User Manual

Glossary • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
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B
MAF:
Mass Air Flow Sensor. Measures the
amount and density of air entering the
engine and sends a frequency or voltage
signal to the PCM. The PCM uses this
signal in its fuel delivery calculations.
MAP:
Manifold Absolute Pressure Sensor.
Measures intake manifold vacuum or
pressure and sends a frequency or
voltage signal (depending on sensor type)
to the PCM. This gives the PCM
information on engine load for control of
fuel delivery, spark advance, and EGR
flow.
MAT:
Manifold Air Temperature sensor. A
resistance sensor in the intake manifold
that sends a voltage signal to the PCM
indicating the temperature of the
incoming air. The PCM uses this signal
for fuel delivery calculations.
MIL:
Malfunction Indicator Lamp. The MIL is
most commonly known as the “Check
Engine” or “Service Engine Soon” light. A
required on-board indicator to alert the
driver of an emission-related malfunction.
Monitor:
A test performed by the on-board
computer to verify proper operation of
emission related systems or components.
MPFI or MFI:
Multi-Port Fuel Injection. MPFI is a fuel
injection system using one (or more)
injector(s) for each cylinder. The injectors
are mounted in the intake manifold, and
fired in groups rather than individually.
NOx:
Oxides of Nitrogen. A pollutant. The EGR
system injects exhaust gases into the
intake manifold to reduce these gases at
the tailpipe.
O2S:
Oxygen Sensor. Generates a voltage of
0.6 to 1.1 volts when the exhaust gas is
rich (low oxygen content). The voltage
changes to 0.4 volts or less when the
exhaust gas is lean (high oxygen
content). This sensor only operates after
it reaches a temperature of approximately
349×C (660×F). O2 sensors are usually
found both upstream and downstream of
the catalytic converter. The PCM uses
these sensors to fine tune the air-fuel
ratio and to monitor the efficiency of the
catalytic converter. See Bank 1, Bank 2,
Sensor 1, Sensor 2.
OBD II:
On-Board Diagnostics, Second
Generation. OBD II is a U.S.
Government-mandated standard
requiring all cars and light trucks to have
a common data connector, connector
location, communication protocol, DTCs
and code definitions. OBD II first
appeared on vehicles in late 1994, and is
required to be present on all cars sold in
the US after January 1, 1996.
ODM:
Output Device Monitor.
Open Loop (OL):
A control system mode that does not
monitor the output to verify if the desired
results were achieved. A fuel delivery
system will usually operate in open loop
mode during cold engine warm-up
because the oxygen sensors are not yet
ready to send a signal. Without the
oxygen sensor signal, the computer
cannot check the actual results of
combustion.
PCM:
Powertrain Control Module. The “brains”
of the engine control system housed in a
metal box with a number of sensors and
actuators connected via a wiring harness.
Its job is to control fuel delivery, idle
speed, spark advance timing, and
emission systems. The PCM receives
information from sensors, then energizes
various actuators to control the engine.
The PCM is also known as the ECM
(Engine Control Module).
Pending Codes:
Also referred to as Continuous Memory
codes and Maturing Diagnostic Trouble
codes. These codes are set when
intermittent faults occur while driving. If
the fault does not occur after a certain
number of drive cycles, the code is
erased from memory.
PID:
Parameter Identification. Identifies an
address in memory which contains
vehicle operating information.