integrated brakes "trailer not connected"

[leshetaz]

We have a 2013 XLR 40 foot toy hauler (3 axles) and a 2015 3500 DENALI HD with integrated brakes. The truck shows an error: "trailer not connected" . We are looking for a workaround. We have consulted with GMC (turned in a complaint) and they will not fix the problem. The dealer tried other trucks - The 2014 did not show the error but all 2015 showed the same error. The third axle is outside their safety parameters according to the engineers at GMC. The truck shows this error repeatedly while traveling. They told us there is not a fix and they close our official complaint.

[mooseman411]

Pretty much same issue I am having. I did find a TSB for the 1500's that were having the same problems but gm states we are not aware of it. Ha!

[leshetaz]

Our dealer found a TSB for our truck and we talked to the engineers at GM. The engineers said that the change was made for safety. I put in a formal complain and they entertained it a couple of weeks. They called me and said they were not going to fix this problem, being that it would cause a safety issue. They also told us that our truck was not designed to pull a three axle trailer. We exploded. Take the truck back. The dealer tried to find us a replacement. All the trucks (2015 3500 dully) did the same thing. I m hoping there is someone out there that can give us a work around. Otherwise we are going to replace the integrated trailer brakes. On a long trip this is very annoying.

[fjtort2]

Mine just started doing this after 26,000 miles. Is there a fix?

[fjtort2]

Anybody?

[Gecko50]

So let me get this correct. I own a 2016 GMC Diesel Denali 3500 4 x 4 and it comes with a substantial weight towing abilities that GM totes as one of the highest in the class of trucks. Now mind you this is NOT a 1500 (Not beating you lightweight trucks owners). So when I hook up my 18K rated trailer with 3 axles as it is required by law and or safety to stop the trailer GM decides its out of their parameters! (Well before 2014 it was ok) How can a company sell a truck and say they didn't take into consideration of 3 axles! You check any aftermarket trailer brake controllers! I'm sure the resistance or voltage needed is increased by each brake assembly but COME ON! This is a reminder and cop out like the design of the "WIRELESS CHARGING PAD" This is too easy and some one higher up should FIRE the dam engineers and their design team. The entire bunch including the lead engineer. THAT person should be put out the front door with a cardboard box and in their file "NOT ELIGIBLE FOR REHIRE"! They screw up and NOW want a easy out! I wonder IF really higher up in major management knows this crap. Some what like the who ignition fiasco. They wonder why they loose customers, why they get lawsuits "If you want you can go out and purchase a add on brake controller" AFTER giving US (GM) thousands of your hard earned cash for you truck! There should be in the typical generic owners manual (It looks to cover every vehicle GM makes with all "disclaimers if it applies to your vehicle" We haven't consider that this vehicle and the design "MAY NOT WORK AS ADVERTISED" SO PLEASE PROVIDE AMPLE RESERVE CASH TO PURCHASE ADDITIONAL ITEMS FOR OUR LACK OF OUR DESIGN / ENGINEERING TEAM ABILITIES / FAILURES to give you what is advertised and INSTALLED on the truck you just purchased. By the way IF you install these items they WILL cause the warranty void with no recourse. What a SCAM. I hope this does NOT occur on my NEW truck with less than 1,000 miles on it. I towed it with my 1999 Chevrolet C3500 gasser with a aftermarket brake controller. Got a New 2014 GMC C 3500 Denali diesel C3500 and traded it in with less than 16K miles for this new 2016 Denali. All pulling my 48 foot goose neck trailer. I will NOT be a happy customer if this happens on my truck.

 

I WISH they would provide a complete listing of design engineers with the lead engineer names for each section of the vehicles GM designs and who provides the approval process. I think IF their names are listed they may change their thought process. Put the pride back in and claim responsibilities. Who over rode whom! This is so we owner can ask them what rock they lived under during design. Forget about the refi 8 years ago! It should be no longer a excuse. Claim responsibilities and move on.

