Impala SS Dictionary
Impala SS Dictionary
A dictionary for Impala SS Afficionados
This page comes at the request of many new members who have troubles with
the abbreviations, part names, etc. that are used in the FAQ, mailing list, and
other locations. In it you will find a hodge-podge of sensor terms, acronyms,
slang, and other stuff that I hope will be useful. If you have a term which you
feel should be included, let me know and
I'll get it in as soon as possible. Thanks.
Entrys for '1'
Special code used on Chevrolet Camaros to indicate that they are equipped
with the racing performance package. This package deletes air conditioning and
several other luxury items and beefs up the suspension. The 1LE intake elbow
is useful for Impala engine modifications
Entrys for '6'
The 6J6 option is two 4" diameter red lights (one left side, one right
side) that face rearward and are mounted inside the car behind the rear seats
and above the rear package shelf (under the rear window). These come on when
you use the brakes or use the turn signals. They are an option on the 9C1. See
Entrys for '9'
Chevrolet order code for the police package option on the Caprice. This is
usually used to refer to parts that only come as part of this package, such as
"9C1 Trunk Mat".
Entrys for 'A'
Acronym for Antilock Braking System. This system prevents the tires from
"locking up" under heavy braking or slick conditions by modulating pressure to
the brakes when sensor determine that the tire is no long rolling. This allow
quicker, straighter stops in most conditions than standard braking.
Abbreviation for the Secondary Air Injection System. This sytem helps
reduce emissions and heats up the catalytic converters more quickly after
startup so exhaust gas conversion can occur sooner. See also: Air Pump.
The enclosure that houses the air filter. Air comes into the "box" from a
small rectangular opening on the front, and is then fed through the air filter
to the top of the box. See also: First
The AIR pump pressurized air from the air cleaner and pumps it back into
the check valves near the exhaust manifolds. This is the key part of the AIR
system. The AIR pump is electric and presents no drag on the engine. See also:
Acronym for assembly line diagnostic link. This is the small black
connector underneath the driver's dash. This connector allows the dealer to
plug in scan tools to test and report the status of the PCM. This is how the
dealer scans for trouble codes. This is also how the PCM can be reprogrammed.
See also: PCM,
Entrys for 'B'
Another name for the resonators that are on used to quiet the Impala's air
intake. See also: Pitchers
Acronym used by owners of black Impalas who feel left out because they
don't have a cool acronym like DCM or DGGM to use. Actually, the official GM
name is Standard Onyx Black, but that isn't used for obvious reasons. Usually
taken to mean Bad to the Bone Black. See also: DCM, DGGM.
Acronym for Blue Bow Tie. This is a part from the 97 Cavalier that will
drop into the same place the silver bow tie on the front of the Impala grill
is from the factory. It seems to look better on the DGGM Impalas than the red
bow tie. See also: RBT, CRBT, DGGM.
Acronym for Brake Transmission Shift Interlock. This is a solenoid that
prevents you from shifting out of park unless your foot is pressing on the
brake pedal. This is touted as a safety feature, but is commonly thought to be
a direct result of the lawsuits filed by some Audi owners claiming "unintended
acceleration" of their cars when they were started.
Entrys for 'C'
Module attached to the exhaust manifold that, when heated, can convert the
harmful emissions of the engine to relatively harmless gasses. It contains
very rare and expensive metals for this process. See also: Export
Acronym for Center High Mounted Stop Lamp, which is the third brake light
located at the bottom of the rear window.
Clear Flood Mode
A special starting mode that allows for clearing of excess fuel in the
engine. It is made to emulate the method for clearing floods in carburated
cars. The throttle must be depressed to 80% or more. The PCM will then lean
the air/fuel mixture out to 20:1 to clear the flood. Clear flood mode is
automatically shut off when engine RPM is greater than 300 RPM.
Closed Loop Mode
A run mode of the engine when it has warmed up and is using mainly the
oxygen sensor for very accurate monitoring and control of the air fuel ratio.
