17NA172

File in Section:
Bulletin No.:
Service Bulletin
Date:
17-NA-172
October, 2017
INFORMATION
Subject:
Rear Suspension Sagging or Sitting Low, Vehicle Not Level After Sitting Overnight
Brand:
Model:
Cadillac
XTS
Model Year:
VIN:
from
to
from
2013
2018
Engine:
Transmission:
All
All
to
Involved Region or Country
North America and N.A. Export Regions
Additional Options (RPOs)
Equipped with Rear Air Suspension (RPO F38)
Condition
Vehicles in new car inventory may be observed or some customers may comment that
the rear of the vehicle is riding/sitting low, vehicle sagging, vehicle not level, suspension
bottomed out, etc.
Cause
Review probable causes below.
Field feedback has identified additional causes/
appearance of leaks in the air suspensions system that
are not found in service information. If DTCs are
present, follow service information. If not, follow the
procedure below in sequential order.
Verify Airlines are Inserted Correctly –
Generally on Vehicles with Less Than
5000 Miles (8000 Km)
Caution: Prior to any visual and physical inspections
of the airlines, the system should be depressurized
according to SI. Failure to depressurize the system may
cause personal injury or damage to the vehicle.
4799440
Copyright 2017 General Motors LLC. All Rights Reserved.
The air suspension system is very robust and if a
vehicle is reported to have an air suspension failure in
the first 5000 miles (8000 km), it is likely that the airline
connections at the air springs were assembled
incorrectly during the manufacturing process. The
design of the airline does not allow for it to be partially
inserted. It will either be fully seated or sitting loose in
the fitting. There should be about 3-4 mm from the face
of the valve to the notch in the airline (Dimension X
above).
Page 2
October, 2017
Physical Inspection
Bulletin No.: 17-NA-172
Airline Insertion
In order to check if the airline is seated, follow the
below steps:
1. Depressurize the air suspension system according
to SI. Failure to depressurize the system may
cause personal injury or damage to the vehicle.
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1. The airline should be inserted until resistance is felt
in the system. The photo above shows how far the
line must be inserted before the resistance begins.
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2. Use two fingers to grasp the airline. Do NOT use
tools such a pliers or clamps.
3. Gently pull the airline outward. If the airline does
not pull entirely out of the fitting, it is seated
correctly. If the airline comes out it must be
reinserted.
Correct Airline Insertion
The fittings used on the air suspension are generally
similar in nature to a “Push to Connect Fitting.” The
operator pushes the air-line until resistance is felt and
continues to insert the air line until it bottoms out. At this
point the air-line is to be gently and firmly pulled out
(not yanked). This causes a collet to bite into the
air-line causing it to seat permanently.
The problem that commonly occurs is, once the initial
resistance is felt during the airline insertion, the
operator believes the airline has bottomed out. In reality
the airline is just sitting in place and could be worked
out of the fitting over time.
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2. The airline should continue to be inserted until it
bottoms out and can no longer be inserted any
further.
Bulletin No.: 17-NA-172
October, 2017
Page 3
4799446
3. The airline is then gently pulled out and the collet
will seat.
4. Once the airlines are seated, pressurize the
system according to SI.
Verify Trim Height is Set Correctly
The air suspension will lift the vehicle to a defined trim
height. If the air suspension system is functioning
correctly according to diagnostics in Service
Information, then the trim height might need to be
calibrated. Please follow the trim height calibration
procedure in SI.
Note: Anytime suspension components are replaced
on the rear of the vehicle, the trim height needs to be
recalibrated. Please check the vehicle history for any
previously done suspension work.
Verify if a Normal Condition is Being
Perceived as a Leak
It is important to understand normal depressurization/
leaking of the air suspension system prior to diagnosis
of failures. The system will exhaust pressure within 30
minutes after the ignition is turned off to lower the
vehicle after unloading. In a temperature-controlled
environment, the leakage of the complete load leveling
system will not result in more than 1.4 mm (0.05 in) drop
of rear suspension height at GVWR during a 24 hour
period. If the outdoor temperature drops from +20°
C (+68°F) to −5°C (+23°F), the rear R height may drop
as much as 25 mm (1 in). However, the Air Suspension
System should return to the specified R height when
the ignition is again cycled to ON.
4804659
R Height: The vertical distance from the ground to the
top of the wheel opening through the center line of the
rear wheel.
If the suspension is sitting low, start the vehicle and
allow the compressor to pressurize the system. It will
not take more than a couple of minutes to bring the
vehicle up to the correct ride height. Measure the
current R Height. Allow the vehicle to sit for a 24 hour
period and measure the R Height again. If
temperatures have not changed for 24 hrs there should
be minimal drop. If there was a large temperature drop
(up to 45°F) in the 24 hr period ensure the drop is less
than 1 inch. A height change greater than 1 inch should
be treated as a leak in the system.
Note: The Air Suspension System must have a voltage
supply of at least 12.6V to operate properly.
Warranty Information
For vehicles repaired under the Bumper-to-Bumper
coverage (Canada Base Warranty coverage), use the
following labor operation. Reference the Applicable
Warranties section of Investigate Vehicle History (IVH)
for coverage information.
Labor
Operation
Description
Labor Time
8080308*
Verify Airlines are Inserted
Correctly
0.3 hr
Add
Trim Height Calibration
0.2 hr
*This is a unique Labor Operation for Bulletin use only.
Version
2
Modified
October 11, 2017 – Updated the Subject.
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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