 

Chuck

PAE

[Gecko50]

Well for the rant above. Now I hope its behind me. I hope this does NOT occur on my truck. I am very picky on my vehicles, when my wife met me I was cleaning my daily driver air vents with a tooth brush! I don't do that anymore.... I had a 7 pin trailer plug added to my truck in the bed for my 48 foot trailer, I insisted that a complete new 7 pin harness with factory plug adapters be used with no splices, kinda like a tee harness. It intercepts the truck harness at the rear of the truck bed. My truck did come with the camper wires tie wrapped in the rear under the bed. I am one that if you splice and with the weather elements splices will go bad. The conditions will be at its worse. A pre-made harness should reduce any type of poor splice conditions.

Just a thought with all the computer controlled things on our trucks that it may see high resistance splices and create the above problems. Just thinking out loud. Has the OP tried a different 3 axle trailer? Why does it take so long for the truck to post the failed conditions? Is it with poor connections it would increase a failure condition, Just sayn???

 

Chuck

PAE

[fjtort2]

Finally applied dielectric grease to both male and female it so far it has solved the problem! Knock on wood!

[newdude]

Have your trailers checked. GM has been seeing a lot of this and things are getting replaced due to issues with the customer's trailers and not an issue with the truck, or the modules itself. The best trailer side connectors to have are Pollak as that is who supplies most of the OEM's and their truck side connectors. Pollak to Pollak ensures the best connection.

 

#PIT5509: Diagnostic Tip - Integrated Trailer Brake Control System - (Jun 14, 2016)

 

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern

Some customers may comment that when they have a trailer connected to the vehicle, they get a "Check Trailer Wiring" or "Service Trailer Brake System” message on the DIC. DTC C1114 could be set in the Chassis Control Module (CCM).

Diagnosing these concerns can be difficult because the issue could either be related to the truck or the trailer. This PI is to provide some additional diagnostic information for these three symptoms:

• Check Trailer Wiring message
• Check Trailer Wiring message with DTC C1114
• Service Trailer Brake System message with DTC C1114

Recommendation/Instructions General Information

The trailer brake control system on the new body style trucks is compatible with two types of trailer brake systems: electromagnetic or electro-over hydraulic trailer brakes. The Chassis Control Module K38 (CCM) must determine which type of brakes the trailer is equipped with so the system can output correctly for the trailer's brake system. Because the CCM has to determine the type of trailer brake system that is being used, it can be sensitive to a variety of trailer wiring issues.

The Trailer Brake Power Control Module K133 continuously sends a test pulse out on the trailer control circuit 47, looking for a trailer that has been connected, and also to monitor for circuit faults. The way the test pulse reacts when a trailer is connected is how the CCM determines which type of braking system the trailer is equipped with.

 

Even after the system detects the trailer, it will continue to send this test pulse on circuit 47, which now is monitoring both the truck and trailer circuitry. Circuit 47 continues to be monitored for any faults so the driver can be notified of any issues that may occur within the truck or trailer, as well as, to determine when the trailer is disconnected from the truck. If the CCM detects an issue, it will either display a "Check Trailer Wiring" or "Service Trailer Brake System" message on the DIC. See DIC message/DIC below.

 

Electro-over Hydraulic Trailer Brakes

Electro-over hydraulic brake systems have some unique characteristics and here are a couple examples:

• The electro-over hydraulic brake pump motor needs a minimum duty cycle of approximately 20-30% to turn on the pump motor. If the user gain is set too low, or during light brake pedal apply the pump motor may not turn on. This is normal. Increasing the user gain or brake pedal pressure will help alleviate this concern.
• When applying the brake pedal at 0 mph (stopped) there will be no output from the truck's trailer brake system to the electro-over hydraulic pump motor. This is normal.

Testing The Truck's Trailer Brake System

In many cases, trailer brake issues are the result of trailer wiring concerns and they are not related to the actual vehicle's wiring. Most trailers with these wiring issues do not have high standards in relation to wiring/connections/splices/routing practices (see examples in Step 3 below) when compared to similar automotive practices for wiring/connections/splices/routing. Because of this, the CCM can set faults, which can be hard to determine if they are related to the truck or trailer.

