Computer system fundamentals

Oxygen sensor

(02) these sensor measure the amount of oxygen in the engine exhaust gases before and after the catalytic converter, most newer sensor contain heaters and are refferd to as heated oxygen sensors (ho2s).

Truth tables

Chart that show what the output of a gate will be with different inputs, truth table for an or gate, if two switches are wired in parallel, either switch A or switch B (or gate) will turn the light on (output 1), the output will be on (1)with A or B or both energized, only when neither input is on will the output be off (0), truth table graphically shows how a gate functions.

Computer

Complex set of electronic circuits, and automotive computer will produce programmed electrical control current for actuators after receive specific input signals from sensors, computer now monitor and control all major systems of a modern vehicles. in the apst , automotive systems (ignition, cooling, emissions and fuel they used to worked independent, now on board computer networks work together at lightning fats speeds to react to almost anything condition, making the passenger vehicle a much safer, efficiency and powerful means of transportation.

Waveform

Computer signals can be measured with an oscilloscope scope or a scanned tool with a scope function, of a scope is connected to a sensor that generates a signal voltage, a trace of the signal, can be viewed on the scope, the're many type of electrical waveforms within the analog digital categories. AC some wave, Dc some wave, Dc square wave, Dc ramp wave, Pulse wave, Complex some wave, Voice wave, Dc noise wave.

Computer memory operation

Gates that are capable of storing data as voltage charges, the integrated circuits inside the memory chips will hold the data (on or off charges) until it is needed by the microprocessor.

Computer clock

Integrated circuit that use a constant pulse rate to coordinate when or how quickly signals are entitled throughout the complex circuits.

Not gate

Inverted or gate is a not gate, note the small circle that represent an inverter, the output is inverted to produce an output opposite that of an or gate.

Computer housing

Metal or plastic enclosure that protect electronic component from unwanted induced currents, moisture and physical damage.

Inverter and gate

Nand gate, it's output will be opposite that of an and gate, note the small circle or dot on the output lead of the gate, the small circle represents an inverter.

Switching sensor

Open or closed the sensor circuits to rpovide an electrical signals for the computer, transmission pressure switches are ex, of this type of sensor, a switching sensor can detect almost any condition and produces a digital signal (either on or off).

Circuit board

Plastic or fiberboard insulator with flat metal conductors printed on its surface to connect and hold components, a computer harness connector is a multi pin terminal that attaches to the vehicle wiring harness.

Super powerful brain computer

Process the inputs from the nervous system and determine what actions should be taken, ex, imagine you accidently pole a sharp needle into your finger, the result is chemical electrical signals for pain and a reaction signal to pull the needle away from your finger, first, your brain would almost instantly tell you, my finger is being injured, your brain would then take corrective action to protect your finger.like computer produce logical outputs, cells in the brain can be chemically electrically charges on or not be charged off, complex logical memory circuits, the brain can be decide what to do in almost any situation.

Output

The computer produces electrical outputs that are used to control solenoids, servo motors, relays and other actuators, these actuators, these actuators perform physical actions to alter component operation for maximum vehicle efficiency.

Duty cycle

The percentage of on time compared to total cycle time, along with pulse width, it can be used to measure a signal or pulse as a percentage, ex, if a solenoid is sent a 50% duty cycle, it will be turned on half the time and off half the time.

Impact sensor

these sensor detect a collision to shut off the fuel pump and engine, a similar type of impact sensor is used to deploy the air bag system.

Engine coolant temperature sensor

(ECT) this sensor measures the temperature of engine coolant, in most case , it is simply refferd to as a coolant temperature sensor.

Electrically erasable programmable read only memory

(EEPROM) electrically erasable programmable read only memory can be altered by the technicians in the field, this allow the manufacturer to easily change operating parameters of a performance or driveable problem is discovered.

Gate circuits

Electronic circuit that produce a specific output voltage for given input voltages, just as a diode will pass current when forward biased (output lead would have voltage representing one) and stored current when reverse biased (output would be zero or no voltage) Gates have programmed (previous knowing) output, the most common computer Gates are.

Voice wave

Irregular wave that corresponds to the frequency of the human voice airwaves, a microphone produces a weak analog wave propotional to the airwaves hitting the microphone.

