Bulletin No.: PIT5404D
Published date: 06/16/2017

Preliminary Information
PIT5404D Squeak Chirp Whistle Rattle Type Noise from Rear of Vehicle (Passive Exhaust Valve) or
Buffeting Vibration Drone Exhaust Tone Change Body Pressure Booming (AFM Exhaust)
Models
Brand:

Model:

Model Years:

VIN:
from

Engine:

to

Transmissions:

Chevrolet

Suburban

2015 - 2016

SOP

07/01/2016

5.3L

All

Chevrolet

Tahoe

2015 - 2016

SOP

07/01/2016

5.3L

All

Chevrolet

Silverado 1500

2014 - 2017

SOP

12/14/2016 for Plants G and Z*

4.3L or 5.3L

All

GMC

Yukon

2015 - 2016

SOP

07/01/2016

5.3L

All

GMC

Sierra 1500

2014 - 2017

SOP

12/14/2016 for Plants G and Z*

4.3L or 5.3L

All

Cadillac

Escalade

2015 - 2017

All

All

6.2L

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

Supersession Statement
This PI was superseded to update labor time. Please discard PIT5404C.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
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.
2.
3.
4.
5.

Loosen, but do not remove, the engine mount to frame bolts and the transmission/transfer case mount to crossmember nuts.
Loosen, but do not remove, exhaust system hangers.
Ensure that the exhaust flexible coupling, if equipped, moves freely.
With the vehicle on the ground at ride height, set the park brake and apply the base brake.
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

Description

Qty

23385910

Muffler Ams-Exh (W/ Exh Pipe) – 5.3L Long Wheel
Base SUV CK15906

1

23385911

Muffler Ams-Exh (W/ Exh Pipe) – 5.3L Short Wheel
Base SUV CK15706

1

84020521

Muffler Ams-Exh (W/ Exh Pipe) – 4.3L LV3, 5.3L L83
Crew Cab 6' 6" Bed CK15743

1

84020522

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

1

84020523

Muffler Ams-Exh (W/ Exh Pipe) – 4.3L LV3, 5.3L L83
Regular Cab 8' Bed CK15903

1

84020524

Muffler Ams-Exh (W/ Exh Pipe) – 4.3L LV3, 5.3L L83
Regular Cab 6' 6" Bed CK15703

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:
Labor Operation

Description

Labor Time

4081798*

Pico Scope Exhaust Vibration Measurement and
Evaluation

.3 hr

4051980

Exhaust Muffler 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

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