23-NA-115

Bulletin No.:
Service Bulletin
Date:
23-NA-115
March, 2024
TECHNICAL
Subject:
Ticking, Tapping or Snapping Noise from Engine - 5.5L RPO LT6 Realign Camshaft
Caps as Required
This Service Bulletin replaces PIP5920. Please discard PIP5920.
Brand:
Model:
Chevrolet
Corvette
Model Year:
VIN:
from
to
from
to
2023
2024
—
—
Engine:
Transmission:
5.5L
(RPO LT6)
—
Involved Region or Country
North America
Condition
Some customers may comment on a ticking, tapping, or snapping noise from the engine.
Note: It is important to note that this engine incorporates a mechanical valve train design
to enable maximum engine performance and does not use traditional hydraulic lifters and
as a result there will be some mechanical tick noise from the valvetrain, which is normal.
However, if the noise is excessive and not periodic, as described in this bulletin, this
procedure can be used to reduce the noise. For reference, this ticking disturbance noise
can be heard while the engine is idling and more noticeable with the hatch open and in
tour mode. It may also be found that the noise slightly increases as the engine gets
towards operating temperature.
Cause
This condition may be caused by the misalignment of the camshaft caps.
The verify you have this concern, it will be necessary to follow the steps below. Do not
proceed with this bulletin if the customer has not commented about this concern.
Important: Please read entire bulletin prior to performing any repair.
Correction
Copyright 2024 General Motors LLC. All Rights Reserved.
Important: You MUST use the PicoScope to verify if you have this noise concern.
Failure to use the PicoScope may result in incorrect diagnosis and the need for further or
unnecessary repairs.
Important: You need to take PicoScope measurements before and after the repair to
share with customer. Before performing any repair on the left or right side of the engine
please review the realignment procedure with the customer and ask them if they want to
proceed with the repair.
Important: Not all engines will see the same level of noise reduction after performing the
realignment procedure. Some engines may see a marginal improvement in noise
reduction.
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March, 2024
Bulletin No.: 23-NA-115
Important: Service agents must comply with all
International, Federal, State, Provincial, and/or
Local laws applicable to the activities it performs
under this bulletin, including but not limited to
handling, deploying, preparing, classifying,
packaging, marking, labeling, and shipping
dangerous goods. In the event of a conflict between
the procedures set forth in this bulletin and the
laws that apply to your dealership, you must follow
those applicable laws.
Service Procedure
Step 1:
Follow the directions below to setup the PicoScope to
obtain the sound file needed for review.
If you need to download or update the PicoScope,
follow the steps below:
1. Log into GM GlobalConnect.
2. Click on the "Departments" drop down menu and
select "Service.”
3. Under "Applications" on the service page, select
"Special Tools and Software updates.” (in Canada,
"GM Special Tools & Equipment - Software
Updates")
4. You will now be re-directed to
www.gmtoolsandequipment.com (do not access
this site directly as it requires the use of
GlobalConnect to allow downloads).
5. Click the link under "Software Downloads" for the
latest PicoScope software version and a new page
will open.
6374688
6. Click the setup links and follow instructions to
update the tool.
Step 2:
⇒ Start up the vehicle/engine. Ensure engine is at
operating temperature. Stand on the driver's side
and then passenger side of the engine to listen to
the suspected tick. Subjectively determine which
bank (LH vs RH) has a more prominent tick and
proceed with instrumenting on that bank.
Determine which side of the engine the noise is
coming from.
Bulletin No.: 23-NA-115
March, 2024
Page 3
Step 3:
Place the accelerometer on the suspect bank.
6374742
⇒ With the suspect bank determined, prep/position
the accelerometer so the X, Y, Z coordinate system
(that’s laser etched) is facing upwards before
securing to the bolt head. After accelerometer is
placed on bolt head, double check to ensure its
centered and did not rotate on the bolt head. Doing
so will ensure the best results.
Note: Ensure to keep the cable routed away from the
exhaust if working in the engine compartment or
moving parts if working under the vehicle.
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March, 2024
Bulletin No.: 23-NA-115
6374737
Important: Ensure accelerometer coordinates are
facing up towards the intake.
Step 4:
Hook up the accelerometer to the oscilloscope.
⇒ Screw the accelerometer connector into the sensor
interface. The red LED will start to blink when it
senses the connection. Attach a blue, red, and
green BNC cable to X, Y, and Z ports, respectively.
Then attach the blue, red, and green cables to
channels A, B, and C, respectively.
Bulletin No.: 23-NA-115
March, 2024
Page 5
Step 5:
Setup the software to collect data.
1. Open the GM NVH software and click on the NVH
button.
6374911
2. Start a new test with the setup wizard:
⇒ 1) Under RPM Signal – Ensure Static RPM is
set to 800 RPM.
⇒ 2) Under Vibration Signal – Select three-axis
mode then ensure all 3 channels are checked
and the location is set to Engine Compartment.
