Bulletin No.:

Service Bulletin

Date:

19-NA-219
September, 2019

INFORMATION
Subject:

Diagnostic Tip for Misfire, Chirp, Squeak, Squeal or Tick Noise, Malfunction Indicator
Lamp (MIL) Illuminated - DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307
and/or P0308 Set

Attention: This Bulletin only applies to vehicles equipped with V8 engines.
This Bulletin replaces PIP4138R. Please discard PIP4138R.

Brand:

Model:

Model Year:

VIN:

from

to

from

to

2002

2018

All

All

Engine:

Transmission:

V8

All

Buick
Cadillac
Chevrolet
GMC
HUMMER

GM
Passenger
Cars and
Trucks

Pontiac
Saab

Involved Region or Country

North America, Europe, Russia, Middle East, Iraq, Israel, Palestine, Argentina, Chile,
Colombia, Ecuador, Peru, Venezuela, Japan, Cadillac Korea, GM Korea, China, Taiwan,
Thailand, Singapore, Philippines, Africa

Condition

Some customers may comment on one or more of the following conditions:
• Misfire
• Chirp
• Squeak
• Squeal
• Tick
• MIL illuminated
Some technicians may find one or more of the following DTCs set in the Engine Control
Module (ECM):
• P0300: Engine Misfire Detected
• P0301: Cylinder 1 Misfire Detected
• P0302: Cylinder 2 Misfire Detected
• P0303: Cylinder 3 Misfire Detected
• P0304: Cylinder 4 Misfire Detected
• P0305: Cylinder 5 Misfire Detected
• P0306: Cylinder 6 Misfire Detected
• P0307: Cylinder 7 Misfire Detected
• P0308: Cylinder 8 Misfire Detected

Copyright 2019 General Motors LLC. All Rights Reserved.

Page 2

Information

September, 2019

Bulletin No.: 19-NA-219

Noises described coming from the engine may occur consistently or it may occur
intermittently:
– If a noise is verified, it will not be eliminated by canceling fuel injectors and the noise
will occur at camshaft speed (half of crankshaft speed).
– The noise may be described as a chirp, squeak, squeal or tick noise and may increase
off of idle.
– In either case, the cause of this concern may not be isolated after following
SI diagnosis.
This Bulletin is written for technicians who experience this concern and follow
SI diagnosis without isolating the cause of this concern.

Recommendation/Instructions
If SI diagnosis does not isolate the cause of this
concern, it may be the result of any of the following:
• Worn camshaft lobe and/or lifter roller
• A sticking valve
• Valve leakage
• A broken valve spring
• A collapsed AFM (Active Fuel Management) lifter
If SI diagnosis does not isolate the cause of this
concern, review the information below, determine which
description best matches the vehicle you are working
on, and perform the suggestions as necessary, starting
with the easiest ones first:

1. Worn Cam Lobe and/or Lifter Roller:
Generally, a worn cam lobe on this engine family will
create a consistent chirp, squeak, squeal or tick noise
at camshaft speed and/or a misfire with a P0300-P0308
DTC. The misfire may or may not be felt and the misfire
could occur at all RPM or just a specific RPM, such as
idle only or only at high RPM. If a noise is present, it will
not be eliminated by cancelling fuel injectors and
generally, the static compression and cylinder leakage
will be similar on all cylinders.
The following suggestions may help determine if a worn
cam lobe and/or lifter is causing this concern:
1. Use a wooden hammer handle to apply pressure to
the following locations of the rocker arms during
the noise to determine which one is making noise:
• Valve side
• Push rod side
• Side of the rocker
⇒ If the noise is changed by applying pressure to the
valve side of the rocker, this is most likely the result
of a lifter and/or cam lobe concern on that cylinder.
Sometimes this works, sometimes it does not - it
seems to depend on the amount of cam lobe wear.
2. Disconnect the coils and injectors on one bank of
the engine, run the engine with the related valve
cover removed, and back off the related rocker arm
a couple of turns and listen for a change in the
noise. If necessary, both rockers and push rods
can also be removed one cylinder at a time with
the related coil and injectors disconnected.
⇒ If the noise is eliminated and there is no
problem found with the valve spring, push rod,
or rocker arm, this is most likely the result of a
worn lifter roller and/or cam lobe.

3. Measure the cam lobe lift at the push rod side of
the rocker arm. The lift in this location will differ
from the SI specification but it should be similar as
compared with other rockers on the same bank.
The misfiring/ticking cylinder should obviously
have less lift than the comparison cylinders if this is
the result of a worn lifter roller and/or cam lobe.
Another possibility of no/low lift on cylinders 1, 4, 6,
or 7 on an AFM engine would be a collapsed AFM
lifter.
⇒ If a collapsed AFM lifter is found, refer to the
latest version of PIP4568 for additional
information.
Note: The step below will NOT work on 2017 and 2018
models.
4. On engines with AFM, you can command AFM on
with the scan tool, which will unlatch the lifters on
cylinders 1, 4, 6, and 7 and stop opening the
related valves.
• If the noise is eliminated, there is a good
chance that the noise is coming from the
valve-train of cylinders 1, 4, 6, or 7.
• If there is no problem found with the push rods,
rockers, or valve springs, the noise is most
likely coming from a worn lifter roller and/or cam
lobe on cylinders 1, 4, 6, or 7.
5. If the tests above do not isolate the cause of this
concern, it may be necessary to visually inspect
the lifter rollers and cam lobes for the following
conditions:
• Visual damage
• Flat spots
• Pits
• Grooves
• Scoring
• Gouging
• Flaking
• Rusting
⇒ It is very easy to overlook a damaged cam lobe
when inspecting them through the lifter bores
and just because the lifter rollers are not worn,
does not mean that the related cam lobes are
okay. Both pieces need to be carefully
inspected. It may help to use a bore scope or
pen light when inspecting the cam lobes
through the lifter bores. In some cases, the
worn cam lobe may not be discovered until the
camshaft is physically removed from the engine
and inspected for the issues mentioned above.

