What and How Do The Following sensors Work and What is their Functions? What is The effects on your vehicle if They are Bad?

MAP ( MAP-Barometric Pressure ) Sensor ?

Throttle Position sensor?

Manifold Automatic Tuning Sensor?

EGR ( Emission Gas re-Circulation) Valve?

PVC valve?

Idle Air Control valve?

Oxegyn sensor? ( O2 sensor)

If They are bad what do we expect to happen to The vehicle, and what other Computer controlled Functions are affected By it.

for instance IF The Map sensor is bad will it cause the Throttle position sensor to react improperly causing a hesitation on accelleration? Does it usually cause Flooding? very important Questions for The Low to no budgeted Income persons That have to follow The symptoms to The Most likely cause. Would The Map sensor or The TPS sensor cause The IAC Not to function correctly.

 

Any contamination can result in a lazy or inaccurate
sensor. Inaccurate sensor activity can result
from air leaks prior to the oxygen sensor or the
introduction of fuel via the carbon canister or
contaminated crankcase oil.
High O2 Sensor Readings: A high O2 sensor voltage
is an indication of a rich condition. Considerations
should include a rich carburetor or leaking fuel
injectors, excessive fuel pressure, inaccurate coolant
sensor reading, contaminated crankcase oil,
canister purge problems or a saturated canister,
faulty MAP sensor or low vacuum to the sensor.
Low O2 Sensor Readings: A low O2 sensor voltage
is an indication of a lean condition. Considerations
should include proper PCV operation, a grounded
oxygen sensor lead, fuel injector restriction, low
fuel pressure, grade of fuel, poor MAP sensor signal
input, exhaust leaks, vacuum leaks, improper operation
of the air management system and air leaks
prior to the oxygen sensor.
Fooled Sensor: The oxygen sensor can be fooled. A
misfire will introduce oxygen into the exhaust
manifold. The oxygen sensor will falsely interpret a
lean condition and signal the ECM to provide a fuel
enrichment.
MAP SENSOR
The MAP sensor incorporates a pressure sensitive
disc or diaphragm which converts manifold pressure
to a voltage signal or frequency. When it
comes to fuel authority, the MAP sensor is the boss.
It can starve the engine for fuel or wash the cylinders
down with a rich mixture.
Sensitive Sensors Can Send the Wrong Signals

