Hatch S.N. Computerized engine controls

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622 Appendix B Terms and Acronyms

Honda Term Honda Acronym OBD II Acronym

Constant Vacuum Control valve CVC valve

Crank Angle sensor CA sensor CKP sensor

Electronic Air Control Valve EACV IAC

Engine Control Unit ECU PCM

Exhaust Gas Recirculation EGR EGR

Heated Oxygen Sensor HO

SHO

Idle Mixture Adjuster IMA MC solenoid

Manifold Absolute Pressure sensor MAP sensor MAP sensor

Mass Air Flow sensor MAF sensor MAF sensor

Oxygen Sensor O

Pressure Absolute sensor PA sensor BARO sensor

Programmed Fuel Injection PGM-FI

Sequential Fuel Injection SFI SFI

Temperature Air sensor TA sensor IAT sensor

Temperature Water sensor TW sensor ECT sensor

Throttle Angle Sensor TAS TP sensor or TPS

Figure B–8 Honda terms and acronyms.

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Publisher

Delmar Cengage Learning (formerly Thomson

Learning): http://www.delmar.cengage.com/

General Automotive-Related

Web Addresses

California Air Resources Board:

http://www.arb.ca.gov/homepage.htm

Environmental Protection Agency:

http://www.epa.gov

Fuel Cell Store: http://www.fuelcellstore.com

General Motors’ Mode $06 data:

http://service.gm.com/gmspo/mode6/index.html

How Stuff Works: http://www.howstuffworks.com

Scan Tools and Lab Scopes

AES Wave: http://www.aeswave.com

Fluke Corporation: http://www.fluke.com

Snap-on Tools: http://www.snapon.com

PC-Based Scan Tools and Lab Scopes

AutoEnginuity: http://www.autoenginuity.com

Automotive Test Solutions:

http://www.automotivetestsolutions.com

AutoTap: http://www.autotap.com

EASE Diagnostics: http://www.OBD2.com

Professional Organizations

Automotive Service Excellence (ASE):

http://www.ase.com

Identifix: http://www.identifix.com

International Automotive Technicians’ Network:

http://www.iatn.net

National Automotive Technicians Education

Foundation (NATEF): http://www.natef.org

North American Council of Automotive Teachers

(NACAT): http://www.nacat.com

Society of Automotive Engineers:

http://www.sae.org/servlets/index

Training

ATech: http://www.atechtraining.com

Lincoln College of Technology, Denver, Colorado

(formerly Denver Automotive & Diesel College):

http://www.lincolnedu.com/campus/denver-co

Lincoln Educational Services:

http://www.lincolnedu.com

Appendix C

Automotive-Related Web Addresses

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625

A4LD transmission (automatic four-speed

light-duty)—An overdrive transmission fea-

turing a PCM-controlled torque converter

clutch for rear-wheel-drive vehicles.

AC—A parts manufacturing and distribution divi-

sion of General Motors.

Accumulator—A reservoir located between the

evaporator (under-dash unit) and the com-

pressor of an air-conditioning system. It al-

lows refrigerant and any remaining liquid to

separate. Also used to describe a component

in any hydraulic circuit (such as an automatic

transmission) that moderates the application

of some clutch or band.

Active command—A command sent to a PCM

or other control module that commands or

instructs the module to energize and de-

energize an actuator or other output circuit.

Active Fuel Management (AFM)—A variable dis-

placement system in which the PCM disables

cylinders to improve fuel economy when en-

gine load is light. The selected cylinders are

disabled by turning off the fuel injector and

spark and then disabling the ability of the

valves to open through a specially designed

lifter, thus reducing pumping losses by allow-

ing the cylinder to act as an air spring.

Active voltage—A voltage that is actively pulled

either high or low by a computer circuit.

Actuator—Any mechanism, such as a solenoid,

relay, or motor, that when activated causes a

change in the performance of a given system

or circuit.

Adaptive cruise control—A cruise control sys-

tem that can reduce engine torque and even

apply the brakes lightly to maintain a preset

gap to a vehicle ahead.

Adaptive memory—The ability of an engine

control computer to assess the success of

its actuator and sensor signals and modify its

internal calculations to correct them if the de-

sired result is not achieved.

