Trailering Systems
2-53
Refer to the hill start assist system in the anti-lock
brake system description and operation document for
more information.
Trailer Sway Control
The trailer sway control can detect the vehicle yaw
instability, caused by an attached trailer. Refer to the
trailer sway control system in the anti-lock brake
system description and operation document for more
information.
Trailer Gain and Output Display
This display menu can be accessed by scrolling
through the DIC menu, or any time the trailer gain +/
−
button is depressed, or the manual trailer brake apply
lever is actuated. The trailer output is displayed from 0
to full output and indicates the output power provided to
the trailer brakes, relative to the gain setting.
After the electrical connection is made to a trailer
equipped with electric brakes or electric over hydraulic
brakes, the TRAILER CONNECTED message will be
displayed momentarily on the DIC. The Trailer Brake
Display Page can be selected on the DIC showing
TRAILER GAIN and OUTPUT, after all vehicle related
service messages are acknowledged by the driver.
Depending on which instrument panel cluster is in the
vehicle, the DIC may display dashed lines, a greyed out
display, or it may be blank signifying a disconnected
trailer or a trailer brake fault condition.
Trailer Brake Messages
The following indicators are used to inform the driver of
several different conditions:
Trailer Connected
This message will be briefly displayed when a trailer
with Electric or Electric Over Hydraulic brakes is first
connected to the vehicle. This message will
automatically turn off in about ten seconds. The driver
can also acknowledge this message before it
automatically turns off.
Check Trailer Wiring
This message will be displayed if:
•
The system detects that a trailer with Electric or
Electric Over Hydraulic brakes is connected to the
vehicle and then the trailer harness becomes
disconnected from the vehicle.
•
The trailer connection is recognized initially and
then a disconnect occurs while the vehicle is
stationary. This message will automatically turn off
in about thirty seconds. This message will also
turn off if the driver acknowledges this message
off or if the trailer harness is reconnected.
•
A disconnect of the trailer wiring harness occurs
while the vehicle is moving. The Check Trailer
Wiring message will continue until the ignition is
turned off. The message will also turn off if the
driver acknowledges this message off or it the
trailer harness is re-connected or repairs are
completed.
•
There is an electrical fault in the wiring to the
electric trailer brakes. The Check Trailer Wiring
message will continue as long as there is an
electrical fault in the trailer wiring. This message
will also turn off if the driver acknowledges this
message off.
•
A poor connection at the 7
–
way connector may
cause the Check Trailer Wiring message. Some
aftermarket 7
–
way trailer side connector adapters
or plugs may cause deformation or excessive
wear to the vehicle
’
s trailer terminals. It is
recommended that you use an OEM or Pollak
heavy duty 7
–
way trailer side connector adapter.
Service Trailer Brake System
This message will be displayed when there is a
problem with the trailer brake control system. The trailer
brake system may not be fully functional, or may not be
functioning at all. The trailer brake system is designed
to provide trailer braking, if possible, even when faults
prevent it from being fully functional. This reduced
functionality includes:
1. Providing trailer braking when the master cylinder
pressure or brake pedal switch are faulted.
2. Providing trailer braking when hill start assist and
trailer sway control communication is faulted.
3. Providing trailer braking when certain manual
trailer brake apply lever faults are present.
These conditions should be repaired to allow the trailer
brake system to be fully functional.
Trailering Diagnostic Tools
In some situations when diagnosing trailer lighting,
or integrated trailer brakes, it may be necessary to
connect the vehicle to a trailer to confirm proper
operation. Performing this activity may prove difficult in
the service environment since trailers are not often
available for diagnostic use, may have existing
electrical issues outside of the issues a technician is
attempting to diagnose, or simply may be too unwieldily
to connect for diagnosis.
With all this in mind, it may be helpful to build or create
a tool that can be plugged into the vehicle
’
s 7-way
trailer connector and simulate a connected trailer. This
tool would include park lamps, stop lamps, and a
reverse lamp for lighting and trailer tire pressure
monitoring diagnosis. It can be expanded to include
trailer brake magnets to diagnose integrated trailer
brake concerns. Also, an additional lamp can be
included to diagnose the B+ circuit to the trailer.
Trailer issues are NOT covered under warranty, but
these tools may be used to verify the vehicle is
functioning properly and to help the customer
understand and correct any trailer related issues if they
so choose.
2021 - Silverado 4500HD, 5500HD, and 6500HD Electrical Body Builder Manual
