Honda 2004 Odyssey Service Manual page 354

PGM-FI System
The Programmed Fuel Injection (PGM-FI) system is a
sequential multiport fuel injection system.
A/C Compressor Clutch Relay
When the PCM receives a demand for cooling from the
A/C system, it delays compressor engagement, and
enriches the mixture to assure smooth transition to the
A/C mode.
A/C Switch
The A/C (air conditioning) switch signals the PCM
whenever there is a demand for cooling.
Alternator Control
The alternator signals the PCM during charging. The
PCM then controls the voltage generated by the
alternator according to the electrical load determined
by the Electrical Load Detector (ELD) and driving mode.
This reduces engine load to improve fuel economy.
Barometric Pressure (BARO) Sensor
The BARO sensor is inside the PCM. It converts
atmospheric pressure into a voltage signal that
modifies the basic duration of the fuel injection
discharge.
Camshaft Position (CMP) (Top Dead Center (TDC))
Sensor
The CMP (TDC) A/B sensor input is used by the PCM to
determine ignition timing at start up (cranking) and
when crank angle is abnormal.
CMP (TDC) SENSOR A
CMP (TDC) SENSOR B
Crankshaft Position (CKP) Sensor
The CKP sensor input is used by the PCM determine
timing for fuel injection of each cylinder and to detect
engine speed.
CKP SENSOR
Engine Coolant Temperature (ECT) Sensor
The ECT sensor is a temperature dependent resistor
(thermistor). The resistance of the thermistor decreases
as the engine coolant temperature increases.
Ignition Timing Control
The PCM 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 PCM 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 PCM detects
long term malfunctions in the fuel system, and sets a
diagnostic trouble code (DTC).
THERMISTOR
(cont'd)
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