GMC Yukon 2021 Owner's Manual page 302

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
Connection Status view. Repair your trailer
lights if needed. A trailer lighting issue is
not covered by your GM warranty.
Diagnose View
Touch Diagnose to see more information
about the connection problem.
This view will display the names of the
trailer connector pins, a graphic of the trailer
connector, and a graphic of the back of the
trailer.
Any connector pin that failed will be amber
color, and the location of the corresponding
connection will be highlighted on the
graphic of the back of the trailer.
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
one 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 ignition is turned off.
The transmission is shifted out of P (Park).
The brake pedal is pressed.
The turn signal is activated.
Driving and Operating
The hazard warning lights are activated.
Tires
1. Trailer Tire Pressure/Temperature
Tire Pressure and Temperature
If the TTPMS sensor-to-vehicle learn process
was completed, the status view will display
the current tire pressure and temperature of
the trailer tires related to the active Trailer
Profile. If a tire s pressure is low or high, the
color of the pressure value will be amber.
If a sensor malfunctions, the values are
dashed lines. If the screen displays Service
Tire Pressure Monitoring System , the
vehicle needs to be taken to a dealer for
service.
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