00:00 - 00:03
So today, we're explaining
all the car engine sensors
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Every single one of them.
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And for each of them, we're going to explain:
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What it does.
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How it works.
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Where the sensor is located.
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And what happens if it goes faulty.
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Obviously, this is a pretty long video, with
information on 16 different sensor types.
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So, of course, you can find timestamps
for each sensor down in the description.
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So that you can quickly access only
the sensors you're interested in.
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Now, although there's a lot of
sensors that are needed for the engine
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and the ECU(or the engine control unit)
to do their job properly.
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Many of them work in pretty similar ways.
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They do different things, but they
have very similar characteristics.
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And this is why to make things more
logical and easier to understand I
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have grouped sensors into five categories.
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Temperature.
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And air-fuel ratios, emissions and others.
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And we're starting right
away with position sensors.
00:57 - 01:01
The crankshaft position sensor tells
the ECU the position of the crankshaft.
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Because the position of the piston is fixed
in relation to the position of the crankshaft.
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By knowing the position of the crankshaft, the ECU
also knows where the piston is inside the bore.
01:12 - 01:18
And by knowing this, it can initiate fuel injection
and/or spark ignition events, at the correct time.
01:18 - 01:22
Crankshaft position sensors are most often
either Hall effect, which is three wires.
01:22 - 01:25
Or VR(variable reluctance) which is two wires.
01:25 - 01:30
Although they work slightly differently, both
rely on the basic principles of electromagnetism,
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to read a trigger wheel made from a ferrous metal.
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The trigger wheel is going to
have one or more teeth missing.
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And whenever a missing tooth
passes in front of the sensor,
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it's going to change the signal
that the sensor sends to the ECU.
01:44 - 01:47
Now, the position of the missing
tooth in relation to the sensor,
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is going to be fixed to a certain
position of the crankshaft.
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And by seeing the change in
the signal, the ECU can tell
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exactly where the crank is at that moment in time.
01:58 - 02:02
Now the ECU is also configured to the
total number of teeth on the trigger wheel.
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And by knowing the total number of
teeth, and measuring how often the
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missing tooth passes in front of the sensor,
the ECU can calculate engine speed or RPM.
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Now, every car engine has one crankshaft, and thus
it only needs one crankshaft position sensor.
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The crankshaft position sensor in order to read
the trigger wheel must be located very near it.
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And the trigger wheel must be
installed on something that rotates
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at the same speed as a crankshaft.
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And it's usually either the crankshaft pulley,
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the timing gear where the timing belt or
timing chain attaches, or the flywheel.
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So, one of these three locations is where you're
going to find your crankshaft position sensor.
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If the sensor fails completely,
then the engine will not start.
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Or it will start but stall
after running very briefly.
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If the failure is not complete, then you
may get jerky or uneven acceleration,
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engine misfiring, rough running,
poor idle, bad mileage, and so on.
02:54 - 02:58
Now, the camshaft position sensor does the
same thing as the crankshaft position sensor.
02:58 - 02:59
But for the camshaft.
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Now, in theory the engine can run with a crank sensor alone.
03:03 - 03:08
But adding a camshaft position sensor paints
a much more complete picture for the ECU.
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And it's also a layer of verification for the
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information coming from the crankshaft position sensor.
03:13 - 03:16
Now, a camshaft position sensor lets the ECU know,
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what each cylinder is doing and when is it doing it.
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And this is why it can be used for,
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for example, cylinder selected
knock control, sequential injection.
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And other cylinder selective systems.
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The cam sensor works on the same
principle as the crank sensor.
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The only difference is, that it reads a
much smaller trigger wheel with fewer teeth,
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due to the size of the camshaft.
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To read the position of the camshaft,
the cam position sensor must be near it.
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Usually, you're going to find
it somewhere on the cam cover.
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Either at the front or at
the back of the camshaft.
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Or less often somewhere along
the axis of the camshaft.
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Failure symptoms are usually the same
or very similar to a position sensor.
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Either a no-start condition,
or poor engine running.
03:58 - 04:02
The throttle position sensor measures
the position of the throttle plate.
