Loop status is indicated as
"open" or "closed"'
Closed: Based on the HO2S output, the ECM/PCM deter-
mines the airlfuel ratio and controls the amount of inject-
Open: lgnoring HO2S output, the ECM/PCM refers to sig-
nals from the TP, MAP, and ECT sensors to control the
amount of injected fuel.
The air/fuel ratio correction coefficient for correcting the
amount ot injected fuel when H02S feedback is in the
closed loop status When the signal from the HO2S is
weak, short term fuel trim gets higher, and the ECM/PCM
increases the amount of injected fuel The airlfuel ratio
gradually gets richer, causing a higher HO2S output
Consequently, the short term fuel trim is lowered, and
the ECMiPCM reduces the amount of injected fuel
This cvcle keeps the airlfuel ratio close to the stoichio-
metric ratio when in closed loop status'
F eeza Data
At idle speed: closed
Long term fuel trim is computed from shon term fuel
trim and indicates changes occurring in the fuel supply
svstem over a long Period
lf long term fuel trim is higher than 1.00, the amount of
injecGd fuel must be increased. lf it is lower than 1 00'
the amount of injected fuel must be reduced'
The IAT sensor converts intake air temperature into volt-
age and signals the ECM/PCM. When intake air tempera-
ture is low, the internal resistance of the sensor
increases. and the voltaqe signal is higher'
With cold engine:
Same as ambient temPer'
ature and ECT
At idle speed:
approx. 10 %
Based on the accelerator pedal position, the open'ng
angle of the throttle valve is indicated
lgnition timing is the ignition advance angle set by the
gCV/eCV. tn" gCU/PCM matches ignition timing to the
CLV is the engine load calculated from the MAP data'
At idle speed: 12'i 2'
(81642 engine: 16" t 2")
BTDC with the SCS ser-
vice connector connected.
At idle speed:
1 5 - 3 5 %
At 2.500 rpm with no load:
12 - 30%