 

The easiest and fastest way to test the truck is to make a tester using trailer brake magnets. This type of tester utilizes actual trailer brake magnets and will load the truck's electrical system, just like a trailer would do without having to have the complete trailer. Shown below is an examples of such a tester. The trailer brake system will operate with 1 to 4 pairs of trailer brake magnets (1 pair of magnets = 1 axle). It is suggested to make a tester where the pairs of magnets can be added or removed to equal the same number of brakes as the customer's trailer.

 

Also, it is advised to make the harness long enough so it can be plugged into the truck's 7 way connector and have the magnets placed into the bed of the truck. When the tester is connected to the truck, the DIC will display "Trailer Connected" and GDS2 will show "Electro-magnetic" brakes in the CCM data parameter "Trailer Brake Type", refer to item 1 in "GDS2 Data" section below. If so, the vehicle can be driven to see if any fault messages or DTC's set. If none occur with the tester installed, the truck is operating correctly and the focus should be on the trailer wiring or 7 way connector.

 

DIC Message/ DTC's

It is important to understand and determine what message is being displayed, as well as, if DTC C1114 is setting. This will help determine what type of fault to inspect for on the trailer. Below is the combinations of message(s)/DTC to determine the type of fault the customer is experiencing:

• Check Trailer Wiring message with no DTC. This symptom is caused after the system detects a trailer and an open and/or high resistance occurs in circuit 47/trailer brake output circuit, during the same ignition cycle. NOTE: It is normal for the DIC to display "Check Trailer Wiring" when the trailer is disconnected from the truck while the ignition is in the run position.
• Check Trailer Wiring message with DTC C1114 (NO Service Trailer Brake message). This symptom is caused by a short to ground on circuit 47.
• Service Trailer Brake System with DTC C1114. This symptom is caused by a short to power on circuit 47 or a poor trailer ground

Trailer Issues

1. The most likely reason for many of these issues is a poor/loose connection between the truck and trailer 7-way connector. It is recommended to use a "Pollak HD" RV trailer connector, as shown in the latest version of PIT5311. Pollak is the OEM manufacturer of the truck's 7-way connector. By using a Pollak trailer connector, this will provide the best connection possible.
2. Shown below is an example of a 5th wheel trailer where the trailer harness has been routed over the top of the tailgate and plugged into the truck's bumper connector. While driving down the road, the trailer's wiring harness will bounce up and down (A), causing the trailer's 7-way connector to lose connection (B) with the truck. The fix in this case was to add the 5th wheel/camper wiring harness and route the 7-way connector's harness inside the box of the truck, as shown ©.

3. Note: This same concern can also happen with bumper pull trailers if there is an excessive length of harness. Securing the excessive trailer harness and installing the Pollak HD RV trailer connector per PIT5311 will help.

Poor trailer wiring connections, as shown below. General Motors does not recommend these type of connections, but many trailers utilize these connections. These type of connections are not robust and are not recommended, especially for brake wiring. Aftermarket trailer sway control devices, like the example shown below. These devices can apply the trailer's brakes to control trailer sway. When this happens, the truck will detect this and set DTC C1114. It will also display a "Service Trailer Brake" message on the DIC. NOTE: If a trailer sways this is likely caused by improper loading of the trailer, refer to the owner’s manual for more information The CCM is detecting the wrong type of trailer brakes. This is normally caused by an aftermarket device wired into the trailer. The example shown below is an electric over hydraulic-to-electric brake adapter. These adapters are used to make a truck that only works with electric trailer brakes work with a trailer that has electric over hydraulic brakes. These adapters are NOT recommended. In addition, the new body style trucks are compatible with both types of trailer brake systems: electro-magnetic or electro-over hydraulic.

 

[Daryl Z71]

Also make sure the connections for the plug are clean and free of debris. Wouldn't hurt to add dielectric grease either.

[jj46]

So some of you mention dielectric grease or other connection/trailer issues. That is all well and good, but the OP said that he was told "the truck is not designed to pull a 3 axle trailer". That is a pretty big statement. My neighbor pulls his 3 axle toy hauler with his F-350 and doesn't have any problems... so I'm curious as to the real issue here. Is it a 3 axle problem, or a connection/wiring/trailer problem?

[jhplak325]

Buddy of mine has a 2016 GMC Sierra dually and pulls a tri axle 5th wheel toy hauler without any issues with the factory brake controller.

