Mazda B-Series 1997 Workshop Manual page 373

OUTLINE
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COMPONENT
1
FUNCTION
1
REMARK
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ldle air control (IAC)
solenoid
Controls idle speed and provides a dashpot
function.
PCM uses IAC to control the following:
1. No touch start
2. Cold engine fast idle
3. ldle (corrects for engine load)
4. Provides a dashpot function
IAC solenoid is duty-controlled solenoid.
IAC is not adjustable and cannot be cleaned.
Ignition coil A coil in a coil pack is turned on by PCM,
then turned off, firing two spark plugs at once.
Spark plugs are paired so that as one spark plug
fires on the compression stroke, the other spark
plug fires on the exhaust stroke.
- -
-
IDM circuit is enclosed in PCM.
1
Inertia fuel shutoff
(IFS) switch
- - - -
Ignition diagnostic
IDM signal communicates informat~on by
monitor signal (IDM)
1
pulse width modulation.
Injector
Intake air temperature
(IAT) sensor
IFS is used in conjunction with fuel pump
and is used to shut off fuel pump if a collision
occurs.
Once switch is open, it must be manually
reset before restarting vehicle.
Amount of fuel is controlled by length of time
injector is held open. lnjector is operated by
12 volts from PCM power relay and ground
signal is controlled by PCM.
IFS consists of a steel ball held in place by a
magnet. When sharp impact occurs, ball breaks
loose from magnet, rolls up a conical ramp and
strikes a target plate which opens electrical
contacts and shuts off fuel pump.
Fuel injector is a normally closed and solenoid-
operated valve that meters fuel flow to engine.
If injector has been replaced, it is necessary to
clear learned values contained in Keep Alive
Memory in PCM by disconnecting battery or PCM
for five minutes.
Detects intake air temperature.
Sensor has the same function as ECT.
PCM uses IAT signals as correction factors
in calculation of fuel, spark and MAF.
Uses thermistor devices.
Resistance changes with temperature:
Resistance decreases as temperature
increases.
Resistance increases as temperature
decreases.
Sensor is connected to voltage divider so that
varying resistance of sensor causes a variation in
total current flow. Dropped voltage across a fixed
resistor in a series with sensor determines voltage
signal at PCM.
Keep alive memory
(KAM)
Malfunction indicator
lamp (MIL)
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1
Intake manifold
i
Supplies intake air to all cylinders.
PCM stores data in KAM about vehicle
operating conditions, and then uses data to
compensate for component variability.
Alerts driver to an OBD II emission-related
component or system malfunction.
MIL comes on in runlcrank mode as a bulb
check until PIP signal detected.
MIL should turn off after PIP signal detected.
MIL remains on in the following conditions:
A short to ground of MIL circuit
Operation in HLOS
When vehicle was last shut down
After DTC is stored in memory
MIL blinks in the following procedures:
A severe misfire is detected
Intermittent in MIL circuit
1
KAM remains powered when ignition is off so
that information is not lost until PCM connector
disconnected or battery cable disconnected.
If OBD II related component or system is
malfunctioning, OBD II DTC will be set.
To extinguish MIL after repair, a reset command
from scan tool or NGS must be sent, or three
consecutive drive cycles must be completed
without a malfunction.
Mass air flow (MAF) Detects intake air mass.
sensor
I
Outputs analog voltage signal to PCM.
PCM controls operation as follows:
1. Required fuel injector pulse width
2. EPC
3. ShiWtorque converter clutch scheduling
Octane adjust
(OCT ADJ) shorting
1
bar
OCT ADJ shorting bar is used to retard
spark three degrees when bar is removed
from in-line connector.
Uses a hot wire sending element to measure
intake air mass. Hot wire is maintained at 200°C
(392°F)
above ambient temperature as measured
by a constant cold wire. Air passing hot wire
causes it to cool. The current required to maintain
hot wire temperature is proportional to air mass
flow. MAF then outputs signal to PCM.
OCT ADJ self test is to check state of OCT ADJ
shorting bar. DTC will be present if bar is removed
or if there is an oDen circuit.