Output drivers

It sometimes refers to as squad drivers or power transistors, control current flow through the actuators, when energized by the computer, the driver ground the actuator circuits, the actuator can then produce movement, such as turning the electric cooling fans.

Hall effect sensor

Sensor used a special semiconductor chip to sense part movement and speed, it produces a digital signal, these sensor are used as crankshaft and camshaft position sensor as well as pick up devices in some electronic ignition distion distributors.

Manifold absolute pressure sensor

(MAP), this sensor measure intake manifold vacuum in relation to a reference pressure (ususally a vacuum).

Programmable read only memory

(PROM) programmable read only memory contains permanent data that is more specific than the data store in rom, the microprocessor can read from the prom but it cannot write to the prom, a laptop computer with factory software is required to reset prom chip the prom contains specific information about the vehicles engine (number of cylinder, valve sizes, compression ratio, fuel system types) transaxle (shift, points, gears ratios, etc), weight, tire size, optional accessories and any unique features, there are three types of prom used in late model vehicle: eprom, eeprom, kam.

Random access memory

(RAM) random access memory is a memory chip use by the computer to store information or data temporarily this data is erased if battery power to the computer is removed.

Read only memory

(ROM) Read only memory stores permanent data that cannot be removed from memory, this memory chips contains calibration tables and lock up tables for the general make and model car.

Barometric pressure sensor

(baro), this type of sensor mesassure the outside air pressure around the engine. it a combined with the map sensor on most newer vehicle.

Camshaft sensor

(cs) this sensor measures camshaft position, rotation and speed so the computer knows the stroke of the engine (intake compression, power or exhaust).

Engine speed sensor

(ess) this sensor measures engine speed, it is often located next to a trigger wheel on the engine crankshaft snout, in older vehicles, it is located inside the distributor.

Flash erasable programmable read only memory

(feprom) flash erasable programmable read only memory is similar to eeprom in all respects, from is simply another name for an eeprom. Ecms used on late model vehicle used modified flash proms (high speed programmable read only memory) that is permanently fixed to the circuit board but can be erased and reprogrammed quickly with a laptop, older vehicle the Prom Chris is removable during computer replacement, the chip can be removed from the old computer and reused in the new computer, data is retain in the prom even when the chip is removed from the cpomputer.

Fuel pressure sensor

(fps) a modern fuel pressure sensor threads into the fuel rail to monitor the amount of gasoline pressure available at the inlet of the fuel injectors, some measure fuel pressure over time and can detect a leaking or clogged injector automatially.

Knock sensor

(ks) a knock sensor I usually a piezoelectric sensor thatdetect engines pinging pre-ignition or detonation so the ECM can retarded ignition timing or reduce turbocharger boost pressure.

Mass airflow sensor

(maf) thousands sensor sometimes measures the amount of intake airflowing into the engine, it is often refferd to as an airflow sensor or an airflow meter.

Throttle position sensor

(tps) this sensor measures the opening angle of the throttle valves to detect how much power is request by the driver.

Pulse wave

A pulse wave is a signal that rises progressively from zero and then almost instantly returns to zero.

DC ramp wave

A wave that moves steadily up from zero and the switches off almost instantly is a DC ramp wave.

Sensor classifications

An automobile used several types of sensors to provide electrical data to it's many computers, there are dozens of specific names for vehicle sensors, however they can all be classified into two general categories: active sensor and passive sensor.

Modern vehicles computer system

Compensate for mechanical wear or go out calibration, thinks very quickly, alternator outputs in milliseconds as computer alternator output almost instantly as inputs and operating conditions change, reduce fuel consumption and lower emissions by precisely consumption and lower emissions by precisely metering fuel into the engine, computer sensor circuits ''sniffs'' the exhaust gases to find out if too much or too little fuel is entering the engine, increase engine power by accurately controlling ignition timing, fuel injection, emissions control system operation, etc, reduce vehicle weight because they are much lighter than mechanical control mechanisms.