⇒ 3) Under Signal Options – Set the Maximum
Signal History Size to 500 seconds.
3. Go to the setup screen to finalize the wizard setup.
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March, 2024
Bulletin No.: 23-NA-115
6374914
4. Go to options at the top then to advanced options
and change the maximum frequency of interest to
2000. Update the SPL Weighting to dB(A) and
check that the accelerometer units are (m/s^2).
Under the FFT tab, change the responsiveness
marker to the position shown above. Finally, under
the filter tab, add a bandpass filter from 1300 to
2000 Hz.
Note: If the instrumentation needs to be moved, restart
the data collection.
4. After finishing the recording, click file then save.
Click OK on the details box as this input is optional
and save as a .pddata. Change the file name to
“[last 8 of vin]_[LH or RH bank]_[pre or post service
fix]_[date].”
Step 6:
Step 7:
Collect data.
1. Startup the vehicle/engine, leave at idle. Make
sure the HVAC is off and the vehicle is put into
weather mode so that the vehicle idles at 800 rpm.
Let the engine settle and wait for the suspected
tick to start.
2. When the suspected tick starts, click on the “start
recording” button. Let the recording go for 60
seconds, then click “stop recording.” Do not adjust
the accelerometer throughout the recording.
Analyze the data.
1. Right click in the time domain display and change
the display mode to single.
2. If scales on the left end for each channel are not
ranging from -4 m/s^2 to 4 m/s^2, right click in the
time domain display and select “reset scale.”
3. Pull the yellow window cursors on the bottom in as
close together as they will go.
4. Look at the channel lines in the time domain
window for ticks with a .15s gap between them.
⇒ Compare to the examples below for an engine
with a tick and an engine without a tick:
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Examples of Tick:
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Bulletin No.: 23-NA-115
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Bulletin No.: 23-NA-115
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Bulletin No.: 23-NA-115
Examples of No Tick:
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6375036
Important: Once you have captured your Pico results
before and after performing the service procedure,
please reset the settings menu to default for the next
user by clicking on the reset buttons at the bottom of
the advance PICO set up screens.
Once it is determined which bank the noise is coming
from, it will be necessary to follow the service
procedure below to adjust the camshaft cap torque.
Important: If the noise is heard from the left bank, the
camshaft cap adjustment procedure can be done with
powertrain in vehicle. If the noise is heard coming from
the right bank, it will be necessary to drop the engine
and transmission assembly to gain access and remove
the camshaft cover for the adjustment procedure.
Important: Please review the PICO results with the
customer and give them the option if they want their
powertrain removed and reinstalled for repair on the
passenger side.
Important: Ensure you batteries in the interface
module are good.
Camshaft Cap Re-Alignment Procedure:
Important: During the camshaft cap adjustment
procedure, you may notice a dull area on the camshaft
lobes. This is considered normal and does not require
any further service.
Please use the following procedure to execute a
complete bank camshaft re-alignment procedure:
1. If the tick noise is on the Driver’s side bank 1, the
repair can be done in the vehicle. If the tick is on
the passenger side bank 2, the rear cradle and
powertrain assembly must be lowered to be able to
remove the camshaft cover on that bank.
– Refer to Camshaft Cover Replacement – Bank 1
or Camshaft Cover Replacement – Bank 2 in SI
to get the camshaft cover removed to perform the
next steps.
2. Remove the camshaft cover (w/solenoids installed
in cover if LH bank, remove solenoids from cover
first if RH bank).
3. With aid of helper, rotate the engine from below by
the crankshaft damper bolt until the Intake Cyl #1
(LH) or Intake Cyl #2 (RH) cam lobes are pointed
straight up to the top of the cap (on base circle).
– This is the first cam cap that will be adjusted per
the steps 4-8 below.
– Note that the larger front camshaft caps behind
the actuators will NOT be adjusted with this
procedure.
Important: Always remember to work from front to rear
when performing the re-alignment procedure.
Page 12
March, 2024
Note: For the Bank 1 adjustment procedure, the cam
lobes can be monitored through the wheel well opening
to properly position.
Important: Note orientation of camshaft cap and bolts
in order to reassemble back into their original position.
Only remove one camshaft cap at a time.
4. Loosen and remove the camshaft cap bolts and
camshaft cap.
– Ensure there is still a film of oil on the camshaft
journal and underside of the camshaft cap, add
fresh oil to the surfaces if needed.
– Install camshaft cap to head and finger tighten
each bolt.
Important: Do not use excessive amounts of oil on the
surfaces – extra oil could run into the threaded bolt
holes leading to bolts being overloaded and possibly
breaking when tightened to the torque specification.
5. Tighten the inner camshaft cap bolt first to 15
N.m (11 lb ft).
Note: The inner camshaft cap bolt is the one closest to
the spark plug tube.
6. Tighten the outer camshaft cap bolt next to 15
N.m (11 lb ft).