In this mode, the engine is running very close to stoichometric (14.7:1). See
Cold Air Induction
A general classification of mechanisms designed to get cooler air from
outside the engine compartment into the engine intake tract. This is usually
accomplished by some sort of scoop or ducting to the outside.
Acronym for Cavalier Red Bow Tie. This bow-tie is a drop-in replacement
for the bow-tie on the grill of the stock Impala. See also: BBT, RBT.
Entrys for 'D'
Data Link Connector
A 16 pin connector located underneath the instrument panel on the drivers
side. This connector is used to verify correct engine operation before the
engine leaves the assembly plant and also by technicians to retrieve DTC's
stored inside the PCM. This connector can also be used to flash the PCM with a
new program. See also: Flash, DTC, PCM.
Acronym for Dark Cherry Metallic, one of the available colors for the
Impala in 1995 and 1996. See also: GGM.
Acronym for Dark Green Grey Metallic, one of the available colors for the
Impala in 1995 and 1996. See also: BBB, GGM, DCM.
Diagnostic Trouble Code
A special code stored inside the PCM when a malfunction is indicated.
These codes may be retrieved and examined using some type of scan tool
connected to the DLC. To clear touble codes, the battery must be disconnected
from the PCM. A DTC does not mean that the engine should be stopped
immediately, but that the cause of the DTC should be checked as soon as
possible. See also: Scan Tool,
Acronym for Data Link Connector. See also: Data
Acronym for Daytime Running Lights. This GM option turns the headlights on
at a reduced voltage during all operating conditions. During nighttime
operation, the headlights are brightened and the rest of the running lights
and the tail lights are also turned on. This option is required in Canada, but
can be fitted to US models. This option is technically not compatible with the
Twilight Sentinel, but you do get the basic twilight sentinal functionality.
The front lamps just don't go off during daylight hours. On pre-1996 cars, the
light sensor was not included with the package, so the tail lights had to be
turned on manually at dusk. See also: Twilight
Acronym for Diagnostic Trouble Code. See also: Diagnostic
Entrys for 'E'
Acronym for Engine Coolant Temperature. This sensor is mounted in the
coolant pump and sends engine temperature information to the PCM. The sensor
is a thermistor that changes internal resistance as the temperature changes.
When the resistance is high, the PCM interprets that the engine is cold. When
resistance is low, the voltage through the wire will decrease and the PCM will
interpret it as a warm engine. The ECT is located on the front of the engine,
just below the water pump. See also: PCM.
Acronym for Electronically Erasable Programmable Read Only Memory. This is
more commonly referred to as flash memory. This type of memory is to store the
engine control parameters in the PCM. The EEPROM in the PCM can be
reprogrammed using the Tech-1 scan tool. See also: Scan Tool,
Tech 1, flash, PCM.
Acronym for Exhaust Gas Recirculation. This sytem reduces emissions,
specifically Nitrogen Oxides caused by high combustion temperatures and
excessive oxygen. It does this by decreasing combusion temperatures and
displacing oxygen with spent exhaust gases. The main element is the EGR valve
mounted on the intake manifold and operated by vacuum.
Abbreviation for the Evaporative Emmisions Control System. This system
utilized a charcoal canister to hold vapors from the fuel tank while the
vehicle is not operating. When the engine is running, the vapor is purged from
the canister into the normal intake path and consumed in the normal combustion
Pipes that can be used in place of the catalytic converters for export use
or off-road use only. These are used where there is no unleaded fuel
available, since leaded fuel would ruin the catalytic converters See also: Catalytic
Entrys for 'F'
First base is a common slang term for the rectangular, black resonator
that is placed between the MAF and the intake elbow. This resonator rests on
top of the radiator. It is called first base because of its close relationship
to the Home Plate resonator on top of the engine. See also: Home
Flash memory is a non-volatile form of read-only memory that is used in
the Impala to store the computer program that controls the engine. It is
located in the PCM. On earlier cars, this is known as "the chip" and is
commonly replaced with a higher performance program stored on a different
chip. On LT1 engines, the flash memory is reprogrammed through the DLC, which
is often referred to as "flashing" the PCM. See also: DLC, PCM.
