- Contact Us -
Email: Phone: - Links -
Home
310-545-3716
Automotive Electronics Terms/Acronyms
AAR - Auxiliary Air Regulator; a valve which controls idle air and affected by a heater element
AAV - Auxiliary Air Valve; a valve which controls idle air and affected by water temperature,
or a valve which momentarily increases the idle during startup and actuated by vacuum
ABD - Automatic Brake Differential; an electronic control system for traction control which prevents
loss of wheel traction by applying wheel braking to non limited slip differentials
ABS - Anti-Lock Braking; an electronic control system which prevents wheel lockup, reducing the
loss of wheel traction and thus enhancing skid avoidance
ADC - Analog to Digital Converter; a semiconductor device which samples an analog signal and
converts it to a binary number that represents the analog value, i.e. all engine parameters
(e.g. temperature) are analog values which must be converted for processing by the MCU
AFI - Adaptive Fuel Injection; a fuel injection system which can adapt to engine changes over
time and control emissions, e.g. intake air leaks, fuel pressure changes & engine wear
AFM - Air Flow Meter; a device used to sense intake air volume flow (VAF) for a fuel injection
system, but does not compensate as well for air density as does a AMS/MAFS,
where output = F (density X velocity ^ 2 X area of sensor intake) or,
where V(out) for digital ECM = K X (angular position of flap, 0-110 degrees) or,
where V(out) for analog ECM = K X (sqrt angular position of flap, 0-110 degrees) or,
where V(out) for analog ECM = K X V (air volume - cubic meters/sec) = VAF or,
where MAF = density X VAF
AFR - Air Fuel Ratio; the ratio of intake air to intake fuel, ideally 14.7 for emissions control
and 12.6 for maximum torque, AFR = 14.7 X (CO2 - CO) / (CO2 - O2 / 2)
AGS - Automatic Transmission Controller; an ECU which controls the transmission
AMS - Air Mass Sensor; a device used to sense the quantity of the intake air mass for a fuel
injection system, which results in a more precise fuel injection control than an AFM,
where output = density X velocity X area of sensor intake, e.g. MAFS
ASR - Acceleration Slip Reduction; an electronic control system usually integrated in the ABS
system which reduces wheel slip, e.g. snow, ice, & mud, during acceleration by applying
wheel braking to the slipping wheel
BAS - Brake Assist System; an electronic control system which prevents wheel lockup, reducing the
loss of wheel traction and thus enhancing skid avoidance, e.g. ABS
BFI - Bank Fuel Injection; a fuel injection system where all cylinder injectors operate at once
BTDC - Before Top Dead Center; a timing position before the upper most piston position
on the crank cycle
CAFE - Corporate Average Fuel Economy; a U.S. federal regulation which defines the required
average fuel economy of an automobile manufacturer
CAN - Controller Area Network; a serial data network used to transfer control data between
various ECUs of an automotive system & defined by SAE J2284 & ISO 11898,
also referred to as VDB, similar electrically (physical layer) to RS-485
CARB - California Air Resources Board; an agency which sets air quality standards & provides
guidelines to be defined by the SAE for automotive emissions controls compliance
CAT - Catalytic Converter; a device used to reduce emissions with Lambda controlled to 1.0
CCU - Climate Control Unit; the main element of a climate control system which controls all
other elements, e.g. valves, mixing flaps & solenoids
CDI - Capacitive Discharge Ignition; an ignition system where energy is stored in capacitor
and transferred to an ignition coil to develop an ignition spark
CEL - Check Engine Light; an instrument panel light used to indicate an engine fault which
can be read by a diagnostic tester, also called a MIL
CHT - Cylinder Head Temperature; a NTC sensor which is used to determine the
cylinder head temperature, e.g. TS, ECT
CIS - Continuous Injection System; a fuel injection system where fuel is provided to each
independent cylinder continuously at a varying pressure based on intake air flow and
engine load, either electrically or electronically controlled for performance
CKP - Crankshaft Position and Speed Sensor(s); a sensor or sensors which is (are) used to
provide a crankshaft position reference and a speed signal(s)
CMP - Cam Position Sensor; a sensor used to determine TDC for SFI and/or DIS systems
CO - Carbon Monoxide; a toxic gas which results from an incomplete combustion process,
the lack of adequate oxygen, i.e. a low AFR
COP - Coil-On-Plug; an ignition system where each cylinder has a unique ignition coil,
also referred to as Direct Ignition System (DIS)
CO2 - Carbon Dioxide; a non-toxic gas which results from a complete combustion process
CSV - Cold Start Valve; a valve used on early fuel injection systems to provide fuel enrichment
for cold starts, i.e. controlled by the starter solenoid (+) and the thermal time switch (-)
Cycle - OBDII Self Test; a test of the basic functioning of the emissions control system which
