep they also indicated that the brakes aren't designed to lock up with a loaded trailer. Given that Ram has evidently chosen to reduce the braking even further we now have a situation that is seriously unsafe.

For the record, the 5er has been towed behind a ford with a factory controller and the brakes worked great. Doing this was a pain since I had to pull the Anderson hitch adapter off first.

Unfortunately, I've only had the 5er a couple months and the truck approximately 3 so I'm just getting the feel for things, and when it wasn't right initially I didn't suspect serious design flaws so I just started looking into the issue through the dealers. I don't have room to store the 5er at the house, and getting at it now with all the snow is difficult. Took me almost 30 minutes to park it last night when returning from the dealer because I couldn't get traction in the 7 or 8 inches of snow in the storage lot. Almost had to resort to chains.

Now that I have some background I'll insist the truck dealer contacts Chrysler if things "check out". I'll wait to see what they're going to do to fix the problem prior to figuring out what the next course of action should be.

Finally, if and when I try and do further testing, my initial thoughts are that all I will have to is figure out how to put an ammeter/data logger in the circuit to measure total current flow, while at the same time capturing the pulse width/voltage on a scope. I'm not sure what that would prove though as it appears from reading everything Boshog has done so far there isn't much else to learn. It appears to be a serious design flaw from the factory, with the only thing left resolved is what they're going to do about it before someone gets killed.

GREAT info!!!! Love it

Still not sold on PWM for inductive actuators on a self wedging drum/shoe
setup. Why ABS doesn't work well for vehicles with drum/shoe setups.
Where to put the tone ring (gear ring) and most put it on the drive
shaft. That self wedging shoes do NOT release quickly or fast enough
for ABS cycling. They could increase the release spring tension, but
then the two curves would be going in the wrong directions...it would
still help and better than no PWM

It would be good to see the output as you have captured vs the actual
at the trailer magnet, but almost impossible to do easily

The P2/P3 are inertia based, so the only association with the TV brake
pedal is as the initiator. Factored by the boost setting.

Once it senses deceleration, it will continue to increase braking until
either the TV brake pedal switch is deactivated or deceleration drops
below some preset or stops

I readjust the trailer brakes throughout the trip, as they need to be
very tight for my style of driving

Why asked if the ITBM has both MC PSI sense and TV brake pedal switch
sense.

The P2/P3 will lead the TV braking if the pedal switch is setup well.
I can stop the whole thing just by touching the pedal and NOT go far
enough to develop MC PSI, which is what MC PSI sensed can NOT do without
that pedal switch sense

From this base line info, my guess is that the whole issue at hand is
with the software algorithms. Also why asking if the ITBM also has
an accelerometer. Without one, the software will go to look up tables
for MC PSI vs output of the ITBM to the plug

Curious why they reduced the output for the higher class truck vs the
lower class truck. The P2/P3 is NOT dependent on MC PSI...just decel
rate. Assumption is that your chart is interpolated to pedal/MC PSI
for the Prodigy and seems the engineers used those metrics for their
look up table. If they looked at my setup, where there is no MC PSI...what
would they have done?

Another potential issue is voltage drop at the magnets. Again need to
know where you measured the trailer brake current draw. At the TV plug
or at the trailer brake wires leading into the backing plate.

Also, all of those algorithms go out the window if the TV has performance
braking upgrades/mods...

Searching_Ut wrote:
Has the OP been able to resolve his braking issue yet?

I ask because I have pretty much the same setup, same issue. 2015 Ram 3500 with bighorn 5er, dexter 7k axles with 12x2 inch neveradjust brakes. Just drug the 5er back from the dealer where they did a good checkout on the brakes, 12.3 amp current draw, pulled two drums checked for contamination etc. and they looked good. When I came to pick it up they came out and we agreed the brakes weren't working good on my rig. Ran a cord out the window, went up to 20mph and pulled the breakaway cable and brakes worked real good. Just can't get anything like that sort of braking in normal operation with the 5er really pushing the truck hard during braking.

The truck is scheduled with the dealer for Monday. I'm getting an intermittent brake light inop signal indication on the EVIC when using the truck as my commuter for the snowstorms we've been having, and twice I've got a message to service the air suspension. They both clear themselves.