[newdude]

So some of you mention dielectric grease or other connection/trailer issues. That is all well and good, but the OP said that he was told "the truck is not designed to pull a 3 axle trailer". That is a pretty big statement. My neighbor pulls his 3 axle toy hauler with his F-350 and doesn't have any problems... so I'm curious as to the real issue here. Is it a 3 axle problem, or a connection/wiring/trailer problem?

 

 

OP has either a truck or trailer issue. On 2015+up HD trucks, the trailer brake system is designed to handle a 1 to 4 axle trailer with trailer brakes. It is not a system design fault (aka. it can only handle a 2 axle trailer with brakes).

 

Also, a quote from the OP:

 

The third axle is outside their safety parameters according to the engineers at GMC.

 

 

If the trailer's third axle is out of some spec for the trailer brake system to properly control it, it sounds like that his problem lies within the trailer itself, rather than the truck, be it an electrical fault with that axle, or what have you.

 

Now...have we had customers come in with "Service Trailer Brake" before? Yep. The only part we replace that is common, is the dashboard integrated switch. We have yet to change a Trailer Brake Control Module, Chassis Control Module, or any other module related part with the ITBC system. And one guy had an issue with the receptacle on the bumper itself.

 

Some light reading below on the GM ITBC system for K2 HD trucks:

 

General Information

 

The trailer brake control system on the new body style trucks is compatible with two types of trailer brake systems: electromagnetic or electro-over hydraulic trailer brakes. The Chassis Control Module K38 (CCM) must determine which type of brakes the trailer is equipped with so the system can output correctly for the trailer's brake system. Because the CCM has to determine the type of trailer brake system that is being used, it can be sensitive to a variety of trailer wiring issues.

 

The Trailer Brake Control System is compatible with two types of Trailer Brake Systems as listed below:

1. Electric Brakes A controlled electrical output signal energizes an electric-magnet/lever arm assembly that directly actuates the brake mechanism. The GDS name for this system is “Electromagnetic Brakes”.
2. Electric Over Hydraulic Brakes A controlled electrical output signal energizes a remote, trailer mounted hydraulic pump to build brake pressure in a closed hydraulic system on the trailer. The hydraulic fluid pressure actuates the brake mechanism. The GDS name for this system is “Electrohydraulic Brakes”.

Trailer Brake Output Versus Trailer Brake Type

• The trailer brake system characterizes the trailer brakes as either Electric Brake or Electric Over Hydraulic Brake automatically. This characterization may be affected by the number, type, and age of the trailer brake magnets, as well as any other devices installed on the trailer brakes (i.e. adapters for Electric Over Hydraulic brake functionality).
• The trailer brake system is fully operational with either characterization.
• Some features of the trailer brake system may be different based on the trailer brake type characterization. An example of this is at zero speed, where pressing the service brake pedal will produce output when the trailer brakes are characterized as Electric Brakes, but not when characterized as Electric Over Hydraulic Brakes.
• Sliding the manual trailer brake apply lever will produce output at zero speed for either characterization.

The user gain allows the driver to adjust the amount of trailer brake output to match the trailer load and road surface. The controller determines the desired trailer brake output and provides a control signal to the K133 Trailer Brake Power Control Module. The K133 Trailer Brake Power Control Module amplifies the signal and provides the output required to activate the Electric or Electric Over Hydraulic trailer brakes.

The trailer brake control can support up to a maximum of four axles with electric trailer brakes (8 brake magnets).

 

 

[Tjeli]

^^ This ^^

 

I can almost gaurantee that the OP has a problem with their trailer that an older technology brake control is not picking up. The only problems we have seen with the ITBCs have been with electric over hydraulic brakes. (and there is a workaround for that)

 

-Eli

[rocnrol]

So.... my 2 cents on this. I have two trailers that I pull with my '15 2500, our '14 35' travel trailer and our 13 year old 18' car hauler. With the TT, zero issues, system works flawlessly. The car deck has had wiring issues since day one and has known issues with the brake wiring. I'll routinely get the aforementioned messages with that trailer hooked up.

 

 

 

Sent from my Z30 using Tapatalk