Conditioners

Converters or interfaces alter signals for used by other chips and circuits in the computer, an input conditioner alters the input from some sensors, if filters incoming data (voltage and current changes) ex, many sensor signals are analog, the conditioner can convert an analog signals into a comparable digital, square wave signals that the computer can understant, an output conditioner is needed to change digital signals back into analog signal for use by power transistor energize actuator or other computer.

Voltage regulator

Converts battery and generator voltage into lower, cleaner DC voltage that can be safely used by the ECM circuits, dash displays and sensors.

AC since wave

This wave is a cutting signal that smoothly fluctuates above and below zero volts, the electricity in your home or inside and alternator would produce an alternating current (ac) since wave at 120 v.

Reference voltage dc

around 5volts, the computer steps down battery voltage so that a smooth, constant supply of DC voltage is fed to the passives sensor, the sensor alters the reference voltage by changing it's internal resistance, this change in reference voltage is interpreted by the computer as a change in condition or state.

Circuit sensing

involves using the computer itself instead of dedicated sensors to monitor component and circuits operation, the computer monitor current flow through various components and circuiyts.ex, some circuit sensing system can monitor fuel injection operation (injector coil winding current) ignition coil action (current through ignition coil windings) and computer operation (current through computer circuits), the windings and the wires in the circuits serve as the sensors.

Keep alive memory and adaptive strategy

it found on some computer, kamm allows the computer to have an adaptive sstrategy , it needed as parts wear and components deteriorate, the information stored in kam allows the computer to maintains normal vehicle performance with abnormal inputs from sensor. it gives the computer the ability to also ignore false inputs to maintains good driveable.

Or gate

it'll produce an output (one or on) if either input is energized (1), A or B input voltage (1) will result in voltage (1) at the output lead.

Computer locations

it's located under the dash on the passenger side of the vehicle, this protect the delicates circuits and components in the computer from the engine heat, vibration, and moisture, high temperature electric drive train controller, can also located in the engine compartment, in the trunk or under the seat. it closer to most sensor and actuatyors, less wiring and fewer connectors are needed tied the system together. computer sued to operate the antu;lock brakes and other system are often found anywhere in the vehicle, engine and power train control module are located under the dash, in the engine compartment or Central location, computer used with specific system, the ignition or a/c systems,

And gate

it's require voltages (1) at both input to produces a voltages (1) at the output, of pin A and B are both (1) the output will be 1, if only pin Aor pin B is one, the output will be 0.

potentiometer

it's sensor changes it's internal resistance with a change in a condition, it's ohms value may change with temperature, pressureetc. its an analog sensor, it's variation of a variable resistor sensor, it has three external connections instead of two, one lead connects to each end of the resistor, and the remaining lead connects to a wiping arm that slides over the fixed resistor, this arrangement more precisely controls the current throughout than a two connection variable resistance sensor.

Digital signals

on/off signals, like those produces by a rapidly flipping switch, voltage output goes from maximum to minimum, a digital signals basically produce a square wave, ex, sensor providing a digital signal is a hall effect type crankshaft position sensor, which show engine room using a 12v signal, compare crankshaft and camshaft signals.

Binary numbering system

only two numbers, zero and one, and is the key to how computer operate, the number zero and one can be arranged in different sequence to represent other, numbers, letters, words, a computer input, a computer output or a condition, computers turns switches (transistor) either on or off, off would represent a zero and on would represent one in the binary system, 001 in binarywould equal a thhree in the base 10 decimal system, 0110 in binary would equal a six in the base 10 system.

Oil level sensor

this sensor measure the amount of oil in the engine oil pan.

Battery temperature sensor

this type of sensor monitor battery temperature so the computer can adjust vehicle operation to affect charging system output as needed.

Vehicle control module

Large, powerful computer processes data from sensors and other, less powerful control units, it coordinates engines, transmission, traction control and antilock brake function and instrumentation.

Inverter gate

Not gate will reverse it's input, if the input has voltage applied (1) the output terminals will not have voltages (0) or vice verse, a not gate can be used to make other gates.

Modern vehicle computer

On board diagnostic that can detect and record system problems, the on board computer can produce and store and output code that tells the technician where a fault might be located, increase driver convenience by better control of the passenger compartment environment and dash displays. improve passenger safety by controlling the antilock brakes, air bags, suspension and other system, compensate for component wear and faillure to keep the car driveable.

