21NA278

Bulletin No.:
Service Bulletin
Date:
21-NA-278
November, 2021
INFORMATION
Subject:
Diagnostic Strategy for Ticking, Tap or Rattle Noise from Engine with Possible Misfire,
Malfunction Indicator Lamp (MIL) Illuminated - DTCs P0300, P0301-P0306 and/or
P0016-P0019 Set
This bulletin replaces PIP5486H and PIP5493J. Please discard PIP5486H and PIP5493J.
Brand:
Buick
Cadillac
Chevrolet
GMC
Holden
Model:
Model Year:
VIN:
from
to
Engine:
(3.0L, 3.6L)
from
to
LaCrosse
2017
2019
LGX
Regal
2018
2020
LGX
ATS
2016
2019
LGX
CT5
2020
2022
LGY
CT6
2016
2020
LGW, LGX
CTS
2016
2019
LGX
XT5
2017
2022
LGX
XT6
2020
2022
Blazer
2018
2021
LGX
Camaro
2016
2022
LGX
Colorado
2017
2022
Acadia
Canyon
2017
2022
Acadia
2019
2020
Commodore
2018
2020
Involved Region or Country
Copyright 2021 General Motors LLC. All Rights Reserved.
—
—
LGX
Transmission:
—
LGZ
LGX
LGZ
LGX
North America, Europe, Uzbekistan, Russia, Middle East, Iraq, Israel, Palestine,
Argentina, Brazil, Bolivia, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay,
Venezuela, Japan, Cadillac Korea (South Korea), GM Korea Company, China, Taiwan,
Thailand, Singapore, Philippines, Australia/New Zealand, Egypt, Other Africa, South
Africa
Page 2
Condition
November, 2021
Bulletin No.: 21-NA-278
Some customers may comment that the vehicle has a rattle, tick, or knock type noise.
Some customers may also state that the MIL may have been illuminated.
– This noise and/or MIL light may also be accompanied by DTC P0300 (Engine Misfire
Detected) and/or a specific cylinder misfire DTC such as P0300, P0301-P0306 or
possible camshaft correlation codes P0016-P0019.
Note: Please take a sound file or video with sound of any noise prior to any disassembly.
If this step is skipped, you may be asked to reassemble the engine prior to being helped
with determining if the engine needs to be replaced. See the latest version of PIP5358 –
Vehicle Noise Diagnosis and TAC Requests for Assistance with Noise Related
Complaints for instruction on using the PICO for this.
This sound file may be needed when contacting GM Technical Assistance Center (TAC)
or if needed further review with engineering. This noise could be all the time, only under
load, or intermittent depending on the severity of the noise. You may find this noise hard
to isolate to one area in the engine. After you have recorded a sound file of the noise, try
to isolate the noise to a general area of the engine. At that point following the steps in this
bulletin in order may help pinpoint the concern.
The concern may be more noticeable on the Active Fuel management System (AFM)
cylinders.
Cause
This condition may be caused by spongy Stationary Hydraulic Lash Adjusters (SHLAs) or
damaged Switching Roller Finger Followers (SRFF), damaged camshaft actuator or
camshaft locating slots or a left bank timing chain tensioner gasket not sealing. The
condition could be all the time, only under load, intermittent, or when first started after a
hot soak depending on the cause.
Correction
If any of the conditions listed above have been verified, refer to the Service Procedure
below.
Service Procedure
1. Perform injector diagnosis to ensure there are no
leaking injectors causing a noise due to excessive
fuel in one cylinder:
• Perform GDS2 or AFIT test on injectors to
isolate a leaking injector.
• Replace any out of specification injectors.
• Re-evaluate the noise.
2. Perform cylinder cancellation for each cylinder.
This may help pinpoint the source of a rattle noise.
3. Perform normal SI diagnostics testing all spark and
fuel components for issues. Coil grounds and
wiring, injector concerns, spark plugs, etc.
4. Remove the intake manifold and visually inspect
for excessive carbon on the intake valve stems and
top of the valve causing noise.
• If carbon is present, then follow Service Bulletin
# 16-NA-383 to clean the valves or replace
heads as needed.
• Re-evaluate the noise concern.
5. Remove the cam cover of the affected bank or both
if unable to isolate to inspect for soft, spongy, or
damaged SHLAs or rockers on all cylinders.
5924232
⇒ Push down on the rocker end at the SHLA to
test for soft or spongy feel.
Bulletin No.: 21-NA-278
November, 2021
Page 3
7. Without starting the engine, crank engine over and
ensure that the valves are opening and closing.
– If they are not operating correctly, it will be
necessary to inspect the SRFFs for any damage.
8. Inspect the SRFFs and rocker assemblies for any
damage or dislodge.
⇒ While inspecting the rockers, it will be
necessary to rotate the engine over by hand to
ensure that the rockers are opening the valves.
Note: Camshaft carrier assembly removal will be
necessary to fully inspect the rockers and SRFFs.
⇒ Below are pictures of possible SRFF failures. If
any one of the SRFFs are damaged, it will be
necessary to replace all four on the affected
cylinder.
5924230
⇒ Check for any visible damage to non-AFM
rocker clips.
5924236
⇒ Broken Torsion Spring
5924231
Note: If all SHLAs (lifters) are hard and no damage to
rockers is visible, proceed to step 6.
6. If the replacement SHLAs are still spongy, it will be
necessary to remove the affected head and inspect
the head gasket for debris in the oil passages as
indicated in the graphic above.
⇒ If debris is found, inspect the camshaft caps for
wear or discoloration due to lack of oil.
⇒ If wear or discoloration is found, then replace
the cylinder head assembly with camshafts.
⇒ If there is no wear or discoloration, clean the oil
passages and replace the head gasket.
⇒ Change the oil and filter.
⇒ Reevaluate the noise concern.
5924237
⇒ Broken or Worn Pin Shelf
Page 4
November, 2021
Bulletin No.: 21-NA-278
9. Remove the camshaft actuators on the bank that is
misfiring and inspect the end of the camshafts and
the pin in the actuators for being bent.
⇒ If any broken parts are found during inspection,
replace all damaged parts.
5924233
⇒ Stuck Locking Pin
For any of the above conditions, engine
replacement is not necessary. Please perform
the repair for the particular issue found.
5924234
5924235
10. Inspect the left bank timing chain tensioner gasket
for not sealing correctly.
⇒ Replace the tensioner and gasket if this
condition is found.
11. If noise condition is still present, proceed to
step 12.
12. Raise the vehicle while running or with an assistant
inside.
• With chassis ears or a stethoscope, listen to the
right and left side of the engine.
• Once the noise is isolated or if unable to isolate,
remove the piston and rod assemblies from the
affected bank(s) to inspect for either a loose rod
bushing in the rod or a loose wrist pin in the
bushing.
• There should be no metal in the oil for this
condition.
• If this is found, a piston and rod assembly will
repair this noise.
Once all the above inspections and/or diagnostics are
completed, if nothing is found to be the cause for the
noise, engine replacement MAY be necessary.
Version
1
Modified
Released November 23, 2021
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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