Bulletin No.: PIT5801D
Published date: 06/11/2024

Preliminary Information
PIT5801D Diagnostic Tip / Vehicle Sits Unlevel / Leans / Sags / Leveling
Unavailable Message / Speed Limited Message / Service Air Suspension Message
/ DTC C1190 C1191 C1192 C1193 C1187 C1188 C1189 C118A C118B C118C C118E
C118F
Models
Brand:

Model:

Model Years:

Cadillac Escalade Models 2021
Chevrolet Suburban
2021
Chevrolet Tahoe
2021
GMC
Yukon Models
2021

-

2024
2024
2024
2024

VIN:
Engine: Transmissions:
from to
All
All All
All
All
All All
All
All
All All
All
All
All All
All

Involved Region or
Country

North America

Additional Options
(RPO)

F47 - Air Ride Suspension

Some customers may notice one or more of the following conditions related
with the air ride suspension.
Condition

Cause

- Vehicle suspension trim height is too high or too low at one or more corners.
- DIC Messages "Leveling Unavailable", "Service Air Suspension" and/or "Speed
Limited"
- DTC's: C1190, C1191, C1192, C1193, C1187, C1188, C1189, C118A, C118B,
C118C, C118E, C118F

The cause of these concerns could be an air line not being fully inserted into its
air line fitting at the air springs, air controller or reservoir tank, see PIT5923A
for component naming. An air line that is not fully inserted into its fitting
can leak air and cause an air spring to be under inflated creating a lean/sag to
one side. But if an air line is not fully inserted at an AIR SPRING fitting it could
cause the air spring to be OVER inflated. If an air spring is OVER inflated it
can make the opposite side of the vehicle appear to be low and mislead
diagnosis to the side that looks like it is sagging/low. It can be hard to
understand why an air line, which is not fully inserted into the fitting at the air
spring, could cause an air spring to be over inflated. The following info will
provide some details on why this can happen and how to test and diagnose this
concern.
To help understand why an air line, which is not fully inserted into the fitting at
the air spring, can cause an over inflated air spring you will need to understand
how the air spring fitting is made/works. The air line fitting, at each air spring,
is unique, and contains a one way check valve within the fitting. These unique
air line fittings, with the one way check valve, are ONLY used at each of the air
springs. The air line fittings at the air suspension controller and reservoir tank
do not contain any check valves, and are a straight pass through fitting.
The reason the air spring fittings have this unique check valve, is to hold air
pressure inside the air spring assembly, while the air line is disconnected from
the air spring. This keeps the air spring inflated for service and manufacturing
purposes. Once the air spring is installed in the vehicle and the air line is fully
inserted into the air spring fitting, the end of the air line will push open and hold
open the one way check valve. This will allow air to move in or out of the air
spring. When an air line is not fully inserted into the air spring fitting, it will not
hold open the one way check valve. When this happens, during an inflate
command, the air can pass the one way check valve to inflate the air spring, but
the check valve will not allow air to leave during a deflate command. This will
cause the air spring to become over inflated.
Because it is critical for the air lines to be fully inserted into the air fittings,
there are white marks on each air line to indicate when the air line is fully

inserted. These white marks can be useful to help indicate that the air
line is inserted far enough at the air suspension controller or reservoir tank,
but are NOT always a good indication that the air line is inserted far enough to
push open the one way check valve at the air spring fitting.
The air line must be inserted into the air fitting until it bottoms out AND the
white marks are going into the top of the fitting. Below is a picture of an air
line, at one of the air springs, which is NOT fully inserted (1). In this case, it is
evident that the white markings are not actually going into the fitting. The
second photo below shows the air line after it was fully inserted (2). You can see
the white marks are now down into the top of the air line fitting (2) and the air
line is bottomed out in the fitting.
NOTE: It is recommended to push the line into the fitting as far as it will go. At
least part of the white marking MUST be into the top of the fitting. Remember,
when inserting an air line into an air spring fitting, just because the white marks
are in the fitting, does NOT always mean that the line is fully inserted and
pushing the one way check valve open.
For additional examples, see the third photo below. This is a picture of the air
lines at the air controller. In this example, there are several fully seated lines as
shown in call out 4. Each of these lines is fully seated as indicated by the fact
that the white lines are partially covered by the air line fitting itself. Call out
3 is an example of a line that is not fully seated. In call out 3 you can see the
white marking is not into the air line fitting as it should be.