Adaptive strategy—The internal programs by

which the Ford PCM learns from the results

of its monitoring of sensors and activation of

actuators and then modifies its programming

to better achieve driveability, emissions, and

fuel economy objectives.

AdvanceTrac

—A modified antilock brake and

traction control system used by Ford that can

pulse the brakes at any single corner of a ve-

hicle to correct either understeer or oversteer.

The control module can also reduce engine

torque as needed.

Alternate fuel compatibility—The ability of

an engine to run on various fuels. The first

step is the use of methanol- and ethanol-

compatible seals and other parts in the fuel

delivery system. The use of entirely different

fuels, such as natural gas, is predicted to be

the next step toward fuel economy.

Amp or Ampere—A measurement of electrical

current flow within a circuit; equal to 6.25 bil-

lion billion electrons passing a given point in

1 second.

Amperage—Current that is flowing in a circuit.

Glossary

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626 Glossary

Amplitude—The difference between the high

value and the low value in the voltage or cur-

rent waveform of a signal.

Ampule—A strong glass tube that forms the body

of an electrical component such as a vacuum

tube.

Analog—A signal that continuously varies within

a given range and with time taken for the

change to occur.

Anode—A conductor with positive voltage poten-

tial applied.

Arbitration—The process of determining which

node can continue to transmit data on a bus

when two or more nodes begin transmitting

data at the same time.

Armature—A winding of wire designed to create

a strong electromagnetic field when current is

flowing through it.

Asynchronous—Data sent on a data bus in-

termittently and as needed, rather than in a

steady stream.

AXOD (automatic transaxle overdrive)—A

four-speed automatic transmission featur-

ing a PCM-controlled torque converter clutch

used in some front-wheel-drive vehicles.

Background noise—Modern knock sensors are

effective microphones informing the com-

puter of all the engine’s internal sounds,

which the computer then sorts out for fre-

quencies characteristic of knock. By tracking

the increase in background noise with higher

engine speed and load, the computer can

test the effectiveness of the newer type of

knock sensor.

Barometric pressure—The actual ambient pres-

sure of the air at the engine. Because this

pressure varies somewhat with the weather

and altitude, the information is needed to cor-

rectly determine air/fuel mixture.

Baud rate—A variable unit of data transmission

speed (as one bit per second). In a stream of

binary signals, one baud is one bit per second.

Baud refers to the speed at which information

can be sent and received over a data bus.

The limitation comes from the sending and

receiving units, not from the wire itself. Many

modern automotive computers can transmit

and receive at a baud in excess of 10,000. The

term baud is in honor of the Frenchman J. M.

E. Baudot, who is responsible for much of the

early development of unit data transmission.

Belt Alternator Starter (BAS)—A mild hybrid

system on General Motors vehicles that uses

an electric motor/generator (EMG) that oper-

ates as both a 42-V alternator and a 36-V

starter. The EMG is belt-driven by the crank-

shaft and can also belt-drive the crankshaft.

Bidirectional controls—The ability of a scan

tool to send commands to the PCM or other

control module in order to initiate an active

command.

Binary code—This is the form of all the signals

transferred on a data bus. It consists of a se-

ries of on/off signals corresponding to the digits

of the binary numbers, each with a designated

meaning. Binary code transfer is very fast.

Bit—A single piece of information in a binary code

system; somewhat comparable to a single

letter within a word or a single digit within a

number.

Block learn—The adaptive memory systems

used on General Motors cars. As the vehicle

ages and driving conditions change (such as

seasonal weather or altitude), the computer

can make immediate and semi-permanent

changes to the fuel mixture and spark maps

in its keep-alive memory to optimize drive-

ability, emissions, and fuel economy.

Breakout box (BOB)—A diagnostic tool using

special connectors and a terminal box that

enables the technician to check voltages on

all circuits of a harness while the system is in

operation.

Byte—Eight pieces of binary code information

strung together to make a complete unit of in-

formation. Certain newer onboard computers

recognize either 16 or 32 bits of information

as representing a byte (known as 16-bit or

32-bit computers).

C3I—A name used by General Motors to describe

its three-coil ignition system with a module in-

stead of a distributor.

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CALPAK—A removable part of the PCM that

plugs in like the PROM and is primarily re-

sponsible for storing information regarding

fuel injection calibration. Used on the GM

2.0-L engine.