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When you're operating the throttle
pedal, you're actually operating
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the throttle plate that's usually at
the entrance of the intake manifold.
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When you floor it, the throttle plate gets fully
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opened, allowing maximum air into the
engine, for maximum acceleration.
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By knowing the position of the throttle plate,
the ECU can know the load placed on the engine.
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And can thus vary injection and ignition timing accordingly.
04:24 - 04:28
A throttle position sensor works
by relying on a variable resistor.
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A variable resistor is essentially
an electrical component,
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which changes its electrical resistance
output based on its position.
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It contains a movable part.
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And different positions of this movable
part will have different resistance output.
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In case of the throttle position sensor,
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the throttle plate shaft is connected
directly to the variable resistor.
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So different positions of the throttle plate
will have different resistance outputs.
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Which are then measured and converted
into a useful signal for the ECU,
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by the onboard electronics of
the throttle position sensors.
04:57 - 05:01
Now, this is what old throttle
position sensors used to work with.
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modern throttle position sensors, actually
rely on non-contact position measurements.
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And either use Hall effect, induction or magnetic resistance
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to do the same job as a variable resistor.
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Obviously, to measure the
position of the throttle plate,
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the throttle position sensor must be
located on the throttle body itself.
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And this is where you always
the throttle position sensor.
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One of the most obvious symptoms of
a failed throttle position sensor,
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is going to be unpredictable acceleration.
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The car is going to feel as though it's not
correctly responding to throttle pedal inputs.
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Also the idle will often be affected.
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And it will either be too high or too low
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And there also might be
difficulty starting the vehicle.
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In addition to knowing the position
of the piston, so that it can know
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when to inject the fuel, the ECU must
also know how much fuel to inject.
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And to know how much fuel to inject, it must
know how much air is coming into the engine,
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so that it can inject a
corresponding amount of fuel.
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And this is exactly what a MAF(or mass
air flow) sensor does for the ECU.
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It tells the ECU how much air
is coming into the engine.
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Now, most MAF sensors are
either hot wire or hot film.
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Now, they are bit different
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And the hot film sensor is a bit more advanced.
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But they both rely on the same basic
principle, of the very high temperature
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coefficient of resistance of certain
metals, such as platinum or tungsten.
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The very high temperature coefficient of
resistance of these metals, means that even
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very minute changes in the temperature of
these metals, will change their resistance.
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So when air flows over these metals,
it changes their temperature.
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The more air flows over, the
more the resistance changes.
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And the onboard electronics of
the MAF sensor measure this,
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and then convert the signal
into useful data for the ECU.
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Now, obviously this is just
a basic working principle.
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And a MAF sensor is more complicated
and more interesting than this.
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But I do have a video that goes into
great detail when it comes to MAF sensors.
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And you can find it in the description below, and
in the suggested videos in the top right corner.
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You will usually find a MAF right after the
air cleaner housing, the air filter housing.
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If it's not there, it's going to be
somewhere after the air filter housing,
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but before the throttle body.
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If a MAF fails completely,
the engine will not start.
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If it's only starting to fail, or
if it's a bit contaminated by dirt,
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then it's going to send the
wrong information to the ECU.
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So the ECU will be injecting
the wrong amount of fuel.
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And you can expect a rough running engine.
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A poor idle, hesitation during acceleration,
the engine stumbling, poor mileage.
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And other similar symptoms.
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Now, an AFM, or airflow meter,
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or vane airflow meter as it's also
known, does the same thing as a MAF.
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It measures how much air
is coming into the engine.
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It just does it differently, and it's
usually present on older vehicles.
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The airflow meter has a flap or a vane inside it.
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And the incoming air pushes against this flap.
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The more air is coming in, the more it
will push against and open the flap.
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Now, the vane or flap is
connected to a variable resistor,
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just like the throttle blade shaft
of the throttle position sensor.
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Different vane positions are going to output the resistances.
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And then the onboard electronics are going to measure this,
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and convert it into a useful signal for the ECU.
