Saab 9000 Service Manual page 48

Fuel injection (contd.)
23
if
the engine is running on a rich mixture (Lambda be-
low 1 ), the output voltage of the sensor will be about
0.9 V.
If the engine is running on a lean mixture (Lambda
above 1 ), the output voltage of the sensor will be
0.1 V. The sensor output voltage changes very
quickly once Lambda exceeds 1.
The engine control module continuously corrects the
fuel injection time so that Lambda = 1 is always ob-
tained.
In order to produce a voltage as soon as possible af-
ter starting, the oxygen sensors must be preheated.
The preheating circuit is supplied with current ·(B+)
from the fuel pump relay via fuse 28 and grounded
via pin 50 of the engine control module. The engine
control module estimates the temperature of the ex-
haust gases on the basis of load and engine speed.
Preheating is disconnected at high exhaust gas tem-
peratures.
Closed loop is activated 640 engine revolutions after
starting if coolant temperature exceeds 17°C (63°F)
under partial load or 20°c (68° F) at idling speed.
592Fa
Note
Technical Description 45
H70·1
V
t--____; ___
..:;_•_---1
0.8
0.6
0.4
0.2
0
L------1-----1-.-..1,___J
0.80 0.90 1.00 1.10 1.20
'A
589
50
µp
µp
67
C\I
C\I
C\I
r-...
~
(0
-q-
C\I
(.)
The oxygen sensor before the three way catalytic
converter is called the front heated oxygen sensor
or "Oxygen sensor 1 ". The oxygen sensor after the
three way catalytic converter is called the rear
heated oxygen sensor or "Oxygen sensor 2".
Saab9000
I