Active sensor and shielded wire

Produces it own voltage signal internally, this very weak signal is fed back to the computer for analysis, shielded wire, which has a flexible metal tube around the conductor to block induced voltage and interference, is often used with active sensors.

Signal amplitude

Refer to how much voltage is present in the wave, a high amplitude signal would have more voltage than a low amplitude signal, most automotive computer system use a signal amplitude of about 3-5 v.

Cybernetics

Refer to the study of how electrical mechanical devices can duplicate the action of the human body, comparing the human body to a computer system is an easy way to explain this subject, just as your brain communicate with and control parts of your body , an automotive computer system can communicate with and control parts of a vehicle.

Pulse width

Signal frequency, generally refers to how fast a voltage signal changes over time, the signal frequency from a sensor might be measure in milliseconds or thousandths of a second. high frequency signal would be very short (narrow) or have a short a short pulse width, a low frequency signal would be longer (wider) or would have a long pulse width.

Computer system block diagram

Simple service manual drawing that shows how the sensors, the actuator and the computer interact, it used basic squares or rectangles to represent component and lines to represent wires, computer block diagram is Handy when trying to find out what types of sensors are used and what conditions are controlled by a specific computer system.

Computer amplifier

Simply strenght a various signals inside the computer, an amplifier might increase the voltage signal from the oxygen sensor, which is less than one volt, then the signal is strong enough to be used by circuits in the computer.

Microprocessor operation

Small (micro) computer (processor), a microprocessor is an integrated circuit capable of analyzing data and calculating appropriate outputs, it brain of a computer, use binary number system to make decision, comparisons or calculation, digital pulse from the conditioners are fed into the microprocessor, since these inputs are off (0) or on (1) voltage, they can be used by the logic Gates in the processor, a microprocessor also use data stored in the computers memory, it compares input signals to memory data to decide what the output should be for maximum efficiency.

Reference voltage

Sometime abbreviate vref, is the base voltage used to carry a computer signal, the computer send a reference voltage to a passive sensor so a signal can be fed back for processing, a reference voltage is needed so a change in sensor resistance can be ready by the computer as a change in current and voltage.

Buffer

Device that can serve as temporary storage area for data, it can also protect internal computer chips from improper data, ex, if data is fed into the computer too quickly, the buffer can hold the data and then feed it into the other device at a controlled rate, in many cases the buffer is built into the input conditioners. computer memory stores data for the microprocessor. trouble codes and vehicle operating data are stores in memory.

Integrated circuit

Electronic circuit that has been reduced in size and etched in the surface of a tiny semiconductor chip, metal conductors on the top of the chip connect these various electronic components to form the circuit, wire leads allow for input and output connections to and from the IC chip, technicians often have to reprogram the integrated circuit in a vehicle computer to rectify problems.

Fuel tank pressure sensor

FTPS, this sensor measures the pressure or vacuum inside the closed evaporative monitoring system, it is similar in construction and operation to a map sensor, if someone leaves the gas cap off the vehicle, the system will detect a pressure leakage to inform the driver with a trouble code.

Digital electronics

Field of study dealing with the ways a computer used on-off signals to produce artificial intelligence, a computer analyzes input signals from sensors, it has memory in which fixed and semifixed data is stored, using small integrated circuits (ic) the computer can make logical choices on how to control specific output by comparing the input signals from sensors to known signals.

Automobile computer

Terminal refferd to any electronic circuits configuration that can use multiple inputs to find preprogrammed outputs, Central processing unit, Electronic control unit, Electronic control module, Engine control module, Electronic control assembly. Power train control module, vehicle control module, Microprocessor, logic module. when ready service manuals, to prevent confusion, control module when refferd to automotive computer in general.

DC Square wave

This digital, on-off signal stays at or above zero volts, the computer converts DC sine wave from sensors into DC square waves for logic chips inside the computer.

Complex sine wave

This signal voltage moves up and down erratically but gradually

Vehicle speed sensor

This type of sensor measures the vehicles road speed so the ECM can adjust fuel, ignition, transmission, suspension and other system operations, it is located in the transmission/transaxle housing or as part of the electric drive train.