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So the different resistance outputs
will tell the ECU how much the vane is open,
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and how much air is coming into the engine.
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Just like the MAF sensor,
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the airflow meter is always going to be
somewhere near or right after the air filter.
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Since it's doing pretty much the
same thing as a mass airflow sensor,
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the failure symptoms of an airflow
meter are going to be similar
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or the same as with a mass airflow sensor.
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Just like the MAF or the AFM, the
MAP(manifold absolute pressure) sensor
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measures how much air is coming into the engine.
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But unlike the AFM or the MAF , it does
not measure the incoming air mass directly.
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Instead, it measures pressure
inside the engine's intake manifold,
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and calculates the air mass based on that.
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The logic is that the more air
there is in an encode space,
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the greater the pressure that air is going
to exert onto the walls of that cold space.
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And this is exactly what the MAP is using
And by measuring the pressure,
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it can calculate how much air is coming into the engine.
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The MAP sensor measures intake air pressure, by
relying on a tiny micromachined silicon chip.
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The silicone chip consists of a silicon
membrane, and a tiny piezoelectric material.
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The piezoelectric material reacts to
the flexing of the silicon membrane,
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under pressure, by changing its electrical charge.
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The more the pressure there is,
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the more the silicon membrane flexes,
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the more the charge changes.
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And the onboard electronics measure this, and
then convert it into a useful signal for the ECU.
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Now, if you're building a performance engine
or significantly increasing the boost levels
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of your engine, then the stock MAP sensor will no
longer be adequate and will need to be upgraded.
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Now, AEM carries a whole range
of robust, reliable, and accurate
10:07 - 10:09
MAP sensors to suit all needs.
10:09 - 10:11
If you need them, check'em out below
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Because the MAP must measure
pressure directly in the intake
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manifold, it's also always located
somewhere on the intake manifold.
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And again, because it's ultimately
trying to measure the incoming air mass,
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failure symptoms are going to be similar
or the same as with a MAF or AFM.
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The oil pressure sensor obviously
measures oil pressure inside the engine.
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It's a very simple, but perhaps one of the most
important and vital sensors for the engine.
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Because without enough oil pressure, the engine is
going to sustain catastrophic damage very quickly
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Just like many other pressure sensors on a car,
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the oil pressure sensor is basically
a piezoresistive pressure transducer.
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Meaning that it works on pretty much the same
basic principle as the MAP sensor we just covered.
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It's simply calibrated for the different
values expected from the engine's oil pressure.
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Now in some cases, the oil pressure sensor
of an engine is not a sensor at all.
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It's just a switch.
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And the most basic version contains a diaphragm.
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Which when it flexes, it simply causes
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an electric circuit, and reports that
there is sufficient oil pressure.
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If there isn't enough oil pressure, the
diaphragm isn't going to flex enough.
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It won't be able to cause the electric circuit.
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And an oil pressure light is going
to illuminate, warning the driver
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that the engine should be
shut down to prevent damage.
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The oil pressure sensor is usually
located somewhere on the engine block,
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often near the oil filter.
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But it can be anywhere on the engine
block, where it can be tapped directly
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into an engine oil passage, so that it
can accurately read the oil pressure.
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A lack of oil pressure is one of the single
most dangerous situations for an engine.
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So if the oil pressure sensor is malfunctioning
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and falsely reporting whole
oil pressure to the ECU,
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then the ECU will falsely
trigger a limp home mode,
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or will refuse to start the engine.
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Obviously, the fuel pressure
sensor measures fuel pressure.
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That's what it does.
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So why is it important to measure fuel pressure?
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Well by knowing the fuel pressure
of the fuel inside the fuel rail,
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the ECU can know how long to open the injectors,
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in order to ensure that the correct amount
of fuel is injected into the engine.
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In order to measure fuel pressure
right inside the fuel rail,
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the fuel pressure sensor is almost always
located somewhere directly on the fuel rail.
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Usually, the first symptom of
failure is difficulty starting.
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Especially on a cold engine.
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Other symptoms include poor
acceleration and poor mileage.