Capacitor—An electric storage device used in

most pressure sensors by Ford EEC IV sys-

tems. The unit’s capacitance is transformed

into a frequency signal internally and sent to

the PCM.

Carbon dioxide (CO

)—A molecule that contains

one carbon atom and two oxygen atoms.

A nontoxic emission produced by proper

combustion taking place in the engine with

enough oxygen present. CO

levels are an

indication of combustion efficiency, with high

levels desired.

Carbon monoxide (CO)—An oxygen-starved

molecule that contains one carbon atom

and one oxygen atom. A toxic emission pro-

duced by combustion taking place in the

engine with a shortage of oxygen present.

A CO molecule will eventually seek out an

oxygen atom and transform itself to CO

In the interim, exposure to CO can cause

headaches, dizziness, nausea, and death.

CO has no taste, odor, or color and cannot

be detected by human senses.

Catalyst—An agent that causes a chemical re-

action between other agents without being

changed itself.

Cathode—A conductor with negative voltage po-

tential applied.

Central Multiport Fuel Injection (CMFI)—A fuel

injection system used by General Motors

on Vortec engines that delivers fuel from a

single, centrally located fuel injector through

nylon tubes and spring-loaded poppet valves

to spray fuel on the back side of each cyl-

inder’s intake valve. As a result, only air is

moving through the intake manifold, similar to

most port-injected engines.

Central Sequential Fuel Injection (CSFI)—A

fuel injection system used by General Motors

on Vortec engines that is similar to the CMFI

system except that multiple injectors are

used to deliver fuel to each cylinder by way of

nylon tubes and poppet valves. The injector

solenoids are centrally located between the

upper and lower halves of the intake mani-

fold.

Clamping diode—A diode placed across a coil or

winding to trap the voltage spikes produced

when the device is turned off.

Clock oscillator—The electronic device within

every computer that produces a continuous

stream of voltage pulses. The frequency of

these pulses establishes the computer’s

clock speed.

Close-coupled catalytic converter—Catalytic

converters that are mounted directly adjacent

to the exhaust manifolds, thereby allowing

them to reach operating temperature more

quickly following a cold start.

Closed loop—The triangular relationship between

a computer, an actuator, and a sensor that

allows the computer to monitor the results

of its own actuator control through a feed-

back signal from the sensor (or circuit). This

concept may be used with certain computer-

controlled actuators or systems such as air/

fuel ratio control, EGR control, fuel pump

and ignition system monitoring, Electronic

Automatic Temperature Control (EATC) sys-

tems, antilock brake systems, and speed

control systems.

Closed loop/open loop—Closed loop is the

mode in which the computer adjusts the air/

fuel mixture in response to signals from the

oxygen sensor, which in turn respond to the

changed mixture ratio. Open loop refers to

control of the mixture based on other informa-

tion inputs, but not the oxygen sensor signal.

Component ID (CID)—An identification code,

usually a hexadecimal value, that identifies a

component in a computerized engine control

system. CIDs and their related information

can be displayed using a scan tool. The re-

lated specifications often may be looked up

at a manufacturer’s Web site.

Compound—A molecule that contains atoms of

two or more elements.

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Computer Controlled Coil Ignition (C3I)—A

waste spark ignition system using Hall effect

CKP and CMP sensors. Introduced by Gen-

eral Motors in 1984.

Concentration sampling—A method of gas

analysis used today by most gas analyzers

in automotive shops. It has a probe that is

inserted into the exhaust pipe. The probe

allows the analyzer to sample only a small

percentage of the total exhaust gas vol-

ume. Each of the gasses is measured as

a percentage, or concentration, of the total

sample. The resulting measurements are

expressed as either percent or parts per mil-

lion (ppm), with ppm simply being a smaller

proportion.

Constant volume sampling (CVS)—A method

of gas analysis that requires that all of the

exhaust be captured and measured along

with enough ambient air to create a known

volume of gasses. Then the density of this

known volume is calculated. Finally, the con-

centration (percentage) of each gas is calcu-

lated to determine how many grams of each

gas is being expelled from the exhaust sys-

tem. The analytical computer is also able to

use dynamometer readings to determine the

distance that the vehicle has traveled in any

instant in time or over a longer time period.