Optimum engine performance, fuel economy
and low emission output is dependent upon
computers. Computers are dependent upon accurate
information provided by the sensors. A defective
sensor, lazy sensor, or a sensor out of range can
destroy the computer’s ability to maintain proper
control. This article will focus on some of the major
sensors and how they may affect the overall performance
of the system.
OXYGEN SENSORS
The oxygen sensor monitors the presence of oxygen
in the exhaust and provides the computer with
a voltage signal in relation to the amount of oxygen
present. The signal strength varies depending on
the amount of oxygen present in the exhaust manifold
in relation to outside oxygen. Based on the
strength of the signal voltage, the computer will
adjust the fuel mixture and provide proper fuel
control for optimum performance, lower emission
output and protection of the catalytic converter.
The oxygen sensor is a battery of a sort. It has the
capability of producing a voltage ranging from 0 to
1 volt. When discussing oxygen sensor voltages,
we normally refer to millivolts (mv). A normal
sensor voltage range would be in the 200 to 900 mv
range. The oxygen sensor must be at a minimum of
600°F to function. The voltage range can be monitored
with a high impedance (min. 10 megohm)
volt/ohm meter. Some sensors are of the heated
design, and the purpose of the heater is to improve
sensor activity and keep contaminates off the sensor,
which impede the accuracy of the sensor. Rich
fuel mixtures and oil additives can render the
sensor inoperative. Silica contamination from silicone
sealers, such as RTV, has been a problem, too.
tected through the aid of a lab scope or frequency
meter. Some test equipment may give inaccurate
readings when used on certain sensors, as they
average the signals or voltage pulses.
Fooled Sensor: Check for an exhaust system restriction;
a kinked, pinched, split, loose, or deteriorated
vacuum supply hose to the MAP sensor; or any
engine condition which may result in a low or
fluctuating vacuum signal.
COOLANT SENSORS
The coolant sensor is a very important player in the
computer control system. The coolant sensor signals
affect the fuel mixture, timing, idle speed,
cooling fans, evaporative purge control, the exhaust
gas recirculation (EGR) valve and the torque
converter clutch control (TCC).
The sensor can fail due to an open circuit, shorted
circuit or an out of range sensor. A sensor which is
out of its calibration range or defective can result in
poor driveability, surging, stalling, spark knock,
activation of cooling fans, an engine miss, or even
a no-start condition on TBI and PFI systems. A
condition of engine overheating or contamination
of the coolant can result in inaccurate sensor readings.
Check for loose connections, too.
CHECKS:
1) Coolant level: The proper coolant level
should be maintained as vapor pockets can
form around the coolant sensor, affecting the
sensor’s accuracy. The temperature of the
vapor is actually lower than the coolant,
which results in inaccurate readings.
2) Contamination: Cooling system deposits or
contaminates may restrict coolant flow or
deposit on the sensor, affecting the sensor’s
sensitivity. A 50/50 mix of anti-freeze and
water is the preferred mixture. This level
provides protection from temperature and
raises the boiling point of the coolant, reducing
the potential of vapor pockets forming.
3) Permanent Is Not Permanent: The frequency
of the recommended cooling system flush
signal in relation to engine load. It can be damaged
by shock or excessive pressure, or be fooled by too
little vacuum. Trouble codes may or may not be
stored in the computer’s diagnostic memory.
SYMPTOMS:
1) On engines equipped with port fuel injection,
a no-start will usually occur if the MAP
signal is lost.
2) If the voltage drops below 1 volt, the engine
will usually start up and stall out; sometimes
you can keep the engine running by patting
the accelerator pedal rapidly.
3) A sensor out of range (such as too low) may
result in a violent detonation, due to overadvanced
timing and a lean fuel mixture.
4) A defective sensor will result in a loss of
power and poor driveability.
5) A defective sensor or sensor out of range can
contribute to poor fuel economy, due to a
rich fuel mixture and retarded timing.
CHECKS:
1) Check for a vacuum restriction to the MAP
sensor; tee in a vacuum gauge and observe
the reading as you snap the throttle. The
gauge should drop to zero and recover immediately.
2) Check for tight vacuum hose connections.
3) Check for moisture in the vacuum hose to the
MAP sensor; the moisture can freeze and
restrict vacuum to the sensor. To eliminate
frozen restrictions, position the vacuum hose
above the engine so the vacuum hose is
routed downhill.
4) Check for vacuum hose cracks or collapsed
tubing.
5) Examine the electrical connector pins for
proper termination and any oxidation.
6) Check for vacuum leaks.
7) Check all circuit grounds.
8) Check for proper fuel pressure, as the MAP
sensor cannot compensate for low fuel pressure.
9) Check for unstable vacuum due to worn
engine parts.