Note: The outer camshaft cap bolt is the one farthest
away from the spark plug tube.
7. Make a second pass on both camshaft cap bolts to
confirm each is torqued to 15 N.m (11 lb ft).
8. Place a black sharpie mark on the cam cap
adjusted to note that it has been completed.
Important: During each camshaft cap adjustment
step, ensure the camshaft lobes are at base circle.
9. Move to the next valve position working from front
to rear on the intake camshaft. Rotate the engine
until the lobes are pointing straight up to the top of
Bulletin No.: 23-NA-115
the cap for that next position. Repeat steps 4-8 on
that position. Repeat this step for the rest of the
valve positions on that cam working front to rear.
10. Repeat the steps 4-8 above on the exhaust
camshaft caps on the same engine bank (LH, RH)
depending on the side on which you are
working on.
Important: Always remember to work from front to rear
when performing the re-alignment procedure.
11. Reinstall the cam cover and solenoids (if removed)
and reconnect electrical.
12. Once the exhaust and intake camshaft cap bolts
have been re-torqued, the engine can be
reassembled.
Important: If the work was done with the engine still in
vehicle (LH bank) and the cam phasing solenoids were
left installed in the cam cover, it is critical to make sure
that the solenoid plungers are fully recessed before
lowering the cover onto the engine. The plungers can
loosely move inward and outward. Tip the cam cover
front (solenoids) end down to make sure plungers are
in/down. Carefully move cover with the front (solenoid)
end tilted slightly down while positioning onto the
engine to prevent plungers from extending. If the
solenoid plungers are extended out, they will catch on
the phaser OCV center bolt plunger and be bent –
phasing will not work and both the solenoid and OCV
will need to be replaced.
Parts Information
Note: Only select the parts that coincide with the repair
performed. Replace the part with the P/N outlined in the
Electronic Parts Catalog (EPC) in accordance with the
vehicle VIN.
Causal Part
Description
Part Number
Qty
Bank
N/A
SEAL, OIL TRFER
TUBE O-RING
12697070
1
Right Bank
N/A
SEAL, OIL TRFER
TUBE O-RING
12697071
1
Right Bank
N/A
GASKET, EXH MANIF
12673594
1
Both Banks
N/A
GASKET, INT MANIF
12668302
8
Both Banks
N/A
BOLT, R/AXL SHF
11601876
12
Right Bank
N/A
FILTER KIT, OIL
12730579
1
Both Banks
N/A
OIL, ENG (5W-50)
SUPERCAR MOBIL 1
19433208 (in Canada,
19434897)
8
Both Banks
N/A
SEALANT
19369831 (U.S)
19369832 (Canada)
1
Both Banks
N/A
SEAL, CM/SHF
HSG CVR
12672530 Right
1
Right Bank
N/A
SEAL, CM/SHF
HSG CVR
12672531 Left
1
Left Bank
N/A
SEAL, SPLG SHLD
12672529
4
Both Banks
N/A
GASKET,
CTLTC CONV
10354707
1
Both Banks
Bulletin No.: 23-NA-115
March, 2024
Page 13
Causal Part
Description
Part Number
Qty
Bank
N/A
GASKET,
CTLTC CONV
12672379
1
Both Banks
N/A
GASKET, PCV
OIL SEP
12695546
1
Left Bank
N/A
SEAL, SPLG SHLD
12672529
1
Left Bank
N/A
BOLT, EXH MANIF
11546600
5
Both Banks
Warranty Information
Note: Only select the Labor Operation that coincides
with the repair performed.
For vehicles repaired under the Powertrain coverage,
use the following labor operation. Reference the
Applicable Warranties section of Investigate Vehicle
History (IVH) for coverage information.
Labor
Operation
Description
Labor Time
4089038*
Record and Review
Sound File
0.5 hr
4089048*
Camshaft Cap Realignment
Bank 1 (Driver’s Side)
Coupe
9.9 hrs
4089058*
Camshaft Cap Realignment
Bank 2 (Passenger Side)
Coupe
17.3 hrs
4089068*
Camshaft Cap Realignment
Bank 1 (Driver’s Side)
Convertible
6.6 hrs
4089078*
Camshaft Cap Realignment
Bank 2 (Passenger Side)
Convertible
16.6 hrs
*This is a unique Labor Operation for bulletin use only.
Version
5
Modified
Released June 28, 2023
Revised August 16, 2023 – Added an Important statement at beginning of Camshaft Cap
Re-Alignment Procedure and after Step 8 and clarified step 9.
Revised November 21, 2023 – Added the 2024 Model Year and updated steps 6 and 9 of
the Camshaft Cap Re-Alignment Procedure.
Revised March 05, 2024 – Updated Step 4 under Camshaft Cap Re-Alignment
Procedure.
Revised March 15, 2024 – Updated Important statement and Step 4 under Camshaft Cap
Re-Alignment Procedure to clarify removing the Bolts and Caps.
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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