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Integrated brake controller


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I have an 08 3500HD with the ITBC.

 

Thing is flaky.

 

Sometimes, with no trailer attached, I get a DIC warning "Service Trailer Brake System".

 

Many times, when hooking up my trailer it fails to recognize that the trailer is there.

 

Other times it will work fine until I stop the engine for fuel stop, etc., Then it will not see the trailer when I restart. If I stop the engine, then unhook and rehook the trailer it will again recognize the trailer when I restart.

 

I have pulled all the connectors and checked for corrosion, bent pins, whatever. Everything seems fine. Trailer brake resistance check is good, and all wires are secure.

 

 

 

 

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I have a 5th wheel that I towed with my old 2003 1500 Sierra and now with my 2012 2500 Sierra. Once in while with my old truck the controller would see a short in the system but the brakes still worked ok. When I moved over to the new truck and every thing seem just hunky-dory until one day the factory brake controller saw a short. That is when I started checking the trailer wiring. I found a worn spot on the bottom of the 7 conductor cable just as it passed through the trailer frame. It went all the way through the outside rubber insulation and the conductor insulation just barely. It was enough to cause the short to show up in the controllers. So I would plug you trailer into someone else's truck and see if you have the same trouble. If yes, start checking the trailer wiring. If no problem, start checking your truck wiring. Check where wires move or rub. Good Luck! Electrical issues are a pain to find sometimes. Yours issue may be a corroded connection in the connector or a broken lead. If you haven't pulled it apart, that is where I would go next.

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Getting an ITBC system to work correctly can be a frustrating problem with many causes and solutions. Finding exactly what is causing your problem may take some time and a lot of searching. I had a similar problem and finally fixed it, though I'm not sure exactly what specifically I did that fixed the problem as I did several things at one time.

 

Here is one place to start and information copied from other sources.

 

.

TECHNICAL

Bulletin No.: 09-05-22-004

Date: November 05, 2009

Subject: No "Trailer Connected" Message on Driver Information Center (DIC) at Startup When Trailer is Connected (Reprogram ITBCM)

Models:
2007-2008 Chevrolet Silverado
2007-2008 GMC Sierra
Equipped with Integrated Trailer Brake (RPO JL1)

Condition

Some customers may comment that when they connect their trailer, with the engine off, and after they start the engine, the Trailer Connected message is not displayed on the DIC. With the engine running, if the trailer connector is cycled, the vehicle will detect the trailer and display Trailer Connected. This concern should only affect trailers equipped with trailer brakes on a single axle.

Cause

The trailer brake control system is only compatible with trailers equipped with electric trailer brakes. The system will not work or detect trailers equipped with any other types of brakes such as surge, air or electric-over-hydraulic trailer brake systems. When a trailer is connected, the Trailer Brake Control Module (TBCM) performs a test to determine if the trailer is equipped with electric trailer brakes. If the trailer wiring or electric trailer brake magnets have additional resistance (caused by poor connections, corrosion, improper splices, etc.), the TBCM may not be able to detect the trailer.

Correction

A revised calibration has been developed to address these issues. Reprogram the Integrated Trailer Brake Control Module (ITBCM) with updated calibration files using the TIS2WEB Service Programming System (SPS) application. Refer to SI and Service Programming System (SPS) documentation for programming instructions, if required. Refer to Trailer Brake Control Module Programming and Setup in SI.

 

AND

 

Service Trailer
Brake Message
Some owners of a 2007-08 Silverado or
Sierra with RPO JL1 may comment of a
Service Trailer Brake System message dis-
played on the DIC. DTCs C1112 and/or C1114
will be set in the Trailer Brake Control Module
(TBCM).
TIP:
This concern may occur with or without
a trailer connected to the vehicle.
Updated TBCM calibrations have been
released in TIS2Web to improve TBCM diag -
nostics for a high resistance short to voltage
concern. The Tech 2 can be used to monitor the
TBCM Relay Feedback Signal parameter
located under Chassis/Trailer Brake Control
Module/Data Display to help determine if there
is a short to voltage.
The normal voltage reading is between
3.2–4.1 volts. If the voltage is higher, the
updated calibration will help. If the voltage is
lower, the updated calibration should still be
installed. However, additional diagnostics may
be needed to correct the concern.
TIP:
Refer to the latest version of
PIT4595D and appropriate SI diagnostics for
additional help.

 

AND

 

Trailer Brake Control System Description Summary
There are 3 main components to the Integrated Trailer Brake Control System (i.e. The Trailer Brake
Control Switch (TBCS), the Trailer Brake Control Module (TBCM ), and the Trailer Brake Control Relay
(TBCR).)
There are three other primary inputs to the TBCM. Two come via the Serial Data Network. One is
directly wired to the TBCM. The inputs coming via the Serial Data Network are the Wheel speed data
and the Master Cylinder Pressure Sensor’s pressure data. The Master Cylinder Sensor input is indirectly
used by the TBCM to scale the trailer braking in relationship to the pressure placed on the foot pedal.
The wheel speed data is indirectly used to validate the brake signal and validate related errors. The Stop
Lamp Switch is directly wired directly the TBCM and used for a calculation to double check whether you
are really pressing the brake pedal, among other things.
Also, with a data communications network involved, the Engine Control Unit is also involved as it is
managing the communications of the network. There are several codes that can be generated by the
ECU and the TBCM. (This is why it is best to start ITBC troubleshooting by reading the vehicle’s codes.)
There are also, other inputs to the TBCM (e.g. like the ignition circuit, the TBCS, etc.) Several of these are
used for other diagnostics and tests made by the TBCM’s program. Each of these inputs will generate a
code, if a failure is detected by the TBCM, ECM or the BCM. The TBCS is used to adjust the gain and
manually activate the Trailer Brakes.
There is an output to the Driver Information Control display panel to show a trailer connection and gain
settings, etc.. There is another output to the Trailer Brakes (i.e. The TBCM tells the TBCR how much
voltage to apply to the trailer brakes, based on the amount of Brake Master Cylinder Pressure being
applied to the vehicle’s brake system.)
Component Locations
The TBCM and The TBCR are located on the inner driver side frame rail near the rear tire under the
cargo box. The TBCS is on the lower dash. The Master Cylinder Pressure Sensor is located on the Master
Cylinder, under the hood. The Stop Lamp Switch is located near the brake pedal.
Component Programming
The TBCM has an internal program in it to facilitate the data communications and scale the braking, and
control the TBCR, among other things. If the TBCM is ever replaced, it has to be reprogrammed.



