GMC Yukon 2023 Owner's Manual page 301

300 Driving and Operating
Trailering App System will not display a
Trailer Detection Alert to the user when a
trailer is connected.
When a trailer is connected and the vehicle
is off, the Trailering App System will
periodically pulse the lighting circuits of the
trailer to verify it is still connected. The
trailer lights may periodically flash as a
result of this trailer connection detection.
These flashes may be more visible in dark
ambient light environments. The flashing or
flickering lights are a normal condition and
the Trailering App System has built-in
protections to prevent the battery from
draining. When Theft Alert is enabled, the
frequency and pattern of this flashing will
change.
If a connected trailer becomes disconnected,
a message about the trailer disconnect will
appear on the DIC immediately (if vehicle is
on) or the next time the vehicle is turned on
(if trailer was disconnected while vehicle is
off). Check your trailer connection if needed.
Connection Problem
If any of the trailer connections are lost, a
message about the connection issue will
appear on the Driver Information Center
(DIC). The infotainment display will also
show the connection issue in the Lights
Status view.
Connection Trailer Lighting Faults Detected
The Trailering App System monitors for
electrical faults on the trailer lights.
A message about the lighting issue will
appear on the DIC. The infotainment display
will also show the lighting issue in the
Lights Status view. Repair your trailer lights
if needed. A trailer lighting issue is not
covered by your GM warranty.
The Running Lights connection may not
detect partial outages. Activate the light test
to check all trailer lamps. See Light Test
following.
Light Test
Touch Start Light Test to cycle the trailer
lights on and off to determine if they are
working. The test follows this sequence:
1. The running lights turn on first and
remain on throughout the sequence.
2. The brake lights turn on for about
two seconds.
3. The left turn signal light flashes three
times.
4. The right turn signal light flashes three
times.
5. The reverse lights turn on for about
two seconds.
6. Steps 2-5 repeat for approximately on
minute and 45 seconds, or until the test
deactivates.
Touch Stop to stop the test. The test will
automatically end after one minute and
45 seconds.
The sequence also deactivates when any of
the following occur:
The vehicle is turned off.
The transmission is shifted out of
P (Park).
The brake pedal is pressed.
The turn signal is activated.
The hazard warning lights are activated.