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Now the IAT sensor
(or the intake air temperature sensor)
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Obviously measures the
temperature of the intake air.
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Now, it's important to do this, because air
density is influenced by air temperature.
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The hotter the air, the
less dense it's going to be,
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and the less molecules of air
are going to be in a given space.
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Although in theory, an engine could
run without an air intake sensor,
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it's still a very good idea to have one.
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And the engine's going to run
better with it, than without it.
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The IAT sensor works together
with the MAF, MAP, or AFM
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to give the ECU a more complete picture
of the air coming into the engine.
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Which helps reduce emissions and
improve power and efficiency.
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Just like almost all the other temperature
sensors in a car, the IAT sensor is a thermister.
13:15 - 13:17
Meaning that its electrical
resistance is going to change,
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in response to the changes in its temperature.
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And then as usual, the resistance is measured
and converted into a useful signal for the ECU.
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The IAT sensor is often integrated
into the MAF or the AFM.
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If it's not there, you can usually
find it somewhere in the intake duct.
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Usually near the throttle body.
13:34 - 13:36
If you're building a performance or racing engine,
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and you need to add an intake
air temperature sensor,
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then AEM has the right one for you.
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It's easy to install
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And it's reliable and accurate.
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As always, links are down below.
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If there's only a bit of dirt on the IAT sensor,
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then malfunction symptoms are going
to be very mild and barely noticeable.
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If the fault is more severe, then the engine
may run rough, stumble, or even stall.
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Or it can have very mild, short surges of power.
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All the remaining temperature sensors
we're going to cover are also thermisters,
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so we won't be individually
explaining how each one of them works.
14:05 - 14:08
We'll just talk but they do
where they are and so on.
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So let's proceed with the
coolant temperature sensor.
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Now, the coolant temperature sensor
is very important for the ECU
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Because it tells it how warm the engine is.
14:16 - 14:18
This is important because a cold engine
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needs a different amount of fuel,
when compared to a hot engine.
14:21 - 14:24
The coolant temperature sensor is also
needed to trigger various actions.
14:24 - 14:26
Such as for example starting the radiator fans
14:26 - 14:31
Or if the engine is overheating, it can
tell the ECU to trigger limp home mode.
14:31 - 14:34
Or refuse to start the engine,
until it cools back down.
14:34 - 14:35
Like almost all the other temperature sensors,
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the coolant temp sensor must
come into direct contact
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with the fluid whose temperature
it's trying to measure.
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As such we are very often going to find the
coolant temp sensor at or near the thermostat.
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Some cars have more than one, and you can
find them anywhere on the coolant piping,
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or wherever else coolant is passing through.
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A cold engine needs more fuel than a hot engine.
14:53 - 14:56
This means that if the coolant
temperature sensor is malfunctioning,
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and telling the ECU that the engine
is cold, even though it's hot.
14:59 - 15:03
The ECU is going to inject extra fuel, which
is going to result in a rich running condition.
15:03 - 15:05
And this means you're going to get poor mileage,
15:05 - 15:08
or even black smoke from
the exhaust in severe cases.
15:08 - 15:12
An opposite scenario is also possible, and
the ECU can think that the engine is hot,
15:12 - 15:13
even though it's cold.
15:13 - 15:16
In that case, it's going
to inject too little fuel.
15:16 - 15:18
Which is going to lead to
a lean running condition.
15:18 - 15:22
And this can lead to the engine misfiring,
or even knocking, until it heats up.
15:22 - 15:26
Fuel temperature must be measured because
fuel density, just like the density of air,
15:26 - 15:28
is affected by temperature.
15:28 - 15:31
Hot fuel is less dense and burns more easily,
15:31 - 15:34
so a bit more of it must be
injected to compensate for this.
15:34 - 15:38
The fuel temperature sensor is most
often located somewhere at the fuel tank.
15:38 - 15:41
Often as part of the fuel pump assembly.
15:41 - 15:44
Less often it can be found
somewhere else along the fuel lines.
15:44 - 15:47
The information coming from the fuel
temperature sensor is only used to
15:47 - 15:51
further improve the injection accuracy, in
order to meet stringent emission standards.