At this point each gas is calculated as grams

per mile (GPM).

Continuous injection—One of the two kinds of

fuel injector fuel-spray techniques, the other

being pulsed injection. A continuous injector

(basically limited to the Bosch K-Jetronics

systems) sprays fuel whenever the engine is

running. The quantity of fuel injected is de-

termined not by the injectors but by the fuel

distributor, a separate component.

Continuously variable transmission (CVT)—A

transmission that transfers optimum torque

from either a gasoline engine or an electric

motor (or from both) to the drive wheels re-

gardless of vehicle speed or load. The driver

never has to “shift gears” as with normal mul-

tispeed transmissions.

Continuous monitor—A monitor that is moni-

tored continuously by the PCM.

Conversational Speech Interface Tech-

nology—A voice recognition technology

used by Ford that allows the driver and/or

pas senger to carry on a normal dialogue

with the vehicle. The resulting dialogue on

the part of the vehicle sounds more like a

real person than a robot. Equipped with a

50,000-word vocabulary, the driver/ passenger

does not have to memorize specific voice

commands, as do some voice recognition

systems.

Current ramping—The use of a lab scope (digi-

tal storage oscilloscope, or DSO) to look at

current waveforms of load components or ac-

tuators, using a low-current probe to capture

the waveform. The name comes from the fact

that current builds slowly when turned on,

causing an upslope, or upward ramp, to ap-

pear on the waveform.

Data bus network—The data bus network is

the information transfer harness between

the elements on a multiplexing system. In

some vehicles, this consists of a special pair

of twisted wires going to each element. The

wires are twisted to prevent introduction of

spurious signals from electrical fields gener-

ated by speed sensors, horn and headlight

circuits, radios (particularly high-power or

CB), and spark plug cables. Many newer sys-

tems use a single-wire data bus design. The

serial data on a single-wire bus has a wave-

form that is trapezoidal in shape. This allows

the nodes that are communicating on the bus

to distinguish between the sharp change of

an induced voltage spike and a binary bit of

information.

Data link connector (DLC)—The 16-terminal

connector on an OBD II vehicle that allows

a scan tool to be connected to communicate

with the onboard computers. When con-

nected to the DLC, the scan tool becomes a

node on the data busses that connect to the

DLC. Sometimes also called a “diagnostic

link connector.”

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Data stream—The communication between a

scan tool and an onboard computer when the

scan tool is connected to the data link con-

nector (DLC) and the ignition switch is turned

on. The communication is in the form of bi-

nary code (serial data); it allows either one-

way or two-way communication between the

scan tool and the onboard computers.

Demultiplexor—An electronic chip that, when

built into a node, gives it the ability to receive

and decipher messages on a data bus.

Diagnostic routines—A section in the service

manual that lists possible causes of a drive-

ability complaint. It is the beginning point of

the diagnostic procedure once the complaint

has been verified.

Diagnostic trouble code (DTC)—A set of alpha-

numeric sequences the computer stores in

its memory when it senses failures in certain

sensor or actuator circuits. DTC is the term

used in OBD II literature; trouble codes

or fault codes were the terms used before

OBD II.

Digital—A voltage signal that is either of two volt-

age values but does not vary in a continuous

fashion between them. Typically these sig-

nals will be a voltage that is turned either on

or off but may also vary between two voltage

values that are both above ground. On a lab

scope, the change of voltage (either high or

low) shows a sharp, vertical edge.

Digital storage oscilloscope (DSO)—A lab

scope that displays a computer-generated

waveform that may be frozen, measured,

stored, downloaded to a PC, and printed

out. The on-screen adjustments include cou-

pling, ground level, volts per division, time

per division, and trigger characteristics; they

are similar to an analog lab scope. A DSO

is most often used to capture voltage wave-

forms over the time shown on the screen but

may also be configured with a low-current

probe to capture current waveforms (known

as current ramping ). A DSO is designed to

perform pinpoint tests of a circuit or compo-

nent.

Digital volt ohmmeter (DVOM)—A diagnostic

tool that allows the technician to view nu-

merical readings relating to voltage, amper-

age, and resistance measurements. Many

DVOMs can also be used to measure fre-

quency, duty cycle, pulse width, RPM, and

temperature. High-end units also may include

a bar graph to improve update resolution.