This is often the part of the PCM that is referred to as the "learning"
section. There are two parts of fuel trim: short term and long term. Short
term fuel trim is set using the oxygen sensor inputs to detect a lean or rich
condition. The fuel trim is increase for a lean mixture decreased for a rich
mixture. Over a period of time, if the mixture is continously rich or lean,
this is learned into the long term trim, and the short term is returned closer
to a more ideal position. Short term trim is frozen at the ideal value during
power enrichment to remove the rich condition that results there from long
term memory. See also: Power
Entrys for 'G'
Acronym for Green Grey Metallic, one of the available colors for the
Impala in 1995 and 1996. More commonly referred to as DGGM, for Dark Green
Grey Metallic, but GGM puts it into the TLA (Three Letter Acronym) territory.
See also: BBB,
Entrys for 'H'
Acronym for Heated Oxygen Sensor. The LT1 uses heated oxygen sensors to
determine if the engine is running lean or rich. See also: Oxygen
A slang term invented for the triangular resonator that sits on top of the
engine to reduce the noise level of the intake air path. It is so named for
its resemblance to a common home plate shape in baseball. See also: Pitchers
Acronym for the Hypertech Power Programmer. This device reprograms your
PCM with a custom performance program. You insert it through the ALDL
underneath you dash. It then reads the stock program out, modifies it
according to your parameters, and stores it back. You can reprogram and
deprogram your PCM at will. See also: ALDL, PCM, HPP+, HPPP.
Another name for the Hypertech Power Programmer Plus. See also: HPPP.
Acronym for the Hypertech Power Programmer Plus. This device works much
the same way as the HPP, but allows more parameters to be modified, and will
eventually allow custom cartridges to be inserted to function as scan tools
and other functions. This is the second generation of the HPP. See also: ALDL, PCM, HPP+, HPP.
Acronym for the Heating, Ventilation, and Air Conditioning system
Entrys for 'I'
Acronym for the Idle Air Control valve. See also: Idle Air
Acronym for Incoming Air Temperature. This sensor is mounted in the elbow
that connects to the throttle body and monitored by the PCM. The PCM controls
fuel delivery and spark timing based upon the incoming air density. See also:
Idle Air Control
The purpose of the Idle Air Control valve is to control engine idle speed
to prevent stalls based upon changes in engine load. The IAC control is
mounted in the throttle body and can bypass air around it based upon PCM
Acronym for In My Humble Opinion. Used in internet e-mail correspondence
to distinguish fact from opinion.
Entrys for 'J'
Acronym for Jet Assisted Take Off. The military uses JATO rockets to
assist in getting heavy planes off of the ground. There is an urban legend
about someone who strapped one to their Impala out in the desert and then
crashed into a cliff doing around 300MPH. The story is a complete fabrication,
and ends up being posted to the Impala mailing list about once a month.
Entrys for 'K'
Two sensors are mounted in the block to detect knock or detonation in the
engine. If it is detected, the PCM retards the spark to prevent damage to the
engine. This allows for variations in octane levels without damaging the
engine. Often referred to by the acronym KS. There is also a module inside the
PCM that is used to monitor for knock from the sensors. See also: KS.
Acronym for the Knock Sensor. See also: Knock
Entrys for 'M'
Acronym for the Mass Airflow Sensor. The MAF sensor used on the Impala is
the hot-wire type. The output frequency from the MAF is a function of the
power required to keep the air flow sensing elements (hot wire) at a fixed
temperature above ambient. As air flow increases, a greater amount of current
is required to keep the wires at a constant temperature due to the cooling
affect of the increased quantities of air. The MAF is directional and must be
installed in the proper direction.