The checks I've made are brake signal voltage, which only measured 7.4 volts to the brakes when I tested with a voltmeter, truck set to heavy electric, gain maxed at 10. I'm going to make up a harness to hook to the bumper pull plug while my 5er is connected to the bed connector and run the wire through the back window into the cab so I can hook up a scope and see what sort of duty cycle I'm getting pulse wise out of the brake controller while actually in use. (it needs a trailer connected to work) The pulse duration must be pretty low for my multimeter to be only averaging it out to 7.4 volts, but I'll be able to know for sure when I measure it.

It would be interesting to know if others with a similar setup are having issues.

No, the issue isn't resolved but Chrysler may not think it is an issue since the problem is the result of their intentional design, as strange as this may sound.

The integrated brake controller on 2015/16 RAMs (all models) are designed to put out about 70% braking effort when the vehicle is traveling less than 30 MPH regardless of the amount of braking effort the tow vehicle applies. I am not able to get more than 72% over 30 MPH on my truck (see graph below). It gets worse, the manual slider does not over-ride the 70% rule meaning you can not properly set the gain value.

It gets even worst. The actual output from the ITBM is not proportional, that is, the harder the tow vehicle brakes, the less amount of braking signal is sent to the trailer brakes as illustrated in the following graph. You can see the difference in behavior between the 2013 and the 2015 ITBM.



There is an on-going discussion about this here http://www.ramforum.com/f119/brake_controller-71708/

Fast Lane Trucks is looking in to the issue and I am in contact with a quality engineer at Chrysler whom has visited me and my truck to see the issue first hand (I live about 10 miles away from Chrysler's headquarters). Obviously this wasn't very well though through by Chrysler, just be glad you do not have electric over hydraulic brakes.

Prodigy offers a cable that goes to their aftermarket controllers and plugs directly in to the cable that plugs in to the ITBM, part number 3021-P, (good marketing on their part) and I am using a P2 until Chrysler can get it together but this will likely take years.

You can build a trailer brake simulator out of an inductor and a load resistor, I used the armature of a windshield wiper motor as the inductor and a five watt 6 ohm resistor as the load. You could also pick up an electromagnet from your local trailer supply store.

Here is one of many scope shots I captured during my root cause of the problem.


This issue is not documented and dealers do not have a clue how to troubleshoot the brake output from the ITBM.

Just to clarify the issue, at 70%, many trailers will stop as expected, but the bigger 12 inch brakes on big fivers, they need more than 7 volts to do the job. Because of this, not everyone towing will see the issue.

Moderator edit to re-size pictures to forum recommended limit of 640px maximum width.

Am assuming Integrated Trailer Brake Controller, right ?

Assuming this has a MC Fluid PSI sensor, right ?

Ask if this system senses TV brake pedal brake light switch in addition
to the MC PSI sensor ?

How tight were the trailer shoes adjusted ? or is this a disc setup ?
12 x 2 says to me, drum/shoe setup

Was the 12.3 amp draw from each brake coil, or total for the trailer ?
Where was that measured ? At each brake coil/magnet or at the trailer
plug ? {edit}...most trailer drum/shoe brake coil spec's I've seen list
them from 2.5/each, 3/each to 4/each

What does the gain or boost setting adjust? The signal from the MC sensor
and/or the brake pedal switch ?

Pulling the trailer break-a-way pin depends on where the trailer battery is
connected to the trailer brake harness. If it is at the trailer plug or is
it tied closer to the trailer axle/brakes ?

Where was the TV brake signal voltage measured ? It should have been measured
at the TV plug and at full load (whatever the trailer brake coil/magnets add
up to be

"Pulse duration"...meaning that this ITBM has a PWM output? Wonder about the
inductive hysteresis of the trailer brake coils. Must be some pretty fast
coils, otherwise it will look like a wavy input power source...or the PWM
signal does not cycle fast

Suggest also testing with a hot wire to the trailer brakes from your TV battery
and a switch or push-button to turn them on/off while driving

Since one of these highly integrated brake controllers...note that it is controlled
by the ECU or one of the master computers on-board.

Suggest getting a flow diagram and/or truth table for it and note that the
computer is also tied into ABS, traction control, sway control (if you have
it) and a host of other sub-systems on board.

Much more, but the first thing I'd check is the system ground, the TV to trailer
ground and any sub-feeds. Since you have an oscilloscope, check for noise against
the computer(s) specifications for noise

Any aftermarket electronics? Even Bluetooth stuff. Both on the trailer and
the TV

Can you tow another trailer with your TV to check how it works there?
And have your trailer towed by another TV. Divide and conquer...