Bulletin No.: PIT5404F
Published date: 11/7/2019

Preliminary Information
PIT5404F Squeak Chirp Whistle Rattle Type Noise from Rear of
Vehicle (Passive Exhaust Valve) or Bu eting Vibration Drone
Exhaust Tone Change Body Pressure Booming (AFM Exhaust)
Models
Brand:
Cadillac

Model
Years:

Model:
Escalade

VIN:
from

Engine:

to

Transmissions:

2015 - 2017

All

All

6.2L

All

Chevrolet Silverado 1500

2014 - 2017

SOP

12/14/2016 for Plants G and
Z*

4.3L or
5.3L

All

Chevrolet Suburban

2015 - 2017

SOP

7/1/2016

5.3L

All

Chevrolet Tahoe

2015 - 2017

SOP

7/1/2016

5.3L

All

GMC

Sierra 1500

2014 - 2017

SOP

12/14/2016 for Plants G and
Z*

4.3L or
5.3L

All

GMC

Sierra 1500
Denali

2014 - 2017

All

All

6.2L

All

GMC

Yukon Denali

2015 - 2017

All

All

6.2L

All

* For Build Plant Information See 11th Position of VIN
Involved Region or
Country:

North America and North America Export Regions
Some customers may comment on any of the following concerns:
- Squeak, whistle, rattle or chirp type noise from the rear of the
vehicle
- Exhaust tone change or exhaust drone type noise
- Buffeting vibration or body pressure booming

Condition:

These concerns may be most noticeable when the engine transitions in
and out of Active Fuel Management (AFM) mode, or while the engine is
operating in V4 (4-cylinder) Active Fuel Management (AFM) mode in the
1,100-1,400 RPM range.
While some slight changes in exhaust tone and/or vibration/drone type
noises can be normal when the engine is in V4 mode, there have been
complaints of them being excessive.
Note: If the concerns are excessive, they may excite the roof sheet
metal and compound the issue. (See the latest version of PIT5318.)

Cause:

These concerns may be caused by the Passive Exhaust Valve (PEV),
located in the exhaust muffler and tail pipe assembly, making noise or
effecting exhaust tone, or may be caused by an exhaust leak at the
clamp joint.

Correction for 4.3L and 5.3L ONLY:
1: Verify the concern is present Only during V4 mode. (During evaluation, monitor Instant
Fuel Economy screen in DIC, or on scan tool to determine V4 vs V8 mode.)

1.1: Once the concern is duplicated in Drive, shift trans into manual 5th or 6th to operate
in V8-only mode and re-test under same conditions.
1.2: Switch back and forth between Drive and manual 5th or 6th to turn concern On/Off.
Note: Using a Pico scope, AFM V4 mode operation will display as E2 for a V8 engine, and E1
for a V6 engine.
If the concern is qualified to be present only during V4 mode operation, an updated exhaust
to address this concern is now available for vehicles built before the build dates listed. See
Notes following before proceeding to Parts table in this PI.
If the noise is not present during V4 mode operation, it may occur during transitions
between V4 and V8 modes - as a Test Only, perform the following diagnostic steps:
2: Temporarily lock the PEV in the open position, as shown in the latest version of PI1201,
and re-evaluate. If the noise is eliminated or changes greatly in severity, an updated
exhaust and PEV to address this concern is now available for vehicles built before the build
dates listed. See Notes following before proceeding to Parts table in this PI.
Note: The updated design exhaust has the passive exhaust valve (PEV) located in front of
the muffler; the original design exhaust has the PEV located behind the muffler. Proceed to
the Parts Information table in this PI.
Note: Ensure there are no leaks at the exhaust band (Norma) clamp joint after the new
exhaust has been installed. It has been found in some cases that a leak at the clamp joint
could allow some level of exhaust tone change or exhaust vibration/drone type noise and/or
buffeting vibration or body pressure booming to occur. Refer to latest version of PIP5442. If
no exhaust leak is found, replace the exhaust. Proceed to the Parts Information table in this
PI.

Correction for 6.2L ONLY:
1: Verify the concern is present Only during V4 mode. (During evaluation, monitor Instant
Fuel Economy screen in DIC, or on scan tool to determine V4 vs V8 mode.)
1.1: Once the concern is duplicated in Drive, shift trans into manual 5th or 6th to operate
in V8-only mode and re-test under same conditions.
1.2: Switch back and forth between Drive and manual 5th or 6th to turn concern On/Off.
Note: Using a Pico scope, AFM V4 mode operation will display as E2 for a V8 engine.
(Frequency will likely measure in the 36-48 Hz range depending on speed.)
If the concern is qualified to be present only during V4 mode operation, continue further
with this PI.
If the noise is not present during V4 mode operation, it may occur during transitions
between V4 and V8 modes – as a Test Only, perform the following diagnostic steps:
2: Temporarily lock the PEV in the open position, as shown in the latest version of PI1201,
and re-evaluate. If the noise is eliminated or changes greatly in severity, the PEV is the
source of the noise.
Note: There have been continuous improvements made to the 6.2L passive exhaust valve
(PEV) to help address squeak, chirp, whistle, rattle type noises emanating from the PEV.
Refer to the parts catalog.
3. If the condition is present regardless of V4 or V8 mode, and was not changed with the PEV
test, refer to published PI diagnostics.

Exhaust System Inspection:
1. Ensure there are no leaks at the exhaust band (Norma) clamp joint. It has been
found in some cases that a leak at the clamp joint could allow some level of exhaust
tone change or exhaust vibration/drone type noise and/or buffeting vibration or body
pressure booming to occur. Refer to latest version of PIP5442.

