Honda Civic 2002-2003 Service Manual page 221

Fuel and Emissions Systems
System Descriptions (cont'd)
ECM Data (cont'd)
Data DescriPtion
OperatinllValue
Freeze Data
Fuel System Fuel system status is indicated as "open" or "closed". At idle speed: closed
I
YES
Status Closed: Based on the NF Sensor output, the ECM
determines the air/fuel ratio and controls the amount of
injected fuel.
Open: Ignoring NF Sensor output, the ECM refers to
signals from the throttle position (TP), manifold absolute
pressure (MAP), intake air temperature (lAT), barometric
pressure (BARD), and engine coolant temperature (ECT))
sensors to control the amount of iniected fuel.
Short Term The air/fuel ratio correction coefficient for correcting the ' 0.7-1.5 YES
Fuel Trim amount of injected fuel when the fuel system status
is "closed." When the ratio is leaner than the
,
stoichiometric ratio, the ECM increases 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 ECM reduces the
amount of injected fuel.
,
, This cycle keeps the air/fuel ratio close to the
stoichiometric ratio when in ctosed loop status.
Long Term Long term fuel trim is computed from short term fuel trim 0.8-1.2 YES
Fuel 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
With cold engine: YES
Temperature
voltage and signals the ECM. When intake air
Same as ambient
(IAT)
temperature is low, the internal resistance ofthe sensor temperature and ECT
increases, and the voltage signal is higher.
-
Throttle Based on the accelerator pedal position, the opening At idle speed: YES
Position
angle of the throttle valve is indicated.
about10%
Ignition Ignition timing is the ignition advance angle set by the At idle speed: 8'
±
5' ND
Timing ECM. The ECM matches ignition timing to driving BTDC when the SCS
conditions. service
signal line
is
jumped with the Honda I
PGM Tester c;:--
Calculated . CLV is the engine load calculated from MAP data.
At idle speed:
is
Load Value ' 12-34%
(CLV) . At 2,500 rpm with no
load: ,
14--34%
11-14