Engine General Information and Diagnosis: 1A-12
A/F Sensor Description
S5JB0A1101012
A/F sensor (1), in place of the conventional heated Oxygen sensor-1, is installed in the center of the exhaust manifold
joining section and it consists of a zirconia element (2) which causes the output current to vary according to difference
in the oxygen concentration, a heater (3) which activates the element and an adjusting resistor (4) which adjusts
individual difference of the sensor.
A/F sensor detects oxygen concentration in exhaust gas (9) (A/F ratio of the air-fuel mixture) linearly, ranging from
LEAN to RICH.
Operation
ECM (5) controls the sensor heater (3) and keeps the sensor element temperature at the specified level (about 750
°
C) constantly so that the A/F sensor is activated in the specified way for accurate A/F detection. When the sensor
element reaches the specified temperature (it is activated), its impedance drops to the specified value (approx. 30
Ω
)
by its characteristic.
When a certain voltage (about 0.4 V) is applied between sensor elements in this state, circuit current corresponding to
the sensor element impedance flows in the sensor circuit. ECM detects this circuit current and judges whether the
sensor is in the active state or not. At this time, sensor current is output linearly in the range of +0.01 mA to +some mA
on the lean side and –0.01 mA to – some mA on the rich side. The variation in these ranges depends on the difference
from the stoichiometry A/F ratio, that is, the amount of oxygen between the atmosphere side (6) and exhaust manifold
(7).
According to this sensor output, ECM executes A/F feedback (fuel trim) to achieve the target A/F ratio.
The A/F sensor connector (8) is provided with an adjusting resistor (4) ECM detects the adjusting resistance value and
corrects the sensor output current value.
IG
L
C
FR
E
2
B
1
3
5
CMO
CMG
CMV
FCD
GCD
5V
11
10
9
8
7
4
6
I5JB0A110009-01
6. Ignition switch
8. Battery
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