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7 Critical Signs Your Knock Sensor is Failing (Complete Diagnosis Guide)
Apr 19, 2025
Discover everything you need to know about knock sensors in this comprehensive guide. Your engine's health depends on this critical component! In this in-depth video, we explore: ✅ What knock sensors actually do and how they protect your engine ✅ The 7 warning signs of a failing knock sensor you shouldn't ignore ✅ Step-by-step testing procedures anyone can follow ✅ Complete replacement walkthrough with torque specifications ✅ How to prevent expensive engine damage before it happens 👇 COMMENT BELOW: What engine sensor should we cover in our next video? #KnockSensor #EngineRepair #CarMaintenance #CheckEngineLight #AutoRepair #DIYMechanic #EngineDiagnostics
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0:00
that unusual pinging sound coming from
0:02
your engine isn't just annoying it's
0:04
potentially destructive hello automotive
0:06
enthusiasts today we're diving deep into
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one of the most critical yet overlooked
0:10
components in your vehicle the knock
0:12
sensor this tiny device serves as your
0:14
engine's personal guardian constantly
0:16
monitoring for destructive vibrations
0:18
that could lead to catastrophic damage
0:20
by the end of this video you'll
0:22
understand exactly what knock sensors do
0:24
how to identify when they're failing and
0:26
why addressing issues promptly can save
0:28
you thousands in repairs what is a knock
0:30
sensor let's start with the fundamentals
0:32
a knock sensor is a PZO electric sensing
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device strategically mounted on your
0:36
engine block or cylinder head its
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primary purpose is detecting vibrations
0:41
caused by engine knock also known as
0:43
detonation or pinging engine knock
0:45
occurs when the air fuel mixture in your
0:47
combustion chamber ignites before it
0:48
should instead of a controlled burn
0:50
initiated by your spark plug you get
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multiple flame fronts colliding inside
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the cylinder these collisions create
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pressure waves and vibrations that can
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seriously damage your engine components
1:00
the knock sensor works by converting
1:02
these mechanical vibrations into
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electrical signals think of it as a
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highly specialized microphone constantly
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listening to your engine's operation
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when it detects the characteristic
1:12
frequency of engine knock typically
1:13
between 5 to 8 kHz it immediately alerts
1:16
your engine control module ECM your ECM
1:19
then makes real-time adjustments to
1:21
protect your engine retarding ignition
1:23
timing delaying when the spark occurs
1:26
enriching the fuel mixture adding more
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fuel relative to air reducing boost
1:30
pressure in turbocharged engines these
1:32
adjustments continue until the knocking
1:34
stops effectively preventing damage to
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vital engine components like pistons
1:38
connecting rods and cylinder walls
1:39
location and types knock sensors
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typically come in two varieties resonant
1:43
knock sensors tuned to detect specific
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frequencies non-ressonant knock sensors
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capable of detecting a wider range of
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vibrations most modern vehicles use one
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to four knock sensors depending on the
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engine design they're commonly found on
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the engine block between cylinders on
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the cylinder head on the intake manifold
2:00
in V configuration engines you'll often
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find one sensor per cylinder bank inline
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engines typically use one or two sensors
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strategically placed to monitor all
2:09
cylinders symptoms of a failing knock
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sensor now let's examine the seven
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distinct symptoms that indicate your
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knock sensor is failing identifying
2:17
these early warning signs can prevent
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extensive engine damage one check engine
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light the most common and obvious
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indicator is your check engine light
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illuminating on your dashboard this
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happens because your ECM has detected
2:28
abnormal signals or no signals from your
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knock sensor when diagnosing this issue
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connect an OBD2 scanner to retrieve the
2:36
specific trouble codes the codes most
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commonly associated with knock sensor
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failures include P 0325 knock sensor
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circuit malfunction bank 1 P 0326 knock
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sensor range performance bank 1 P 0327
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knock sensor low input bank 1 P 0328
2:53
knock sensor high input bank 1 P 0329
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knock sensor input intermittent bank 1 P
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033 0 P 0334 similar codes for bank 2
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knock sensors remember these codes don't
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necessarily confirm a failed sensor they
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simply narrow down the area to
3:10
investigate wiring issues and ECM
3:12
problems can trigger the same codes two
3:14
decrease fuel economy when your knock
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sensor fails your ECM enters a
3:18
protective limp mode without accurate
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knock detection it defaults to
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conservative settings to prevent
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potential engine damage significantly
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retarding the ignition timing enriching
3:28
the fuel mixture beyond optimal levels
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these protective measures create
3:32
inefficiency you might notice 10 to 15%
3:35
reduction in fuel economy more frequent
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refueling stops higher fuel costs over
3:39
time i've seen vehicles lose up to 5 to
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7 MPG when running with a faulty knock
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sensor this inefficiency serves as both
3:47
a protection mechanism and a warning
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sign three reduced engine performance
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with your ECM in protective mode
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performance suffers considerably the
3:54
symptoms include sluggish acceleration
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particularly noticeable during highway
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merging reduced overall power output 15