15:51 - 15:54
An engine can run pretty well with
a faulty fuel temperature sensor,
15:54 - 15:58
and in some cases symptoms
might not be noticeable at all.
15:58 - 16:01
If the fault is more severe or
if the sensor component fails,
16:01 - 16:03
then the vehicle might fail in emissions test.
16:03 - 16:06
Or get slightly worse mileage
and performance than usual.
16:06 - 16:10
Automatic cars only have an oil pressure
sensor, and do not measure oil temperature
16:10 - 16:14
Measuring oil temperature can be a
useful additional layer of protection.
16:14 - 16:18
If the oil overheats, this is going
to negatively impact its viscosity,
16:18 - 16:23
and the oil won't be capable of doing its
job, which can lead to engine failure.
16:23 - 16:27
Now the ECU, by seeing the oil temperature,
can activate the limp home mode,
16:27 - 16:31
or refuse to start the engine, before
oil temperature normalize again.
16:31 - 16:35
In addition to relaying information to
the ECU, the oil temperature sensor can
16:35 - 16:38
also relay information to engage,
or display visible to the driver.
16:38 - 16:41
And then the driver can take preemptive action,
16:41 - 16:44
and shut the engine down if
oil temperatures get too high.
16:44 - 16:46
In order to be able to measure the temperatures of
16:46 - 16:50
oil, the sensor must come into direct
contact with the oil inside the engine.
16:50 - 16:54
As such it's often found on the engine
block, or less often on the cylinder head.
16:54 - 16:58
In newer cars, it can be found
integrated into the oil level sensor.
16:58 - 17:01
Depending on how it fails, a
malfunctioning oil temperature
17:01 - 17:04
sensor might make the ECU think that
the oil temperatures are too high.
17:04 - 17:05
Even though they aren't.
17:05 - 17:08
And then the ECU might incorrectly
trigger a limp home mode.
17:08 - 17:13
The sensor can also malfunction in a way that
it fails to report overly high oil temperatures,
17:13 - 17:15
which can result in engine damage.
17:15 - 17:20
A faulty oil temperature sensor is very easy
to spot, if there's a gauge or display for it.
17:24 - 17:28
The O2 or the oxygen sensor measures the
amount of oxygen present in the exhaust gases.
17:28 - 17:31
The amount of oxygen present in exhaust gases,
17:31 - 17:36
directly corresponds to the amount of
fuel burned inside the combustion chamber.
17:36 - 17:39
By measuring the oxygen, the oxygen
sensor can actually tell the ECU
17:39 - 17:42
the air-fuel ratio at which the engine is running.
17:42 - 17:47
Now, the air-fuel ratio, or the ratio of
air to fuel inside the combustion chamber,
17:47 - 17:51
is absolutely critical for both
engine performance and emissions.
17:51 - 17:55
And must be constantly monitored to
ensure that it is where it needs to be.
17:55 - 17:57
We have two kinds of oxygen sensors.
17:57 - 17:59
Narrowband and wideband.
17:59 - 18:03
Narrowband sensors can tell if the
engine is running rich or lean.
18:03 - 18:09
But they cannot tell exactly, how rich
or how lean the engine is running.
18:09 - 18:14
On the other hand, the wide band sensor
covers a much wider range of air-fuel ratios.
18:14 - 18:19
And you can tell the ECU exactly how
rich or lean the engine is running.
18:19 - 18:22
Although it's small, the oxygen
sensor is a pretty complicated device.
18:22 - 18:26
It involves zirconium bulbs, and
various platings and what not.
18:26 - 18:30
And explaining it in this video would really
make the video too long and complicated.
18:30 - 18:34
So, for the purposes of this video what I
will tell you, is that the amount of oxygen
18:34 - 18:39
measured at the sensor tip, corresponds
to a voltage produced by the sensor.
18:39 - 18:44
So for example, 0.5 volts is going
to be near the ideal air-fuel ratios.
18:44 - 18:48
And at the other far ends of the spectrum,
we can find too rich and too lean.