GM’s Integrated Trailer Brake Control System Description

Component Powering (Two B+ Circuits)
For the first B+ circuit, there is a Red/Black wire that needs to be connected to Stud #2, which is on the
front of the under-hood fuse box. Fuse 58 fuses this circuit. If the fuse is installed and working, you
should see >+12VDC on Stud 2. This provides power to the TBCR. When the TBCR is switched on by the
TBCM this +12 VDC is indirectly fed to the trailer brakes via the TBCR. This wire typically comes hooked
up and fused. However, on some models it may not have been hooked up and/or not fused.
Now here is a catch, … There are three Red/Black wires near the under-hood fuse box. Only one goes to
the Trailer Brakes. Two are Aux Power for charging trailer batteries. The two Aux power wires are
typically taped up to wiring harnesses. The Red/Black wire for the Trailer Brakes typically comes hooked
up to Stud 2. (Mine was hooked up.) If the ITBC system’s Red/Black wire is not hooked up, then you have
to find it and hook it to Stud 2. But, do not confuse it with the other two Red/Black Wires used for Aux
Power.
The two Aux power wires are located as follows:
There is one Red/Black Aux Power wire taped to the harness between the fender and under-
hood fuse box. (This wire was even labeled Aux Power on mine, which is confusing because it is
not the Aux Power wire to the Towed Trailer connector on the rear bumper.) This one powers
the Aux Power to the portion of the trailer harness that feeds the front of the Cargo box for 5
th

wheelers/campers. An added harness has to be plugged in for this, on the other end. This is not
the wire you need to fully power the ITBR.
The second Red/Black Aux Power Wire is taped to a wiring harness between the under-hood
fuse box and the engine. It may actually be right under the fuse box. Mine was. Again, this is not
the wire for the TBCM. This is an Aux Power wire that runs all the way back to the trailer
connector to charge a towed trailer’s batteries. This is not the wire you need to fully power the
ITBR.
(If you want to hook up either one of these to charge batteries, you hook it to Stud 1 and fuse it
with 40 Amp fuse.)
So that leaves a third Red/Black wire to power the TBCR. This remaining Red/Black wire has to be
hooked up to Stud 2 and fused. If it was not hooked up by the manufacturer, then it is taped to a
harness someplace close to the under-hood fuse box. It gets hooked up to Stud 2 and fused with a 30
amp fuse.
There is a second B+ circuit that needs to be energized for the Trailer Brake System to work. This is a
Red/White wire. This wire is already hard wired to the under-hood fuse box. However, Fuse 19 fuses this
circuit. This fuse typically installed by the manufacturer. But, check it to make sure it is still good.

GM’s Integrated Trailer Brake Control System Description

ITBC system Troubleshooting
To troubleshoot w/o a Tech II, all you can do is check the connections and look for the B+ voltages at
each of the three main components. So, you check all grounds at all three components. Then you check
the Red/Black wire at the TBCR and the Red/White wire at the TBCM for +12VDC. You also can check the
serial data connector contacts, but I doubt that these are a problem because the truck is new.
If the ITBC system is NOT working on delivery, I suspect that the Red/Black wire for the ITCR is not
hooked up or a fuse is missing.
If you have all the fuses in and the correct Red/Black wire fused and attached to Stud 2, then I would say
it is time to go into the dealer to get the codes read. It is difficult to get on all the grounds and B+ wires
for testing and why spend all that time and effort only to find out the BCM or ECM, etc may be at fault.
If the trailer works on another truck, it is safe to assume the trailer is not the problem. However, this
does not rule out a problem in your truck’s trailer connector. The truck’s connector is subject to
moisture and the resulting corrosion. My trailer’s running lights blew a fuse because of moisture in the
connector, the third week I had the truck.
Most of the time trailer brake problems are found at the connectors or the other end of the trailer’s
harness. Also, trailer brakes often short in the trailer wheels. That is why fuse 58 in the truck is there.
Sometimes the trailer harness also loses it connection in the Junction box located someplace on the
trailer (at the other end of the harness.)
I wrote about GM’s Red/Black wire fiasco in a RV magazine. Check out the bottom part of the
Article that results from the below link. But, this document has far more detail.
http://betterrving.com/Article/RV_Living/RVing_with_Len

This information is a compilation of information stated in the GM Tech Manual, which is sparse to say
the least. Also, I tried to put the information in terms that can be used in the field. Bottom Line: I am not
responsible for its content. However, comments for improvement and other suggestions for
improvement may be sent to [email protected]. Maybe after we all kick this around for a while and add
our own personal insights, we’ll get a good working aid going here.

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