Correction:
Note: The purpose of this PI is to focus on the air line connections at the air springs, air controller and
reservoir tank. It is understood that other issues with the air suspension system can cause over or under
inflated air springs. In addition to this PI, please follow all published SI diagnostics and safety procedures
when working on the air suspension system.
In most cases, performing a very thorough inspection of each air line at the four air springs, air controller
and reservoir tank will prove to be the fastest and most fruitful way at discovering the root cause within
the system. Make sure at least the white marking on each air line is into the top of the fitting and that the
air line is bottomed out in the fitting, as both shown and described above. If an air line is not fully
inserted, then push the air line into the fitting until it is fully inserted and the white marking is into the top
of the fitting. In most cases, there is no need to loosen the air line fitting to fully insert the air line, just
push the line info the fitting.
NOTE: Remember, when inserting an air line into an air spring fitting it must be inserted fully to open the
one way check valve. Just because the white marks are into the top of the fitting does NOT always mean
the line is fully inserted and holding open the one way check valve.

Continue with the following testing if the above inspection has been completed, but the vehicle is still
unrepaired.

Testing for an air spring that is over inflated and will not deflate
1. Primary Test to determine if an air spring can deflate:
-

Ensure the battery is fully charged
Vehicle sitting on a flat level surface with the air springs inflated
Close all doors, hood and liftgate
Ignition on and engine off

- Start with one corner and measure the trim height from the ground to the top of the wheel well opening
for that one corner and document the measurement.
- Use GDS2 and go into Module Diagnostics> K5 Auto Level Control Module>Control Functions > Short
Term Deflate > then select the corner previously measured and perform 4 short term deflate commands.
- After completing the 4 short term deflates, for that one corner, go back and remeasure the trim height
at that corner and compare the two measurements.
- Typically, the vehicle will lower at least 10 mm's or more. If the vehicle trim height is decreasing, then
continue the same steps above for each of the remaining corners. It is important that you only do ONE
corner at a time, or incorrect results will occur.
-If the vehicle does not lower after performing the 4 Short Term Deflates, then suspect the air line is not
fully seated at that air spring. In some cases, if the air spring is full of air and under high pressure, it can
be very difficult to push the air line into the air fitting. This is because the one way check valve is being
pushed closed by the high pressure air inside the air spring. In these cases, try lifting the vehicle by the
frame so the suspension is fully extended. Then while using extreme care, push the air line into the fitting
with a suitable tool. If the air line gets kinked, pinched, or damaged, it will need to be replaced.
2. Secondary Test to determine if an air spring can deflate:
- Use GDS2 and go into Module Diagnostics> K5 Auto Level Control Module>Data Display>Pressure Data
and view the pressure data for at least 5 minutes. During that 5 minutes GDS2 is polling each air spring
and the reservoir tank for it's pressure reading. If an air line is not fully inserted into one of the air spring
fittings, you will notice the air pressure for that corner will be slowly decreasing (yellow graph line, shown
below) while the pressure for the other corners is holding steady.
- If the air pressure is slowly decreasing for a particular corner, as shown below, then suspect the air line at
the air spring is not fully inserted. In some cases, if the air spring is full of air and under high pressure, it
can be very difficult to push the air line into the air fitting. This is because the one way check valve is
being pushed closed by the high pressure air inside the air spring. In these cases, try lifting the vehicle by
the frame so the suspension is fully extended. Then while using extreme care, push the air line into the
fitting with a suitable tool. If the air line gets kinked, pinched, or damaged, it will need to be replaced.

Testing for an under inflation
- Apply soapy water to the air lines and fittings at the air spring and air manifold block, while looking for
any leaks. If the air pressure is too low in the air spring, then perform the following steps to add air into
the suspect corner, while inspecting for any leaks.
- Ensure the battery is fully charged
- Close all doors, hood and liftgate
- Ignition on and engine off
- Connect GDS2 and go into the Automatic Level Control Module > Control Functions > Short Term Inflate >
then select the suspect corner (LF, RF, LR, RR) and perform short term inflate commands, as needed.
Note: If the vehicle was driven for a period of time with no air pressure in an air spring, it may have
damaged the air spring. Once the vehicle is repaired, a thorough inspection of the inflated air spring

should be performed. If any damage is found, or if it is uncertain that any damage occurred, then the air
spring should be replaced.

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

8020980

Automatic Level Control Module Replacement

Use Published
Time

8021000

Automatic Level Control Air Supply Reservoir Replacement

Use Published
Time

8044650
8044651

Rear Shock Absorber, Shock Absorber Component, Spring or Seat Use Published
Air Line
Time
Rear Shock Absorber, Shock Absorber Component, Spring or Seat Use Published
Air Line - Both Sides
Time

8033620
8033630

Front Shock Absorber, Shock Absorber Component, Spring or
Seat Air Line - Left Side
Front Shock Absorber, Shock Absorber Component, Spring or
Seat Air Line - Right Side

Use Published
Time
Use Published
Time

Version History
Version

5

Modified

11/30/2020 - Created on.
04/19/2021 - Update to warranty sections
12/08/2021 - Update to the Correction, Warranty sections and
Model Years.
06/19/2023 - Update to the Models, Cause, and Correction
Sections.
06/11/2024 - Update to the model years.

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