Honda EP3 Service Manual page 252

lgnition Timing Control
The ECM contains the memory for basic ignition timing
at various engine speeds and manifold absolute
pressure. lt also adjusts the timing according to engine
coolant temperature.
Iniector Timing and Duration
The ECM contains the memory for basic discharge
d u r a t i o n a t v a r i o u s e n g i n e s p e e d s a n d m a n i f o l d
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
d i s c h a r g e d u r a t i o n .
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 temDerature increases.
Knock Sensor
The knock control system adjusts the ignition timing to
minimize knock.
PIEZO
CERAMIC
Malfunction Indicator Lamp lMlLl Indication {ln relation
to Readiness Codes)
The vehicle has certain
"readiness codes" that are part
of the on-board diagnostics for the emissions systems.
lf the vehicle's baftery has been disconnected or gone
dead. if the DTCS 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 comDlete. lf 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 (ll). but do not start the
e n g i n e . T h e M I L w i l l c o m e o n f o r l S 2 0 s e c o n d s . l f i t
then goes off, the readiness codes are set to complete,
lf it blinks severaltimes, one or more readiness codes
are not set to comolete. To set each code, drive the
v e h i c l e o r r u n t h e e n g i n e a s d e s c r i b e d i n t h e
procedures to set them in this section (see page 1 1-46).
Manifold Absolute Pressure {MAP) Senso]
The MAP sensor converts manifold absolute pressure
i n t o e l e c t r i c a l s i g n a l s t o t h e E C M .
SENSOR UNIT
( c o n t ' d )
11-27