Subaru 2002 Impreza Service Manual page 35

SENSORS AND SWITCHES
Fuel lniection (Fuel System)
0 s
s o
C L
.-
p z
- s
E %
g z %
2
5 s
- x o
w o >
Small
0
When rich air-fuel mixture is burnt in the cylinder, the oxygen in the exhaust gases is almost com-
pletely used in the catalytic reaction by the platinum coating on the external surface of the zirconia
tube. This results in a very large difference in the oxygen ion concentration between the inside and
outside of the tube, and the electromotive force generated is large.
0
When a lean air-fuel mixture is burnt in the cylinder, relatively large amount of oxygen remains
in the exhaust gases even after the catalytic action, and this results in a small difference in the oxy-
gen ion concentration between the tube's internal and external surfaces. The electromotive force
in this case is very small.
as rich
Comparison
t
voltage
-
- ~ -
4
To be judged
C: ENGINE COOLANT TEMPERATURE SENSOR
The engine coolant temperature sensor is located on the engine coolant pipe. The sensor uses
a thermistor whose resistance changes inversely with temperature. Resistance signals as engine
coolant temperature information are transmitted to the ECM to make fuel injection, ignition timing,
purge control solenoid valve and other controls.
A
Temp. "C ( O F )
1
-20 0 20 40 60 80
(-4) (32) (68) (104)(140)(176)
(1)
Connector
S2H1113B
(2) Thermistor element
FU-19