Malfunction Indicator Lamp
This is the infamous "Service Engine Soon" light. It indicates to the
driver that a problem has occured and that the vehicle should be taken in for
service as soon as possible. The light will go off when the engine is
restarted unless there is a failure in the self-diagnostics of the MIL system.
In any case, a trouble code (DTC) is stored for later retrieval via a scan
tool. A lit MIL does not mean that the engine should be stopped immediately:
rather, the cause of the MIL should should be checked as soon as possible. See
also: SES, DTC, MIL.
Acronym for Manifold Absolute Pressure. This sensor measures the change in
the intake manifold pressure as speed and engine load changes. As the manifold
pressure increases, the air density in the intake manifold also increases.
Acronym for Malfunction Indicator Lamp. See also: Malfunction
Mobil 1 Cap
Special oil filler cap that was supplied on Corvettes equipped with Mobil
1 from the factory. States to use "Mobil 1 Oil Only". Will fit Impalas with
the 'Vette valve covers or stock '94 Impalas. See also: Mobil 1
Mobil 1 Plate
Special notification plate that was supplied on Corvettes equipped with
Mobil 1 from the factory. States to use "Mobil 1 Oil Only". A nice addition
for those Impalas using Mobil 1 oil. See also: Mobil 1
Entrys for 'N'
Acronym for National Association of Impala SS Owners, a nationwide
organization of over 500 Impala SS Owners. Troy Wilrick runs it from Florida, and
there are many regional chapters springing up all over. See my home page for more
Entrys for 'O'
Abbreviation for Heated Oxygen Sensors. See also: Oxygen
Acronym for On-Board Diagnostics II, a system instituted by a Federal
standards committee that forces the engine control system to be able to
monitor for a failure in any sensor in the emmisions control circuitry. This
is only fully implemented on 1996 Impalas. This required PCM changes and an
extra set of oxygen sensors to be fitted to 1996 Impalas.
Open Loop Mode
A run mode of the engine when it is first started. In this mode, the PCM
ignores the oxygen sensors and calculates the air/fuel ratio based upon inputs
from the MAF, ECT, and TP sensors. The system stays in this mode until the O2
sensors have varying values, the coolant temperature has raised to a preset
value, and a preset amount of time has expired. See also: Oxygen
The distributor ignition system on the LT1 engine. This system utilizes an
optical sensor to detect timinng pulses on the crankshaft. The PCM then
receives both a low resolution (4x) and high resolution (360x) signal to
control timing to the injectors.
The LT1 in the Impala engine contains two heated oxygen sensors near the
catalytic converters. These oxygen sensor provide feedback to the PCM that
tells it if the engine is running rich or lean. A voltage of 450mV from the
oxygen sensor indicates that the engine is running perfectly (stoichometric),
which means that all of the air and all of the fuel are being used during the
combustion process. If the value is lower than 450mV, the engine is running
lean, which means that there was too much oxygen in the combustion process. If
it is greater than 450mV, the engine is running rich. The PCM adjusts in both
the short and long term for the effects of the oxygen sensors. The O2 sensors
do not work until they have reached about 600 degress F. Until then, they look
like an open circuit to the engine, and the PCM must "guess" what mixture to
use. Also, the O2 sensors are ignored by the PCM during wide-open throttle
time periods. See also: WOT, PCM.
Entrys for 'P'
Acronym for Personalized Automotive Security System. General Motors
designed anti-theft system. It operates by using a specific resistor in the
ignition key. A signal is sent to the PCM only if the corect resistor is
detected that will enable the starter circuit and the injectors. The car will
not run even if the crank circuit is bypassed (hot-wired). A DTC is stored if
the wrong resistor is sensed by the PCM. See also: DTC, PCM.
Acronym for Powertrain Control Module See also: Powertrain
Acronym for Pressure Control Solenoid. This solenoid allows the PCM to
vary the line pressure to the transmission to make shifts crisper and harder
based upon throttle position, engine RPM, etc. This feature allows for
aftermarket PCM programs to incorporate an electronic "shift kit" without
opening up the transmission.