Auto-scaling DVOMs are designed to rescale

automatically according to the values being

measured. A DVOM is designed to perform

pinpoint tests of a circuit or component.

Diode—The simplest semiconductor, consisting

of only two semiconductor elements placed

back-to-back. A diode operates as an elec-

trical one-way check valve with no moving

parts.

Direct ignition/waste spark ignition—A direct

ignition system eliminates the ignition dis-

tributor and fires spark plugs directly from the

coil. If the direct ignition system is of the waste

spark type, each coil fires two spark plugs si-

multaneously. One spark occurs at the end of

its cylinder’s compression stroke, just before

the power stroke; the other spark occurs at

the cylinder 360 degrees apart in firing order

from the first, during the end of that cylinder’s

exhaust stroke. The two sparks are of oppo-

site polarity. Non–waste spark direct ignition

systems use one coil per spark plug.

Displacement on Demand (DOD)—General

Motors’ original name for their Active Fuel

Management (AFM) system, which is a vari-

able displacement system in which the PCM

disables cylinders to improve fuel economy

when engine load is light. The selected cyl-

inders are disabled by turning off the fuel

injector and spark and then disabling the

ability of the valves to open by use of a spe-

cially designed lifter, thus reducing pumping

losses by allowing the cylinder to act as an

air spring.

Driveability—Those factors, including ease of

starting, idle quality, and acceleration without

hesitation, that affect the ease of driving and

reliability.

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630 Glossary

Drive cycle—A series of operating conditions

that allows the PCM to complete all of the

OBD II emissions-related monitors.

Dual in-line package (DIP)—Refers to an inte-

grated circuit chip with two rows of legs (ter-

minals).

Duty cycle—The portion of time during each

cycle when an electrical device is turned on,

when the device is cycled at a fixed number

of cycles per unit of time.

E-cell—A module containing a cathode and an

anode, each of which is gradually sacrificed

as current passes through it, eventually caus-

ing the circuit to open.

EEPROM—Electronically erasable programma-

ble read-only memory, an improved and up-

dated type of PROM. Like the PROM, it can

retain tabular information for the PCM even if

power is withdrawn from the computer. Unlike

the PROM, the information in this memory

can be changed by the computer. Also unlike

the PROM, the EEPROM is a nonreplace-

able part of the computer.

Efficiency monitoring—The diagnostic testing

performed by a computer, specifically in its

ability to compare input values to each other,

or to operate an actuator while watching the

change in a related input circuit. Also known

as rationality testing.

EGR temperature sensor—On late-model cars,

particularly those that are OBD II–compliant,

the EGR temperature sensor serves to signal

the computer that recirculated exhaust gas

flows when it sends the command for it to do

so. This sensor makes use of the fact that the

exhaust gas is very hot, so the temperature

of the passage provides a reliable indicator of

exhaust flow.

Electrical—Refers to a circuit that performs

physical work in the creation of heat, light, or

magnetism. An electrical circuit operates at

relatively high amperage. An electrical circuit

may or may not be controlled electronically.

Electrical schematic—A map of an electrical

system’s circuitry that can be used by the

technician as a diagnostic aid. It is most often

used to increase the level of understanding of

an unfamiliar system.

Electromotive force—Refers to the electrical

pressure that pushes current flow. It is com-

monly called voltage and is measured in

volts.

Electronic—Refers to solid-state control circuits

that are placed in control of electrical circuits.

Electronic circuits operate at relatively low

amperage and consist of solid-state elec-

tronic parts such as diodes and transistors.

Electronic Throttle Control (ETC)—A system,

sometimes referred to as “drive-by-wire,”

that physically decouples the throttle pedal

from the throttle plate(s), thus eliminating the

traditional throttle cable. An accelerator pedal

position (APP) sensor provides the driver

demand information to the PCM; the TPS

simply provides a feedback signal. The PCM

then controls the position of the throttle plate(s)

through pulse-width modulated control of a

DC motor. Formerly known by General Motors

as a Throttle Actuator Control (TAC) system,

this system increases the responsiveness of

the engine.

Element—A molecule that has only one type of

atom, as shown in the periodic table, defined

by how many protons, neutrons, and elec-

trons the atom contains.