Bulletin No.: 19-NA-219

September, 2019

Notice: Follow SI procedures to replace the camshaft
and all lifters if a worn camshaft lobe or lifter roller is
found. Also replace the plastic lifter guide for the lifter
that had the damaged cam lobe and/or lifter roller (For
2010 Model Year, replace all the plastic lifter guides).
On AFM engines, also replace the VLOM (Valve Lifter
Oil Manifold) filter screen that is under the oil pressure
sensor.

Page 3

Typically, the Cylinder Leakage Test outlined in SI
should isolate valve leakage by finding excessive
leakage past an intake or exhaust valve, as compared
with others.
Notice: If a valve sealing concern is found, it should be
repaired by following SI repair procedures.

4. Broken Valve Spring:
2. Sticking Valve:
Generally, a sticking valve on this engine family will
cause an engine misfire that may or may not be felt and
it may occur consistently or intermittently. It is unlikely
that any engine noise will be present. It may be
temperature sensitive and it may be more apparent
during certain operating conditions, such as driving up
a grade, cresting a hill, or during hard acceleration. A
good indicator of a sticking valve is if engine misfires
continue to count on an aggressive deceleration with
engine braking. If the misfire occurs consistently, a
static compression test, running compression test or
cylinder leakage test may isolate the sticking valve.
However, it is unlikely that any of these tests will isolate
the sticking valve if the misfire only occurs while driving
at specific conditions.
The following suggestions may help determine if a
sticking valve is causing this concern:
Note: Follow SI procedures to remove the valve
springs and seals from the valves of the misfiring
cylinder. Before removing the air pressure from the
cylinder, tightly wrap a rubber band or tie strap around
the tip of each valve stem to prevent the valves from
dropping into the cylinder. Release the air pressure
from the cylinder and work the valve up and down in the
guide while turning the valve 360 degrees.
•

If any binding is felt, a stem to guide clearance
concern exists and should be repaired by
following SI procedures.
• If okay, rotate and snap the valve onto the valve
seat to make sure that it easily comes off of the
seat again. If you have to use force to tap the
valve off of the seat, excessive carbon build up
exists, which may be repaired by decarbonizing
the engine.
Notice: Refer to the latest version of Service Bulletin
16–NA-383 for decarbonizing instructions.

3. Valve Leakage:
Generally, valve leakage on this engine family will
cause a consistent engine misfire that may or may not
be felt and is more apparent at idle or low RPM.
Normally, no engine noise will be present and in most
cases, a static compression test or running
compression test will not reveal anything abnormal
unless the leakage is very high.

Generally, a broken valve spring on this engine family
will cause a tick noise and/or an engine misfire. In
either case, the concern may occur consistently or
intermittently. If it is causing an engine misfire, it may or
may not be felt and it may only occur at specific
operating conditions, such as high RPM driving, etc.
In some instances, a static compression test, running
compression test, and/or cylinder leakage test may
isolate the broken valve spring, while in other
instances; it may not if the spring remains stacked
together during the tests. As a result, it may be
necessary to visually inspect the valve springs by
closely examining them. Sometimes, the two broken
pieces of the spring will remain stacked together
making it hard to detect when visually inspecting them.
As a result, it may help to lightly push on different
places on the springs with a small hammer handle.
Notice: If a broken valve spring is found, replace the
broken valve spring as necessary.

5. Collapsed AFM Lifter (Engines with
AFM Only):
Some customers may comment on a MIL illuminated,
engine misfire, and/or tick noise. This may be the result
of an AFM lifter that unlocks as soon as the engine is
started or one that is mechanically collapsed/stuck.
• If an AFM lifter unlocks as soon as the engine is
started, a MIL and DTC P0300 will be experienced
with engine misfires on cylinder 1, 4, 6, or 7 but it
is unlikely that any noise will be experienced.
• If an AFM lifter is mechanically collapsed/stuck, a
consistent valve train tick noise, SES light, and
DTC P0300 will be experienced with engine
misfires on cylinder 1, 4, 6, or 7.
Notice: If either of these AFM lifter concerns is
suspected, please refer to the latest version of PIP4568
for additional information.
Notice: If there is an AFM lifter concern on RPOs L83,
L86, LT1 and LT4, follow the latest version of Service
Bulletin 15-06-01-002.

Page 4

September, 2019

Bulletin No.: 19-NA-219

Warranty Information
For vehicles repaired under warranty, please use the
appropriate warranty labor operation based on the
actual cause and repair.

Version

1

Modified

Released September 20, 2019

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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