Honda 2004 Odyssey Service Manual page 321

Fuel and Emissions Systems
System Descriptions (cont'd)
PCM Data (cont'd)
Data
Fuel System Fuel system status is indicated as ''open'' or ''closed''.
Status Closed: Based on the HO2S output, the PCM determines
the air/fuel ratio and controls the amount of injected
fuel.
Open: Ignoring HO2S output, the PCM refers to signals
from the Throttle Position (TP), Manifold Absolute
Pressure (MAP), Intake Air Temperature (IAT),
Barometric Pressure (BARO) and Engine Coolant
Temperature (ECT) sensors to control the amount of
injected fuel.
Short Term Fuel The air/fuel ratio correction coefficient for correcting
Trim the amount of injected fuel when the fuel system status
is ''closed''. When the ratio is leaner than the
stoichiometric ratio, the PCM increase short term fuel
trim gradually, and the amount of injected fuel
increases. The air/fuel ratio gradually gets richer,
causing a lower oxygen content in the exhaust gas.
Consequently, the short term fuel trim is lowered, and
the PCM reduces the amount of injected fuel. This cycle
keeps the air/fuel ratio close to the stoichiometric ratio
when in closed loop status.
Long Term Fuel Long term fuel trim is computed from short term fuel
Trim trim and indicates changes occurring in the fuel supply
system over a long period.
If long term fuel trim is higher than 1.00, the amount of
injected fuel must be increased. If it is lower than 1.00,
the amount of injected fuel must be reduced.
Intake Air The IAT sensor converts intake air temperature into
Temperature voltage and signals the PCM. When intake air
(IAT) temperature is low, the internal resistance of the sensor
increases, and the voltage signal is higher.
Throttle Position Based on the accelerator pedal position, the opening
angle of the throttle valve is indicated.
Ignition Timing Ignition timing is the ignition advance angle set by the
PCM. The PCM matches ignition timing to the driving
conditions.
Calculated Load CLV is the engine load calculated from the MAP data.
Value (CLV)
11-12
Description Operating Value
At idle speed: closed
0.6 1.5
0.8 1.2
With cold engine:
Same as ambient
temperature and ECT
At idle speed:
about 10 %, 0.5 V
At idle speed:
10° 2° BTDC when the
SCS service signal line
is jumped with the HDS
At idle speed:
16 33 %
At 2,500 rpm with no
load:
18 26 %
Freeze Data
YES
YES
YES
YES
YES
NO
YES