Acronym for Purple Door Panels. Some Impala door panels come from the
factory with a purple tint to them. They tend to very: some may have a
definite purple color, others may be slightly tinted. We are in the process of
trying to get GM to issue an official TSB on this issue, otherwise, you can
take your chances on getting your local dealer to replace them for you. See
A slang term invented for the rectangular resonator that connects the air
cleaner box to the MAF sensor. Its purpose is to reduce the noise level of the
intake air path. It is so named because of its relationship with Home Plate
and its rectangular shape. See also: Home
A condition entered into by the PCM during wide open throttle (WOT).
During this time, the PCM gives the engine extra fuel for more power. Short
term fuel trim is not used during this mode, nor are the oxygen sensors, since
the mixture is inherently rich. See also: Fuel Trim,
Powertrain Control Module
The heart of the control system on the LT1 engine. It monitors sensors to
retrieve information about engine operation and the various systems that it
controls. It also has the ability to do diagnosis on itself and other parts of
the system, and light the MIL and store a DTC if it senses a problem. See
also: DTC, MIL.
Acronym for Power Steering Pressure switch. When the power steering
pressure is high, the PCM is alerted so that it can raise idle speed to
prevent the engine from stalling under the increased load.
Entrys for 'R'
Acronym for Random Access Memory. This is the PCM's scratch pad. The
processor can read or write from this memory as needed. This memory is
erasable and requires battery power to be retained. If the battery is
disconnected, this memory is lost. The DTC's are stored in RAM. See also: DTC, EEPROM, flash, ROM.
Acronym for Red Bow Tie. The red bow-tie has become the unofficial symbol
of NAISSO. It involves replacing or taping over the OEM chrome bow-tie on the
grill of the Impala. There is a nice unit from the Cavailier that does it
nicely. This is the only part of Jon Moss's concept car that didn't make it
into production. See also: BBT, CRBT.
Acronym for Remote Control Door Lock Receiver, the unit mounted in the
trunk that receives the remote locking keychain signals and sends the signals
to lock or unlock the doors
A baffle meant to reduce noise in an air passageway. There are several
baffles on the Impala. The first is a black rectangular piece after the air
clean but before the MAF. The second is the triangular black plastic piece
that sits on top of the engine. These two resonators serve to reduce air noise
entering the engine. There are also two exhaust resonators just before the
tips at the rear of the car. These serve to reduce exhaust noise. See also: Pitchers
Acronym for Read-Only Memory. There is permanent memory physically
soldered into the boards within the PCM. The ROM contains the overall control
programs. Once the ROM is programmed at the factory, it cannot be changed. It
is non-erasable, and does not require battery power to be retained. See also:
RAM, EEPROM, flash.
Entrys for 'S'
A hand-held electronic tool used to analuze and diagnose control module
systems. It can be used to read DTC's stored in the PCM, monitor sensor data
in real time, or flash the PCM with a new program. The primary tool used GM
technicians is the Tech 1. Other aftermarket tools are also available, such as
JET's Auto X-Ray and the Diacom monitor. These tools are useful for tuning and
for diagnosing faults. See also: Tech 1, PCM, DTC.
Acronym for Service Engine Soon, which is what is commonly displayed on
the Malfunction Indicator Lamp indicator. The lamp is now more properly
referred to as the Malfunction Indicator Lamp, or MIL. See also: Malfunction
Indicator Lamp, MIL.
Slang for the common practice of using PVC tubing from the plumbing
section of your local home goods store to replace the first base resonator.
Two elbows make an almost exact fit between the stock instake elbow and the
air box. See also: First
Acronym for Sequential Multiport Fuel Injection
Slang for the mesh piece of metal inside of the export exhaust pipes. It
resembles a shower drain cover, and is probably in place to quiet the exhaust
as it passes through the straight pipes. Most commonly removed. See also: Export
Acronym for Supplemental Inflatable Restraint, which is the technical term
for GM's version of the air bag.