Enable criteria—The specific operating condi-

tions of the engine and the vehicle that are

required to be present before the PCM will

perform a test such as a drive cycle or a

trip. When the pre-programmed enable cri-

teria have been met, the PCM will perform

a drive cycle to test one or more monitors.

When the PCM needs to verify the presence

or absence of a fault, it will perform a trip with

the enable criteria aimed specifically at the

particular fault.

Engine calibration—Adjustments or settings

that produce desired results, such as spark

timing, air/fuel mixture, and EGR control.

Engine calibration assembly—The portion of a

Ford PCM that contains the necessary pro-

gramming to fine-tune the PCM’s commands

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to the specific needs of a particular vehicle,

similar to a PROM chip on a General Motors

vehicle. On EEC I, EEC II, and EEC III sys-

tems, the calibration assembly is attached

externally to the PCM, is removeable, and

contains an octane adjustment switch. On

EEC IV and EEC V systems, the calibration

assembly is a permanent part of the PCM.

Engine metal overtemp mode—A unique fea-

ture of the Aurora/Northstar engine, whereby

under circumstances of very high engine

temperature (if, for example, the coolant has

leaked out), the computer selectively disables

four of the fuel injectors to prevent a tempera-

ture that would cause permanent mechanical

damage to engine components.

EVAP system pressure sensor—Used on many

OBD II–compliant vehicles to test the fuel

vapor canister system for leaks. On many ve-

hicles, special plumbing allows the MAP sen-

sor to provide this function during the period

between ignition on and engine running.

Exhaust gas analyzer—A diagnostic machine

that samples and displays measurements of

automotive emissions readings, including HC,

CO, CO

, and O

, for diagnostic purposes.

Additionally, some analyzers also measure

and display readings for NO

Fail-Safe Cooling—Ford’s name for the ability

of the PCM to disable fuel injectors to allow

the respective cylinders to simply pump air to

cool the block and cylinder heads.

Feedback—Refers to a signal from a circuit or

sensor that allows a computer to monitor

the results of its own control in a closed-loop

fashion.

Flow bench—A specialty tool, chiefly used at

carmakers’ factories, to properly set feed-

back carburetors to deliver proper air/fuel

mixtures. The settings determined on a flow

bench are normally marked with paint to indi-

cate that they are not to be changed.

Flowcharts—A series of diagnostic charts that

are designed to guide the technician through

the necessary pinpoint tests to identify the

exact cause of a fault.

Flywheel Alternator Starter (FAS)—a mild hybrid

system on General Motors vehicles that uses

an electric motor generator (EMG) operating

as both a 42-V alternator and a 36-V starter.

The EMG is built into a redesigned torque

converter in the area of the transmission’s

bell housing.

Free electrons—Electrons that are loosely held

in an atom’s orbit. These electrons can be

pushed from one atom to another if enough

voltage is applied to overcome their resis-

tance to moving.

Freeze frame data—Whenever an OBD II diag-

nostic trouble code is set, the computer

records the information pertaining to the

sensors, actuators, and operating conditions

that are relevant to the fault. This information

can be pulled from the computer’s memory

with a scan tool and is designed to aid the

technician in diagnosis.

Front and rear oxygen sensors—To ensure that

the engine control system can go into closed

loop quickly, both the front and rear oxygen

sensors include heater circuits to get them to

operating temperature quickly.

Front Electronic Module (FEM)—A Ford con-

trol module that controls the one-touch-down

power window, the horn relay, and the exte-

rior lighting at the front of the vehicle.

Fuel cell vehicle (FCV)—A version of an elec-

tric vehicle that uses hydrogen fuel cells to

provide the electrical power that the motor

(or motor/generator) uses to accelerate the

vehicle’s drive wheels.

Fuel temperature sensor—On some cars, a

sensor mounted in or near the fuel tank to

inform the computer of the fuel temperature.

This information is used to calculate fuel vis-

cosity and susceptibility to vapor lock.

Fuel trim—The ability of the PCM to modify the

base fuel calculation to maintain a stoichio-

metric air/fuel ratio while in closed loop. Fuel

trim is divided into both a short-term fuel trim

(STFT) and a long-term fuel trim (LTFT).

Functional test—A test (that has been pro-

grammed into a computer) designed to aid

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