18NA104

File in Section:
Service Bulletin
-
Bulletin No.:
18-NA-104
Date:
April, 2018
INFORMATION
Subject:
Brand:
Cadillac
Hoot, Whine, Buzz, Hiss Noise Coming from Vehicle After Engine is Shut Off
Model:
Model Year:
VIN:
from
to
Engine:
Transmission:
from
to
ATS-V
2016
2019
3.6L (LF4)
All
CT6
2016
2019
3.0L (LGW)
All
CTS
XTS
2014
2019
3.6L (LF3)
All
Involved Region or Country
North America and N.A. Export Regions
Condition
Some customers may comment that they hear a hoot, whine, buzz, hiss type noise for
approximately 5 seconds after shutting off the vehicle. This noise may be more noticeable
with the hood open.
Upon inspection, the technician may find the noise may be more noticeable near the
turbocharger wastegate regulator solenoids.
Cause
This is a normal characteristic of the turbocharger vacuum system equalizing to ambient
conditions after shutdown. The noise may be heard more noticeably around the
wastegate regulator solenoids.
When the engine turns off, the vacuum to the turbocharger wastegate actuator is
released, and the air rushes back through the wastegate regulator solenoid (LH and RH
operated separately). This air can cause an internal diaphragm in the solenoid to
resonate, creating an audible noise until the air is fully released (less than 5 seconds).
The resonant frequency of each individual part differs with the design tolerances of the
solenoid assembly. This is why one part may exhibit the noise, while another will not.
Service Procedure
Parts Information
This is a normal characteristic of the turbocharger
vacuum system. This audible sound is normal, and the
customer can be assured that there is no problem with
the function of the wastegate regulator solenoid. The
potential for an audible noise is a function of the
resonant frequency of the diaphragm in the new
replacement part.
No parts needed for this condition.
Version
1
Modified
Released April 5, 2018
Customer Information
Please communicate to the customer this condition is a
normal operating characteristic of their vehicle. Please
share this information with the customer, including a
copy of this message.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.
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