18:48 - 18:52
So what the ECU is going to do, it's going
to increase or decrease the amount of fuel
18:52 - 18:57
injected, in order to reach again
the ideal air-fuel targeted ratio.
18:57 - 19:02
Now, most catalytic converter equipped cars, are
going to have a minimum of two oxygen sensors.
19:02 - 19:05
One is going to be before, and
one after the catalytic converter.
19:05 - 19:08
The one before the catalytic converter
is called the upstream oxygen sensor,
19:08 - 19:12
and it's usually going to be right at
the exhaust manifold, or right behind it.
19:12 - 19:17
And it's used to see the exact air-fuel
ratio at which the engine is running.
19:17 - 19:21
The one after the catalytic converter, that
sensor is called the downstream sensor.
19:21 - 19:26
And it's used to verify that the catalytic
converter is properly doing its job.
19:26 - 19:29
Failure symptoms can range from
barely noticeable, to very noticeable.
19:29 - 19:35
But even if the symptoms are hard to notice, the
vehicle is likely going to fail an emissions test.
19:35 - 19:38
Now, if it's noticeable, it's
going to be really noticeable.
19:38 - 19:39
The engine is going to run rough
19:39 - 19:43
Especially on more modern cars, which
rely more heavily on the oxygen sensor.
19:43 - 19:49
More modern cars, can even refuse to start the
engine if the sensor has completely failed.
19:49 - 19:53
If you know that you have a bad oxygen
sensor, then it's a really good idea
19:53 - 19:57
to replace it as soon as possible,
even if the vehicle is running okay.
19:57 - 20:01
Because an overly rich running condition,
can lead to your catalytic converter
20:01 - 20:03
failing far more sooner than it needs to.
20:04 - 20:08
Now, wide-band oxygen sensors are
also an absolutely critical tool
20:08 - 20:10
for tuning performance and racing engines.
20:10 - 20:14
And the AEM carries one of the most
popular, and the fastest responding,
20:14 - 20:16
wideband setup on the market.
20:16 - 20:18
Links are below.
20:18 - 20:21
An EGT is an exhaust gas temperature sensor.
20:21 - 20:25
And as the name reveals, it measures
the temperature of the exhaust gas.
20:25 - 20:29
Now, an EGT is a probe that must be
present directly in the exhaust stream,
20:29 - 20:32
in order to measure the
temperature of the exhaust gas.
20:32 - 20:37
By measuring the temperature of the exhaust, we
can infer information about the air-fuel ratio.
20:37 - 20:42
Because changes in the air-fuel ratio,
are also going to be directly correlated
20:42 - 20:44
with changes in the exhaust gas temperature.
20:44 - 20:47
Now, an EGT probe isn't often
used on gasoline engines.
20:47 - 20:52
But it can be useful to protect the turbo, and
the catalytic converter from thermal overall.
20:52 - 20:56
Now, EGT probes are often used on
turbo diesel and diesel engines
20:56 - 21:00
to verify that the DPF(or diesel particular filter) has reached a
21:00 - 21:02
sufficiently high temperature for regeneration.
21:02 - 21:07
They're also useful for protecting the
SCR(or selective catalyst reduction)
21:07 - 21:12
in LNT(or lean NOx trap)
and other NOx absorbing systems.
21:12 - 21:16
Although it's considered an old tool when it
comes to tuning performance and racing engines,
21:16 - 21:20
an EGT probe can still be a very
useful tool that provides valuable
21:20 - 21:22
insight into what's happening inside the engine.
21:22 - 21:27
Naturally, AEM has some very sleek
EGT setups, that you can check out.
21:27 - 21:30
In order to get the most accurate
reading of exhaust gas temperatures,
21:30 - 21:33
the EGT probe must be as close to
the exhaust valves as possible.
21:33 - 21:38
This is why you're always going to find it in the
exhaust manifold very close to the cylinder head.
21:38 - 21:40
The other location is always going to be after
21:40 - 21:44
the DPF, or diesel particular filter,
to verify if the DPF is doing its job.
