Ignition Timing Control; Injector Timing And Duration; Intake Air Temperature (Lat) Sensor; Manifold Absolute Pressure (Map) Sensor - Honda Civic 2002-2003 Service Manual

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Ignition Timing Control
The ECM contains the memory for basic ignition timing
at various engine speeds and manifold absolute
pressure. It also adjusts the timing according to engine
coolant temperature.
Injector Timing and Duration
The ECM contains the memory for basic discharge
duration at various engine speeds and manifold
pressures. The basic discharge duration, after being
read out from the memory, is further modified by
signals sent from various sensors to obtain the final
discharge duration.
By monitoring long term fuel trim, the ECM detects long
term malfunctions in the fuel system and sets a
Diagnostic Trouble Code (DTC).
Intake Air Temperature (lAT) Sensor
The IAT sensor is a temperature dependent resistor
(thermistor). The resistance of the thermistor decreases
as the intake air temperature increases.
TERMINAL
THERMISTOR
Knock Sensor
The knock control system adjusts the ignition timing to
minimize knock.
TERMINAL
PIEZO
CERAMIC
Malfunction Indicator Lamp IMIL) Indication (In relation
to Readiness Codes)
The vehicle has certain "readiness codes" that are part
of the on-board diagnostics for the emissions systems.
lithe vehicle's battery has been disconnected or gone
dead, if the DTes have been cleared, or if the ECM has
been reset, these codes are set to incomplete. In some
states, part of the emissions testing is to make sure
these codes are set to complete. II all of them are not
set to complete, the vehicle may fail the test and the
test cannot be finished.
To check if the readiness codes are set to complete,
turn the ignition switch ON (II), but do not start the
engine. The MIL will come on for 15-20 seconds. II it
then goes off, the readiness codes are set to complete.
If it blinks several times, one or more readiness codes
are not set to complete. To set each code, drive the
vehicle or run the engine as described in the
procedures to set them in this section (see page 11-46).
Manifold Absolute Pressure (MAP) Sensor
The MAP sensor converts manifold absolute pressure
into electrical signals to the ECM.
SENSOR UNIT
Icont'd)
11-27