Serious Brake-Locking, Intermittent - HELP NEEDED

[Mrs__C_]

Below is a write-up my husband did concerning our brake problem:

Problem Statement

Intermittently, the brakes of our fifth wheel trailer lock up for less than one second, while being towed by our Chevy truck.

Incident Details

Over the last 2 years, we have experienced 6 incidents of the trailer brakes locking up, each for less than one second. Each incident is during “tow mode”, where we our truck is hitched to our fifth wheel. The following are observations during these incidents:

All incidents occurred during highway speed while pulling the trailer.
The truck and trailer experience brief lock-up of trailer brakes
We are in “tow mode”
A few of the incidents occurred while cruise control was active; most of the incidents did not have cruise control active.
The speed is reduced due trailer brake activation.
The incident takes less than one second.
The vehicle RPMs do not go up.
The truck brake light and ABS light both go on.
We always pull over to the shoulder after the incident.
Brake light and ABS light stay on until the engine is turned off, restarted, and vehicle brought to at least idling speed.

Our truck and trailer

Chevy Silverado 3500HD LTZ, crew cab, long-bed, dually truck. We have no performance enhancing computer chips or devices. Stock.

Redwood 38BR fifth wheel (41 feet)

What we have done so far

We have taken the Chevy truck to different dealers a total of four times. Each time the dealer checks the EBCM and determines any codes. Nothing has been found wrong the Chevy truck by any of the dealers. Codes have been documented.
For example, in the last incident, the EBCM threw a “U0100” code. According to obd-codes.com, “The generic OBD trouble code U0100 is a serious situation where the signals between the electronic control module (ECM) or the powertrain control module (PCM) and a particular module have been lost. There could also be a problem with the CAN bus wiring disrupting communications.”
We have had our trailer in for service a couple of times, with nothing found so far.
I have talked with the manufacturer of the trailer brake actuator (Cargo Towing Systems).
I have talked with the manufacturer of the trailer (Crossroads).
I have had many conversations with Chevy mechanics.
I have de-activated my truck air springs, to be sure that there are no current spikes being given to the EBCM due to this aftermarket device. The problem has re-occurred after the air springs were de-activated.
I have had my truck external fuel tank wiring checked by the Chevy dealer to be sure it is wired properly.
I have purchased a new CAM MOD device to support the trailer brake actuator, according to Cargo Towing Solutions.
I have replaced the 7-pin connector that goes between the truck and trailer, including the plug-in receptacle that mounts to the truck bed.
I am ready to have the trailer gone over top to bottom to see if there are any potential intermittent shorts (not an easy task).

Summary

I’m looking for ideas on what to do to solve this problem, before someone gets hurt.

[raross61]

If you want to send me a private message, I have another more complicated idea, we might chat about if you would be interested? Bob in Oregon Raining Today Grrr!

[raross61]

Is there any way you could hook up a car horn or some audio device to the brake wire temporary? Connected to the electro-magnet wire on the brake you know is locking? That way you could leave the truck running with the e-brake on and wheels chocked, then you could do what the old ford eecIV manusl used to have us do which I think they called a "wiggle test", moving all switches or wires you think might be the problem, when the horn honk's even for 1/4 second it was getting power and is probably where the problem is! Just a thought Bob in Heavy Equipment Tech Full Time

[Mrs__C_]

Thank you all very much! My husband (Carl) says these are really good suggestions. Thank you!

[mike-s]

Do the truck's brake and ABS lights ever come on when NOT towing? What brake controller - is it a built-in (not an add-on)?

Here's another vote for checking the breakaway switch. If it were to short, it would backfeed 12V into the truck's brake signal, which may cause the truck's brake controller to warn of a brake/ABS issue.

[YC_1]

Have you taken apart the umbilical cord connections as well as the truck socket?

I would also follow the wiring under the TT to see if any of the grounds are bad.

[Chuck_thehammer]

intermittent connection in the TRUCK.

main clue. brake light and ABS are ON till truck is turned off..

dozens of connector pins in the ABS system.. only take ONE to get loose/bad.. even for a second. or a bad ABS controller (intermittent)

if it was the Trailer.. it would affect the controller for the trailer.. and nothing to do with the ABS light/circuit.

but being such a seldom problem, maybe difficult to PROVE a part/wire/connector.

my opinion. retired auto mechanic.

[Mandalay_Parr]

I would start by checking the breakaway switch. Not sure about the lights on the truck.

[rhagfo]

Until I read the ABS and Brake light coming on in the TV, I was going to think something to do will possibly a bad break away switch. I don't know is supplying 12 volts to the brakes going to cause those lights to come on.