21:44 - 21:48
EGT probes
are very rarely present from the factory gasoline engines,
21:48 - 21:52
so really aren't any very
common symptoms to discuss.
21:52 - 21:53
When it comes to diesel vehicles.
21:54 - 21:59
An EGT failure is going to cause the vehicle
to go into regeneration mode very often.
21:59 - 22:02
And regeneration mode is going
to last longer than usual.
22:02 - 22:05
And you may also get poor
mileage and poor performance.
22:05 - 22:07
Now, NOx are nitrogen oxide sensors.
22:07 - 22:10
And they measure the amount of
nitrogen oxides in the exhaust gases.
22:10 - 22:13
They're usually only present on diesel vehicles,
22:13 - 22:17
and were briefly present on some stratified
charged gasoline engines in the past.
22:17 - 22:21
Their main role is to verify the
correct operation of the SCR.
22:21 - 22:23
Or the selective catalyst reduction system.
22:23 - 22:26
This is an active emission
system in diesel vehicles,
22:26 - 22:31
which injects ammonia or diesel emissions
fluid, directly into the exhaust gases.
22:31 - 22:37
And this converts the nitrogen oxides into
nitrogen, water and minute amounts of CO2.
22:37 - 22:40
There's usually two of these
sensors in a diesel vehicle
22:40 - 22:43
One before, and one after the
selective catalyst reduction system.
22:43 - 22:47
The one before, measures how
much much nitrogen is coming in.
22:47 - 22:50
And the one after measures how
much nitrogen oxide is coming out,
22:50 - 22:54
to make sure that the selective catalyst
reduction system is doing its job.
22:54 - 22:58
A failure is going to trigger most modern
diesel vehicles to go into a "limp mode home".
22:58 - 23:01
You also might get an erratic
idle, and poor mileage.
23:01 - 23:04
Now 'knock' is abnormal
combustion inside the engine.
23:04 - 23:10
If it's strong enough, and if it persists long
enough, it can cause catastrophic engine damage.
23:10 - 23:13
A knock sensor is essentially a microphone.
23:13 - 23:17
Tuned to listen to the specific
frequency of knock inside the engine.
23:17 - 23:18
This depends on the engine,
23:18 - 23:22
but largely it actually depends on
the bore and stroke of that engine.
23:22 - 23:27
If the knock sensor detects knock, it's
going to relay this information to the ECU.
23:27 - 23:31
And the ECU is going to respond, by
either retarding ignition timing,
23:31 - 23:33
or increasing the amount of
fuel injected into the engine.
23:33 - 23:36
To prevent the knock from occurring again.
23:36 - 23:40
In order to be capable of hearing the knock
resonating throughout the engine block,
23:40 - 23:43
the knock sensor is always
going to be on the engine block.
23:43 - 23:49
Many engines with six or more cylinders have
two or even knock sensors in some cases.
23:49 - 23:53
In many cases, a knock sensor's failure will have
zero effect on the way the engine is running.
23:53 - 23:57
You might get a check engine light, but
the engine will run completely normal.
23:57 - 24:02
Now, the scenario is a bit different on more
modern cars, whose ECU once it detects knock
24:02 - 24:09
sensor failure, is going to often trigger a limp
home mode, until the knock sensor is replaced.
25:52 - 25:54
And there you have it.
25:54 - 25:55
All the sensors.
25:55 - 25:56
Is it really all the sensors?
25:56 - 25:57
Well, likely not
25:57 - 26:01
Because the number of sensors on
modern engines is growing everyday.
26:01 - 26:05
And by the time I was shooting this video,
somebody might have invented something new.
26:05 - 26:07
So if I did miss a sensor, let me know.
26:07 - 26:09
Also, if you want a more in-depth video
26:09 - 26:12
on any of the sensors in this
video, tell me about that as well.
26:13 - 26:14
So yeah, that's pretty much it for today.
26:14 - 26:16
As always thanks a lot for watching.
26:16 - 26:19
And I'll be seeing you soon,
with more fun and useful stuff.
26:19 - 26:21
On the D4A channel.