includes; TWC efficiency, O2 sensor aging, SAI diagnosis, fuel tank venting, and
TRA & FRA range diagnosis
D-Bus - Diagnostics Bus; a bidirectional bus used to access DTCs, pin 7 of OBDII connector
DI - Direct Injection; a fuel injection system where fuel is injected directly into the cylinder
versus into the intake manifold
DIS - Direct Ignition System; an ignition system where each cylinder has a unique ignition coil,
also referred to as Coil-On-Plug (COP)
DLC - Diagnostic Link Connector; a standardized connector defined by OBDII (J1962) for
DTC access; pin 4 - chassis grd, pin 5 - signal grd, pin 7 - K Line (ISO 9141), ,
pin 16 - +12V, pin 6 - CAN high, pin 14 - CAN low, pin 15 - L line (ISO 9141),
pins 2 & 10 (J1850), pins 1, 3, 8, 9, 11, 12, 13 vehicle specific
DM - Diagnostic Module; an ECU which provides engine monitoring & diagnostics for the
distributed engine management system (multiple ECUs for fuel, ignition, & throttle)
used by Mercedes Benz vehicles prior to that functionality being integrated into a single
ECM. OBDI necessitated this ECU (N59) for 1992 vehicles. On ODBII vehicles,
the DM (N59/1) communicates with other ECUs resulting in additional ECU access
via the DLC. Later vehicles utilized the OBDII CAN pins 6/14 for direct ECU access
DME - Digital Motor Electronics; an ECM which integrates both a fuel injection system and
a ignition system and named by Bosch/Porsche/BMW, e.g. Porsche DME,
BMW DME, also called Motronic
DSC - Dynamic Stability Control; an electronic control system which reduces lateral acceleration
which may result in a loss of wheel traction causing the vehicle to spin by reducing engine
torque and thru controlled wheel braking
DSP - Digital Signal Processing; a method of analyzing an analog signal by converting it into
a digital form and then further converting it from the time domain to the frequency domain
DTC - Diagnostic Trouble Code; a fault code provided by the diagnostic section of an ECU,
may include a description of the fault in addition to a numeric code
ECM - Engine Control Module; the main element of any automotive engine management system,
e.g. fuel injection/ignition control unit, Motronic unit, or DME unit
ECT - Engine Coolant Temperature Sensor; a NTC sensor which is used to determine the
cylinder head temperature, e.g. CHT, TS
ECU - Electronic Control Unit; a functional element of an automotive electronic system,
e.g. ECM, fuel injection unit, transmission control unit, CCU or cruise control unit
EEPROM - Electrically Erasable & Programmable Read Only Memory; a semiconductor
memory device which can be electrically programmed and erased externally,
also referred to as flash memory or flash EPROM
EFI - Electronic Fuel Injection; a fuel injection system where fuel is injected at a constant
pressure but with varying injector opening times based on numerous variables,
e.g. engine temperature, RPMs & load
EGR - Exhaust Gas Recirculation; the feedback of the exhaust gas to the intake to reduce NOx,
whereby the combustion chamber temperatures are reduces. The conditions for a typical
EGR system to operate are; a light engine load, an intermediate engine RPM, and an
engine at normal operating temperature
EGS - Electronic Getriebe System; an ECU which controls the transmission
Egas - Electronic Throttle Actuation; a Porsche ECM with an electronically controlled throttle body
EHA - Electric Hydraulic Actuator; a device to control the fuel pressure on a electronic CIS
fuel injection system for cold running & emissions
EML - Electronic Motorized Luft; electronic actuated throttle control system, e.g. drive-by-wire
EPA - Environmental Protection Agency; a U.S. Government agency which sets environmental
standards
EPROM - Erasable Programmable Read Only Memory; a semiconductor memory device
which can be electrically programmed externally and erased using a UV light
EVAP - Evaporative Emission System; an emission system which controls fuel evaporations into
the air
EWS - Electronic Immobilization System; an anti-theft system that has an electronic ignition key
coded to the vehicle, which inhibits the ECM from functioning
EZK - Electronic Ignition with Knock Control; an ignition system which utilizes knock sensors
to prevent engine knock the result of fuel grades, engine temperatures, & engine loads
FFT - Fast Fourier Transform; a digital signal processing algorithm which can be used in
an automotive knock control system whereby an actual analog time domain knock signal
is converted into frequency domain signals to be compared to a characteristic frequency
domain composite of the typical knock signal
FRA - Fractional Relative Adaptation; a fuel injection adaptation method used to compensate
for engine/sensor changes under load which affect the AFR, e.g. MAFS output error,
with some ECMs retaining the old FRA values with battery removal & not updating until
closed loop operation returns via the O2 sensors
FV - Frequency Valve; a valve used to vary the CIS control pressure for emissions control