DC noise wave

Traight line 9dc) with some voltage fluctuations (noise) noise is usually unwanted voltage spikes in a circuit and is caused by induced voltage from an outside source.

Vehicle sensors

Transduce , change a physical condition into an electrical signal, means to change from one form to another, just as our eyes, ears, nose, fingers, etc. can sense condition, vehicle sensors can detect the operating condition of a car or truck, the computers use the voltage signals from sensors to control the actuators, many mounted on the engine, on or in the transmission or transaxle, in the exhaust system, on the wheel hubs, on and in the fuel tank, on the suspension or even in the trunk (impact sensor).

Magnetic sensor

Use part movement and induced current to produces a signal for the computer, this type of sensor is commonly used to monitor speed (vehicle speed sensor) or part rotation, it usually produces an analog signal, magnetic sensor are also refferd to as permanent magnet (pm) generators.

Microprocessor

Usually the largest integrated circuit in a computer, the Microprocessor analyzes data from sensors and compares it to known good operating values in memory, memory chips store digital data, the Microprocessor chip can then produce decision or calculations for the proper output for actuator (fuel injector pulse width, ignition timing, throttle valve position and other function).

Passive sensor

Variable resistance sensor, voltage is fed to the sensor from the computer, the passive sensors resistance varies with changes in a condition (temperature, pressure, motion, etc..) the computer can detect the resulting changes in voltage caused by the change in resistance, within these two categories, are several sensor types.

Input

Vehicle sensors convert a condition into an electrical signal that can be use by the computer.

Computer signal

Voltage variation I've r short periods of time, it's and specific arrangement of pulses or waves used to carry electronic data or information, you must be familiar with computer signals to understand the operation and service computer system, it can be digital (square or on/off scope waveform) or analog (smooth, gradual change in current and voltage).

Binary language

Zero or a one is called a bit, a pattern of four boys is a nibble, a pattern of right boys is called a byte (pronounced bite) one or more Bute are refferd to as a word, you're more likely to hear this terminology when you work with home or personal computer.

Actuator

it's the hands and arms of a computer system, they allow computers to do work and alter the operation of the components and system. the actuator locations can be found anywhere on a vehicle, they can be located on the engine, in gtye doors or dash, under the hood and in the trunk, check and appropriate service manual for exact actuator locations. actuator classification used several types of output devices or actuator to control part operation, all actuator can grouped in the following categories, solenoid, relay, servo motor, display devices, control module.

Processing and storage

the computer compares sensor inputs the data and operating parameter in it's memory to determine what action should be taken to control the vehicle control circuits, the computer can remember programming, as well as store trouble codes in it's memory chips.

Computer mounted sensor

these sensor are tiny sensor wireinside a vehicle computer, yaw sensor, direction ensor, interior temperature sensor and other can be located inside the computer itself.

Hybrid drive circuit sensor

these sensor monitor HV battery temperature, generator output, HV battery charge, power control module output, motor generator torque/speed and other conditions.

Wheel speed sensors

these sensors measures wheel rotational speed for anti-lock brake, traction control and hybrid drive systems. Oput drivers are power transistors that step up current by providing a group path to operate actuator (fuel injectors, solenoids, servo motors and other high current devices).

Logic devices

they're making logical decisions (output) based on specific inputs (facts), if an and gate was compared with two switches wires in series, both switches (a and b) must be on to astivate the starter motor, compare these circuits to the action of the gates and the truth tables. logical gate can be connected together to form supercomplex circuits, millions of Gates can be interconnected to produce thousands of preprogrammed outputs (decision) from numerous inputs (facts), this is how a computer works, or thiinks,m it's circuitry and software are designed to make the correct output signals base on various input signals, a computer knows what to do to keep the vehicle operating efficiently with many different variables.

Body module

this computer provides memory and other functions for the radio, drivers information center, electronic compass, trip computer, navigation, exterior and interior lights, etc..

Engine control module

this computer used sensor inputs to control engine idle speed, fuel injection, ignition timing, emissions control devices and other operating parameters.