Acronym for Sewer Pipe Equipped, which refers the the homemade PVC pipe
intakes installed on some cars.
A mode of operation where the engine determines the fuel needs from engine
speed and air density. The air density is computed from the IAT and MAP
sensors. These inputs allow the PCM to compute the amount of fuel it needs to
deliver via the injectors. This method is less accurate than reading the MAF
sensor and is only used if there is a fault in the MAF circuit. On OBD-II
cars, this method is used to check the MAF for errors. This method requires
changes to the PCM to compensate for modifications to the engine. See also: MAF, MAP, IAT.
Super Sport, a moniker commonly given to some of Chevrolets high
performance cars. See also: Z28.
A chemical term used when both elements in a process are completely used
in a reaction. In this case, it refers to the oxygen and the fuel being burnt
in the engine. This air/fuel ratio is usually 14.7:1. See also: Closed
Loop Mode, Oxygen
Acronym for Steering Wheel Controls, which allows you to adjust radio
parameters from buttons placed on the steering wheel.
Entrys for 'T'
The bulbs used in the export headlights that produce a generally brighter
and sharper beam than the standard.
Acronym for Torque Converter Clutch. The torque converter allosw limited
slippage inside of the transmission to allow the engine to spool up into its
power band quicker, and to allow the engine to idle while still in gear. The
TCC "locks up" via this clutch while at highway speeds to reduce parasitic
losses through the slippage. Lockup is controlled via the PCM.
A hand-held scan tool most commonly used by GM technicians. They cost
upwards of $1000 each, but are very complete in their coverage of the LT1
engine parameters and have the capability to flash the PCM with a new program.
See also: PCM,
Acronym for Transmission Fluid Temperature. A sensor input used by the PCM
for unknown purposes, probably to control shift feel.
The throttle body is located on the front of the engine attached to the
intake manifold. Its job is to control air flow to the engine based on the
throttle position, which controls the speed of the engine. During idle, the
throttle body is almost closed and idle speed is controlled by the IAC valve.
See also: PCM,
Throttle Position Sensor
Provides a voltage to the PCM that changes in relationship to the throttle
blade opening or closing. This signal varies from about .6 volts as idle to
about 5 volts at WOT. The TPS is one of the most important sensors used by the
PCM for fuel control and most of the other PCM controlled outputs. See also:
Acronym for Throttle Position Sensor. See also: Throttle
Acronym for Twilight Sentinel. See also: Twilight
Acronym for Technical Service Bulletin. These are short papers distributed
to GM technician to help them diagnose and remedy common complaints and
problems. They are not the same as recalls, which are done at no cost to the
consumer and are usually only performed for safety reasons. TSBs are usually
covered under the original warranty, if it is still in effect.
The twilight sentinel uses a sensor near the defogger vent to detect
whether it is light or dark outside. If it is dark, it automatically turns the
headlights on. Similarly, if it is light, it turns them off. It also has a
feature that leaves the lights on for a specified period of time after the car
is shut off as a security measure. This option is incompatible with DRLs. See
Entrys for 'U'
Acronym for Underhood Electrical Center. This is a black box that is
located near the firewall on the passengers side. Inside the box you will find
various fuses and relays, and beside it you will find the auxiliary battery
Entrys for 'V'
Vehicle Speed Sensor
A permanent magnet generator located in the transmission. It transmits a
pulsing AC voltage in relation to the speed of the vehicle. The PCM converts
the pulsing frequency to a speed and sends it to the speedometer, odometer,
cruise control, chime module, and power steering control module. See also: PCM.
Acronym for the Vehicle Speed Sensor See also: Vehicle
Entrys for 'W'
Acronym for Wide Open Throttle. This occurs when the throttle is opened
more than about 75%. See also: Power
Entrys for 'Z'
Option code for the Camaro high performance package. Many of the parts
from the current generation of the Camaro Z28 will fit Impalas. See also: 1LE, SS.
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