Hall - Hall-Effect Device; a semiconductor device whose conductivity is affected by a magnetic
field, either as a two wire sensor (switch) or as a three wire sensor (powered module)
HC - Hydrocarbons; particulates of unburned fuel, the result of an inadequate AFR
HFM - Hot-Film Mass Air Flow Sensor; a mass air flow sensor whose output voltage is based
on a temperature differential across a heated resistive film network, a type of AMS
IAC - Idle Air Control; an air valve controlled electronically used to maintain a constant engine
idle, e.g. ISV
IAT - Intake Air Temperature; a NTC sensor which is used to determine intake air temperature
for the AFM or AMS
IDI - Inductive Discharge Ignition; an ignition system where the spark energy is stored in the
ignition coil
IKE - Integrated Cluster Electronics; an instrument cluster which contains vehicle info, e.g. VIN
ISO - International Standards Organization; an organization which defines product specifications
to maintain a universal standard, e.g. ISO 9141 which defines an ECM interface protocol
K Line - Data Port; a bidirectional serial communications port used to access ECU data
as defined by ISO 9141 using RS-232 interface protocol with level conversion,
0/+12 volts to +/-12 volts for RS-232
KCS - Knock Control System; an adaptive feedback ignition system used to prevent detonation
while optimizing the ignition advance to achieve maximum torque. One approach uses
digital signal processing (DSP) where an analog knock signal in the time domain is
converted into a digital form and analyzed, using one of the Fourier Transforms (FT),
in the frequency domain.
KS - Knock Sensor; a sensor which provides an indication of a too advanced ignition timing
L Line - Command Port; a unidirectional serial communications port used to access ECU data
as defined by ISO 9141 using RS-232 interface protocol with level conversion,
0/+12 volts to +/-12 volts for RS-232
Lambda - the ratio of the actual AFR to the ideal AFR of 14.7 & derived from an O2 sensor
LH - Hot-Wire Mass Air Flow Sensor; a mass air flow sensor whose output voltage is based on
a temperature differential across a heated wire in a resistive bridge network, a type of AMS
MAFS - Mass Air Flow Sensor; a sensor used to measure the quantity of intake air mass
either by hot wire or hot film technology, e.g. AMS
MAP - Manifold Absolute Pressure; intake manifold pressure used to determine engine load
MCU - Microprocessor Control Unit; the main section of an ECM which contains the digital
processing elements, i.e. the microprocessor, the ADCs, and the memory devices
MFI - Mechanical Fuel Injection; a fuel system where a mechanically controlled fuel distributor
injects fuel into each independent cylinder based on engine RPMs and throttle position
MIL - Malfunction Indicator Light; an instrument panel light used to indicate an engine fault
which can be read by a diagnostic tester, also called a CEL
Motronic - Bosch ECM; an ECM which integrates the ignition and fuel injection functions,
e.g. BMW Motronic, Porsche Motronic, also called DME
MPFI - Multi-Point Fuel Injection; a fuel injection system which injects fuel to each independent
cylinder, e.g. BFI or SFI
NOx - Oxides of Nitrogen; particulates of nitrogen which result from excess combustion heat
(T > 2300 degrees F) & oxygen, e.g. excessive AFR, or a too advanced ignition timing,
Air = N2 (78%) + O2 (21%), N2 + O2 > NOx
NTC - Negative Temperature Coefficient; the typical characteristic used for temperature sensors,
sensor resistance decreases with increasing temperatures, e.g. engine head/CCU sensors
O2 Sensor - Oxygen Sensor; a sensor which provides an output used to determine Lambda,
more appropriately called a Lambda sensor, either narrow band (voltage range
of ~ .20 -.80 volts), or wideband (current range of ~ +/- 3-5 ma)
OBDI - On-Board Diagnostics I; a 1988 regulation requiring a MIL, engine diagnostics,
non-standard diagnostic codes, non-standard diagnostic connector & electrical interface,
and volatile fault memory
OBDII - On-Board Diagnostics II; a 1996 regulation requiring standardized diagnostic codes per
SAE J2012 and a standardized connector per SAE J1962, a non-volatile fault memory,
and a MIL, with emphasis on emissions & system failures complying with J1850 or
ISO 9141-2 protocol
OEM - Original Equipment Manufacturer; a producer which manufactures the initial product
P-Code - Trouble Code; a numeric fault code provided by the diagnostic section of an ECU,
generally related to the engine ECM, e.g. DTC
PCM - Power Control Module; the main element of any automotive engine management system,
also commonly called ECM
PROM - Programmable Read Only Memory; a semiconductor memory device which can be
electrically programmed externally
RS-232 - Serial Send/Receive Protocol; a serial communications protocol used to transmit and
receive data over a two wire connection where each element transmitted is a baud
which consists of a start bit, a stop bit, and typically 8 data bits. Usually a UART
type device is used to control the transmission process.