2. If no leaks were found at the exhaust band clamp joint, inspect exhaust system
components for the following; both COLD and HOT; in NEUTRAL, FORWARD and
REVERSE gears:
Loose and/or missing fasteners
Heat shields damaged
Joints and/or couplings not properly seated: Nuts, bolts, studs, clamps, straps
Bracket and/or insulator mounting concerns
Inadequate clearance to body and/or chassis components
Improper alignment
Disconnected and/or missing insulators
Cracked, dry-rotted, and/or oil-soaked insulators
Stretched, twisted, broken, torn, and/or collapsed insulators
Bent, twisted, cracked, and/or deformed brackets
3. Repair and/or replace exhaust system components as indicated by the inspection, then
re-evaluate the condition.

Exhaust and Powertrain Settling Process:
Incorrectly seated and/or aligned powertrain components and/or exhaust system
components may create a transfer path into the passenger compartment. Perform the
following procedure to re-bed the powertrain/exhaust:
1. Loosen, but do not remove, the engine mount to frame bolts and the
transmission/transfer case mount to crossmember nuts.
2. Loosen, but do not remove, exhaust system hangers.
3. Ensure that the exhaust flexible coupling, if equipped, moves freely.
4. With the vehicle on the ground at ride height, set the park brake and apply the base
brake.
5. Turn Traction Control Off, and brake torque in Drive and Reverse – engine at operating
temperature – then place in Neutral and turn engine Off.
6. Using Only Hand Tools, tighten all of the loosened fasteners to specs with the
powertrain in a relaxed position, then ensure exhaust hangers are seated correctly.

Exhaust Test:
If after performing the above suggestions, the concern has not been resolved or improved,
as a Test Only, swap the exhaust muffler and tail pipe assembly from a known good truck. If
this corrects or improves the concern, replace the exhaust muffler and tail pipe assembly on
the concern vehicle.

Active Noise Cancellation (ANC) System Operation:
The Active Noise Cancellation system is a method used to reduce the perception of
certain undesirable sounds generated by the engine into the vehicle cabin. If the
system is not working or working incorrectly this can be the cause or a contributor of
the issue.

Main components of ANC system:
3 microphones in the vehicle headliner.
A discrete engine speed (RPM) signal from the engine control module to the amplifier
Active Noise Cancellation electronics and software integrated into the audio amplifier
The vehicle speaker system, connected to the amplifier, to output the desired
cancellation frequencies
The ANC system is operational under the following conditions:
The amplifier has passed all self-diagnostic checks
All doors are closed
Battery voltage is between 9.5 V and 16 V
The vehicle cabin temperature is less than 140°F (60°C)
Engine speed is between 550 and 3000 RPM

ANC system Diagnostic Tips:
1. Inspect for any aftermarket audio components. If the audio system has been altered
this will hinder ANC operation and will cause increased exhaust drone.
2. Inspect for anything inside the truck that may be blocking the speakers and/or
microphones.
3. Inspect for any DTC's; example: B0560, B1277, B127C, B127D, door ajar issues/DTC's,
etc.
4. Disable the ANC system by removing the AMP fuse. If the exhaust drone noise improves
there may be an issue with the ANC system. Some examples of system issues have
been: faulty speaker or subwoofer, speaker or subwoofer improperly wired (-/+ wires
backward), speaker or subwoofer inoperative, microphone out of position in headliner,
etc.
Note: The Audio System Diagnostic CD EL-50334-6 contains audio tracks that can be
used to test the speakers.
If the concern is qualified to be present only during V4 mode operation, but is deemed to be
normal by comparing to a like vehicle with 6.2L, and no issues were found following the
exhaust inspection, settling at test steps, and the ANC system has been verified to be
operating correctly, then no further repairs should be made, as this is a normal
characteristic.

Parts Information
The following parts apply to 4.3L or 5.3L equipped vehicles only:
Part Number
23385910
23385911
84020521

84020522

84020523

84020524

Description
Muffler Ams-Exh (W/ Exh Pipe) – 5.3L
Long Wheel Base SUV CK15906
Muffler Ams-Exh (W/ Exh Pipe) – 5.3L
Short Wheel Base SUV CK15706
Muffler Ams-Exh (W/ Exh Pipe) – 4.3L
LV3, 5.3L L83 Crew Cab 6' 6" Bed
CK15743
Muffler Ams-Exh (W/ Exh Pipe) – 4.3L
LV3, 5.3L L83 Crew Cab 5' 8" Bed
CK15543
or
4.3L LV3, 5.3L L83 Double Cab 6' 6" Bed
CK15753
Muffler Ams-Exh (W/ Exh Pipe) – 4.3L
LV3, 5.3L L83 Regular Cab 8' Bed
CK15903
Muffler Ams-Exh (W/ Exh Pipe) – 4.3L
LV3, 5.3L L83 Regular Cab 6' 6" Bed
CK15703

Qty
1
1
1

1

1

1

Warranty Information
For 6.2L equipped vehicles, the correction for this concern may be one of several repairs described above. For
vehicles repaired under warranty, please use the appropriate warranty labor operation based on the actual cause

and repair.
For 4.3L or 5.3L equipped vehicles only, with exhaust replacement:
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

4081798*

Pico Scope Exhaust Vibration Measurement and
Evaluation

.3 hr

4051980

Exhaust Mu er with Resonator, Exhaust, and Tail
Pipe Replacement

Use Published Labor Operation
Time

* This is a unique labor operation for bulletin use only.
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
drone

Version History
Version

Modi ed

6
05/01/2015 — Created on
07/01/2016 — Updated Model years
08/18/2016 — Updated Repair information
01/26/2017 — Updated Model Year
06/16/2017 — Updated Labor Times
04/24/2019 — Updated Model Years
11/7/19 — Updated Model Years

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