HV power control module

this module consists of a set of electrical and electronic circuits that alter current and route it between the battery pack and motor generator in a hybrid vehicle.

hybrid control module

this module control the power control module and motor generator to keep the battery pack operating at the optimum temperature and state of charge.

Power train control module

this module is a powerful computer used to monitor and control the engine, transmission and other system.

Transaxle/transmission snsor

this sensor checks transaxle or transmission gear selection oil pressures, parts speeds, loads and other function, a neutral safety switch is a part of a safety circuit to keep the engine from starting when the tranxale/transmission is not in park or neutral.

Solar sensor

this sensor converts sunlight directly into an electrical signal, it is made of a semiconductor material that converts photons (light energy) into direct current.

Air bag module

this small computer controls the vehicle air bag system, this electronic circuit also stores power to deploy the air bags in the event that battery power is severs and lost in a collision.

Ignition module

this small computer used sensor inputs to control ignition timing spark plugs firing or ignition coil pack operation.

Instrumentation module

this small computer used sensor inputs to operate a digital dash display.

Climate control module

this small computer used to control the operation of the heating , ventilation and air conditioning system.

Suspension system module

this small computer used vehicle speed, suspension, and steering sensor inputs to control ride stiffness or shock absorber action.

Antilock brake module

this small computer used wheel speed sensor inputs and other inputs to control antilock brake application.

Brake switch

this type of sensor detect brake pedal application.

Direct sensor

this type of sensor detect the polarity of a moving magnet, this is a variation of a magnetic sensor, unlike a magnetic sensor, it can signal which direction a part is rotating, it can produce signal for north, south, east and west an is used some navigation system.

knock sensor

this type of sensor generates voltage from a physical shock or motion on a crystal, it is sometimes used to listen to a condition, such as engine pinging upon rapid acceleration.

EGR sensor

this type of sensor measure the position of the exhaust gas recirculation valve pintle.

Crankshaft position sensor

this type of sensor measures crankshaft position, rotation, and speed.

optical sensor

this type of sensor used light emitting diodes and photo diodes to produces a digital signal, optical sensors may be used to sense part rotation and speed, these sensors are used in some distributor and as speed sensors mounted outside the speedometer.

DC sine wave

this wave is a curving, fluctuating signals that says at or above zero volts, most magnetic speed sensors produce a low voltage since wave on a test scope.

Erasable programmable read only memory

(EPROM), erasable programmable read only memory can be changed, however, in most cases, the changes can only be made by the manufacturer using special equipment, this type of memory is also responsible for storing semipermannent data, such as odometer or mileage reading for an electronic dash display.

Intake air temperature sensor

(IAT), this sensor measure the temperature of intake air as it enters the intake manifolds, the IAT is also called a manifolds air temperature (mat) or an inlet air temperature sensor.

Analog signal

Gradually changes in strength, ex, sensor internal resistance (and result voltage signal) may smoothly increase or decrease with changes in temperature, pressure or part position, the change in resistance will cause a change in the resulting voltage signal, an analog signal will produce a curve wave or an irregular wave.

The brain (computer processing)

The brain used billions of cells interconnected by linking cells called neurons, each neurons chemically electrically connects tens of thousands of neighboring cells, when the brain ''thinks'' minute electrical impulses travel from neurons to neuron, one simple thought might involve electrical impulses between hundreds of thousands of cells in a specific pattern, this is not unlike the electrical action inside the circuits of a computer.

Nervous system (computer input)

The humans nervous system used chemical electrical signals to control the body, if you touch a sharp needle, nerve cells in your finger ''fire'' and send a signal through a stranded of nerve cells in your hand, up your arm and into your brain, the strand of nerve cells forms a wire that connects your finger and brain. the nerve cells in the tip of your finger are comparable to a sensor or input device in a computer system.

Reflex action (computer output)

The needle prick signal from the nerve endings in your hand activated specific brain cells to fire and produce a chemical/ electrical reaction (pain), a reflex output (voltage) is then produces by your brain (compuyer) ND sent back down the nerves (wires) in your arms, this chemical electrical output signal stimulates the muscles in your arm and hand to pull back, protecting your finger from the sharp project, the reflex action of your muscles is similar to the action of an actuator, or output devices, in a card computer system.