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to 25% power loss in many cases higher
4:04
RPMs needed to achieve the same speed
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hesitation when pressing the accelerator
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rough idle especially when the engine is
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cold this performance drop isn't subtle
4:13
you'll feel like your vehicle has
4:14
suddenly aged several years the
4:16
decreased responsiveness feels similar
4:18
to driving with a partially clogged fuel
4:20
filter or dirty air intake four
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increased emissions the altered air fuel
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mixture and ignition timing lead to
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incomplete combustion this causes higher
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hydrocarbon HC emissions increased
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carbon monoxide CO outputs greater
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nitrogen oxide NOx production visible
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black smoke smoke in some cases failed
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emissions tests modern emissions testing
4:40
equipment can quickly detect these
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irregularities often resulting in failed
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smog checks or inspections five engine
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knocking or pinging sounds ironically a
4:48
failed knock sensor often leads to
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actual engine knock without the sensor
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to detect these damaging vibrations your
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ECM can't make the necessary adjustments
4:57
to prevent them listen for metallic
4:59
pinging or knocking sounds especially
5:01
under load sounds that increase with
5:03
engine rpm noise that's most noticeable
5:06
during acceleration prominent knocking
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when the engine is hot these sounds
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indicate that actual detonation is
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occurring a serious condition that can
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rapidly damage your engine's internal
5:15
components six error codes during
5:17
diagnostics beyond the check engine
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light specific diagnostic codes provide
5:21
valuable information p325 P334 codes
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directly relate to knock sensor circuits
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which 11171
5:29
P075 codes system 2 lean/rich often
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appear alongside knock sensor issues
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higher 300 PS308 misfire codes
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frequently accompany knock sensor
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failures when multiple related codes
5:43
appear together it strengthens the
5:44
diagnosis of knock sensor issues rather
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than isolated problems seven long-term
5:49
engine damage the most serious
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consequence of ignoring knock sensor
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failure is permanent engine damage
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continued detonation can cause piston
5:57
ring land fractures cylinder wall
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scoring connecting rod bearing damage
6:00
cracked piston crowns damaged valve
6:03
seats head gasket failures the repair
6:05
costs escalate dramatically at this
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point from a $501 150 sensor replacement
6:10
to potential engine rebuilds costing
6:12
$3,000 $5,000 i've personally seen cases
6:16
where ignoring knock sensor warnings led
6:18
to catastrophic engine failure within
6:20
just 500,000 to1,000 mi of aggressive
6:23
driving testing and diagnosis if you
6:25
suspect knock sensor issues here's how
6:27
to properly diagnose the problem visual
6:29
inspection first locate your knock
6:31
sensor and examine the sensor's physical
6:33
condition connection integrity look for
6:36
corrosion damage wiring harness for
6:38
chafing or exposed wires proper mounting
6:40
loose sensors give false readings
6:42
electrical testing for more definitive
6:44
diagnosis use a multimeter to check
6:46
resistance values most knock sensors
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should read between 100 and 200 kil at
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room temperature infinite resistance
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indicates an open circuit very low
6:56
resistance suggests a short for advanced
6:58
testing use an oscilloscope a
7:00
functioning sensor creates a distinctive
7:02
waveform when the engine block is tapped
7:04
flatline readings indicate a
7:05
non-responsive sensor computer
7:07
diagnostics connect an OBD2 scanner and
7:10
check for relevant trouble codes review
7:12
live data streams test sensor response
7:14
during engine operation replacement
7:16
process replacing a knock sensor
7:18
typically requires tools needed socket
7:20
set typically 78 or 22 mm for sensor
7:24
torque wrench penetrating oil for
7:26
stubborn sensors anti-seize compound for
7:28
installation step by step process locate
7:30
the sensor consult your vehicle's repair
7:32
manual disconnect the battery negative
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terminal unplug the sensor's electrical
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connector remove any components blocking
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access unscrew the sensor using the
7:40
appropriate socket compare the old and
7:42
new sensors for match apply a small
7:44
amount of anti-seas to threads but never
7:47
on the sensor tip install the new sensor
7:49
to manufacturer specifications torque to
7:52
proper specifications typically 1520 for
7:54
an infrared lbs reconnect electrical
7:56
connector and battery clear any engine
7:59
codes with scanner perform test drive to
8:01
verify resolution important
8:03
considerations always use OEM or
8:05
highquality aftermarket sensors never
8:07
apply sealants that could dampen
8:09
vibrations ensure proper torque to avoid
8:11
damage or false readings be careful not
8:14
to damage wiring during replacement
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prevention and maintenance to extend
8:17
knock sensor life and prevent related
8:19
issues use recommended fuel octane
8:21
rating keep ignition components in good
8:23
condition maintain proper engine
8:25
temperature dress check engine lights
8:27
promptly use quality fuels avoid ethanol
8:30
where possible change oil at recommended
8:32
intervals keep cooling system in optimal
8:34
condition understanding your knock
8:35
sensor is more than technical knowledge
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it's about protecting one of your most
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valuable investments this small
8:41
component plays an outsized role in your
8:43
engine's longevity and performance by
8:45
recognizing the warning signs we've
8:46
covered and taking prompt action you can
8:49
prevent minor issues from escalating
8:51
into major repairs remember that proper
8:53
diagnosis is essential the symptoms
8:55
we've discussed can sometimes indicate
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other problems so professional testing
8:59
is often worthwhile if you found this
9:01
information valuable please consider
9:03
subscribing to our channel for more
9:05
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9:07
comment below with any questions about
9:09
knock sensors or to suggest topics for
9:11
future videos until next time
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