SAE - Society of Automotive Engineers; an automotive standards setting group
SAI - Secondary Air Injection; an exhaust air injection which is used at initial engine startup
to reduce emissions before the TWC reaches the proper temperature to be effective
SFI - Sequential Fuel Injection; a fuel injection system where each fuel injector provides fuel
at a unique time for each cylinder
SMD - Surface Mount Device; an electronic packaging technology which eliminates component
mounting holes in printer circuit boards and reduces component lead lengths to small tabs
TBI - Throttle Body Injection - a fuel injection system where fuel is injected at one central point
TBS - Throttle Body Switch - a switch mounted on the throttle body to provide idle and WOT
positions, also referred as TVS
TCI - Transistor Controlled Ignition; an ignition system where a semiconductor device is used
as a switch to control the current in an ignition coil, i.e. a type of IDI
TDC - Top Dead Center; the upper most piston position on the crank cycle
TPI - Tuned Port Injection; an early BFI fuel injection system used by GM, later systems were SFI
TPS - Throttle Position Sensor; a device used to determine the position of the throttle butterfly
by providing a variable voltage output as an indication of the angular throttle position, and
can function as a proxy to determine engine load when calculated with the engine RPM
TRA - Time Relative Adaptation; a fuel injection adaptation method used to compensate for engine/
sensor changes at idle, which are short term & small affecting the AFR, e.g. intake air leaks,
and which generally varies equally with +/- values under normal conditions
TRIM - Fuel Injection Adaptation; a function provided by OBDII to correct the fuel injection pulse
width for AFR variations beyond the range of the O2 sensor, e.g. FRA (percent change) -
driving mode (open/closed loop), TRA (millisecond change) - idle mode (closed loop)
TS - Temperature Sensor; a NTC sensor which is used to determine the cylinder head temperature;
CHT, ECT
TVS - Throttle Valve Switch - a switch mounted on the throttle body to provide idle and WOT
positions, also referred as TBS
TWC - Three Way CAT; a catalytic converter which reduces the emissions of CO, HC, & NOx
UART - Universal Asynchronous Receiver Transmitter; a function used for serial communications
between a processor, e.g. a scanner, and an external device, e.g. an automotive ECU via
the K-line, using RS-232 protocol where an element of transmission is a baud
VAF - Volume Air Flow; the quantity of air flow in cubic meters per second measured by an AFM
ValveTronic - Variable Camshaft Timing & Lift; a continuously variable intake & exhaust
camshaft timing system with variable valve lift used by BMW starting in 2001
Vanos - Variable Camshaft Timing; a variable camshaft timing system used by BMW which can
be just variable intake valve timing (starting in 1992) or both intake & exhaust valve timing
and can be continuously variable on later engines, e.g. Mini Cooper S (R56) intake camshaft
VarioCam - Variable Camshaft Timing; a variable intake camshaft timing system used first by
Porsche in its 968 engines and later in its early 996 engines
VarioCamPlus - Variable Camshaft Timing & Lift; a continuously variable intake & exhaust camshaft
timing system with variable valve lift used by Porsche in engines subsequent to VarioCam
VarioRam - Variable Intake System; a Porsche engine intake system used on 1996 and later 993
engines that incorporates a second throttle body to further modify the intake system below the
5200 RPM resonance intake system of the Porsche 964 engine to enhance low end torque
VCA - VarioCam Actuator; a device used to change the camshaft timing to optimize engine torque
VDB - Vehicle Data Buss; a serial data network used to transfer control data between various
ECUs of an automotive system & defined by SAE J2284, also referred to as CAN
VIN - Vehicle Identification Number; a number which is unique to each manufacturer's vehicle
VSS - Vehicle Speed Sensor; a sensor which provides the vehicle speed input to the ECM & IKE
VVT - Variable Valve Timing; variable camshaft timing which may include variable lift
WBO2 - Wide Band Oxygen Sensor; an O2 sensor which provides a linear output current from
a negative .70 ma (rich) to a positive 2.4 ma (lean) with an AFR range from 9 to over 17
WOT - Wide Open Throttle; the maximum open position of a throttle body
WUR - Warm Up Regulator; a device used to control the fuel pressure on a CIS fuel injection
system and affected by engine temperature and a heater element
copyright © 2023 Systems Consulting