PIC5979B

Bulletin No.: PIC5979B
Published date: 04/10/2019
Preliminary Information
PIC5979B Normal Characteristic - HVAC Temperature Varies from
Side to Side
Models
Brand:
Model:
Model Years:
VIN:
from
to
Engine:
Transmissions:
Cadillac
ATS
2013 - 2019
All
All
All
All
Cadillac
CTS Sedan (VIN A)
2014 - 2019
All
All
All
All
Supersession Statement
This PI was superseded to update Model Years. Please discard PIC5979A.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition / Concern
A customer may complain about the HVAC system discharge temperature to vary from side to side when the set
temperature is set to the same value.
Recommendations / Instructions
IMPORTANT: Do NOT replace components for this condition. Replacing the duct sensors or temperature motors
will not improve this situation.
It is normal for a dual zone or tri-zone HVAC system discharge temperature to vary from side to side when the set
temperature is set to the same value.
The upper duct sensors are placed in the outer parts of the ductwork and do not read the discharge temperature
from the center outlets. This can be made worse if the outboard panel outlets are shuto , which will cause the
duct sensors not to read properly. In a garage condition, with all of the outlets open after 10 minutes of idling all
of the outlets should stabilize within 6 degrees if measured in Celsius, or 12 degrees of each other if measured in
Fahrenheit.
Starting in the 2015 model year ATS and CTS vehicles, the Upper Duct Temperature Sensors are no longer used in
the control of the temperature and use a Virtual Duct Sensor control strategy. Starting in model year 2017 the
Upper Duct Temperature Sensors were removed from the ductwork.
Customer Information
Please communicate to the customer this condition is a normal operating characteristic of their vehicle. It will not
impact the designed performance or reliability of the vehicle. Please share this information with the customer,
including a copy of this message.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is
resolved without completing every step, the remaining steps do not need to be performed.
Additional SI Keywords
blower cold temp warm
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