Always rule out the obvious prior to replacing the
MAP sensor.
A failure in the sensor circuit will affect ignition
timing, the fuel mixture and emission output. A
trouble code should be set in the diagnostic memory.
Examine the integrity of the sensor’s connection
and the element which extends into the intake
plenum for carbon or other contaminates. Any
contamination will result in inaccurate readings. A
coated or contaminated sensor will signal the computer
that the air mass is colder than actual temperature,
resulting in a fuel enrichment and high
emission output. Replace any contaminated MAT
sensor.
EVP SENSOR
The EGR valve position (EVP) sensor is a linear
potentiometer which provides a voltage signal to
the ECM in relation to the EGR valve pintle movement.
The signal is a reference voltage which the
ECM uses to calculate the EGR flow rate. A defective
or worn EVP sensor will result in a rough idle
and stalling condition. The Check Engine light will
usually illuminate and a trouble code may be
stored in memory. The sensor should provide a
base voltage reading when the valve is in the closed
position and a steady voltage increase as the EGR
valve opens. The EVP sensor signal affects EGR
flow and ignition timing.
THROTTLE POSITION SENSOR (TPS)
The TPS sensor is a potentiometer which provides
a variable voltage signal to the ECM in relation to
the throttle position or angle. At closed throttle, the
voltage signal will usually be below 1 volt; at wide
open throttle, the voltage will be above 4 volts. The
voltage signal is used by the ECM to accurately
control the fuel mixture, spark timing, torque converter
clutch, emission control components and
the air conditioning (AC) clutch control circuit.
Coolant sensor
4) Check for air flow restrictions and proper
cooling fan operation, all of which can affect
the coolant sensor’s activity.
AIR CHARGE TEMP (ACT) SENSOR
The purpose of the ACT sensor is to monitor the
temperature of the air in the intake manifold and
provide a fuel enrichment in relation to a given
temperature. The air density affects the fuel mixture,
therefore, the air/fuel mixture must be adjusted
in relation to temperature. A temperature of
-40° F. could increase the pulse width of the
injectors as much as 30 degrees. At 40°F. the pulse
width could be increased 17 degrees, and so forth,
based on manifold temperature. At higher temperatures
(220°F) the sensor has no effect on fuel
authority. The ACT sensor might be considered as
an automatic choke of a sort.
A contaminated or inoperative ACT sensor can
affect cold engine performance, ignition timing,
injector pulse width, EGR and emission output.
Make certain you check the integrity of the pin
connectors and for broken or frayed wires.
MANIFOLD AIR TEMP (MAT) SENSOR
Some systems use a speed density means of computing
the air flow rate. On those systems, the
manifold pressure and manifold temperature are
used to calculate the airflow rate. The MAT sensor
may also be referred to as an intake Air Temp
Sensor (ATS). The sensor is a temperature sensitive
resistor which varies the voltage signal to the ECM
in relation to a given manifold air temperature. Air
density varies with temperature.
The sensor incorporates moving parts which are
susceptible to wear from friction, resulting in inaccurate
sensor signals. Cracked or worn spots on the
resistance substrate can result in inaccurate signals,
too. This can be monitored with a volt meter. While
performing a voltage sweep test, there should be a
steady increase in the signal strength from closed
throttle to wide open throttle. Any sudden change
in signal strength is a reflection of an open, cracked
or burned resistance substrate.
A sensor out of adjustment may affect the idle speed
or performance at part or full throttle; a sensor with
an open circuit would result in no fuel enrichment
on acceleration. A sensor that is defective or out of
adjustment will affect the fuel economy, put the
idle speed in a hunting mode, illuminate the Check
Engine light, cause a timing variation and other
performance deficiencies.
SUMMARY
Diagnosing a deficiency in a computerized system
can be a nightmare. A technician may be chasing
a problem which occurred for one millisecond,
yesterday. Before you dive too deep into the diagnostics,
go for the basics first. Always check the
power and ground circuits at the battery and computer.
Check the charging system output, as a high
or low voltage condition can affect the sensor’s
accuracy. Check the sensor’s activity via a scan
tool, volt/ohm meter, frequency meter or lab scope.

 

What a Wealth of Knowledge, awesome info on understanding how The computer translates info and where which info comes from. This I can follow easily and love the info Thanks

Question on air charge sensor, is it The one That plugs into The rubber part That attaches the air filter unit to the plenum ( air intake area? )

 

Yep, that's it. You can check it to see if it's working at all by putting a digital VOM on the connections, set you meter to measure OHMS, then blow on the sensor, the readings should change..if they don't, it's bad.