Dodge ram truck 3500 1996 Service Manual page 1267

BR
FUEL SYSTEM 14 - 33
D E S C R I P T I O N A N D O P E R A T I O N (Continued)
DOWN STREAM
OXYGEN
SENSOR
UP STREAM
OXYGEN
SENSOR
Fig. 9 Upstream/Downstream Oxygen Sensors—
LDC Engines
HEATED OXYGEN SENSOR (02S)—HDC
ENGINES—PCM INPUT
A total of two heated 02S sensors are used (left
and right) on HDC engines. On the 5.9L HDC
engine, the left 02S sensor will monitor cylinders 1,
3, 5 and 7. The right sensor will monitor cylinders 2,
4, 6 and 8. On the 8.0L V-10 HDC engine, the left
02S sensor will monitor cylinders 1, 3, 5, 7 and 9.
The right sensor will monitor cylinders 2, 4, 6, 8 and
10.
The sensors produce voltages from 0 to 1 volt,
depending upon the oxygen content of the exhaust
gas in the exhaust manifold. When a large amount of
oxygen is present (caused by a lean air/fuel mixture),
the sensors produces a low voltage. When there is a
lesser amount present (rich air/fuel mixture) It pro­
duces a higher voltage. By monitoring the oxygen
content and converting It to electrical voltage, the
sensors act as a rich-lean switch.
The oxygen sensors are equipped with a heating
element that keeps the sensors at proper operating
temperature during all operating modes. Maintaining
correct sensor temperature at all times allows the
system to enter into closed loop operation sooner.
Also, it allows the system to remain In closed loop
operation during periods of extended Idle.
In Closed Loop operation, the PCM monitors the
02S sensor Input (along with other inputs) and
adjusts the Injector pulse width accordingly. During
Open Loop operation, the PCM ignores the 02 sensor
input. The PCM adjusts Injector pulse width based
on preprogrammed (fixed) values and inputs from
other sensors.
The Automatic Shutdown (ASD) relay supplies bat­
tery voltage to both oxygen sensors. The oxygen sen­
sors are equipped with a heating elements. The
heating elements reduce the time required for the
sensors to reach operating temperature.
Pig. 10 Left/Right Heated Oxygen Sensors—HDC
Engines
HEATED OXYGEN SENSOR (02S)—8.0L I D C
ENGINES—PCM INPUT
The 8.0L V-10 engine, when equipped with a
Medium Duty Emission Cycle (MDC) package, will
use four heated 02S sensors. They are: Left, right,
pre-catalyst and post catalyst. The left, right and
post catalyst sensors will fine-tune air-fuel ratio. The
pre-catalyst and post catalyst sensors will determine
catalytic converter efficiency.
Two of these sensors are installed into the left and
right exhaust manifold downpipes (Fig. 10). On the
8.0L V-10 MDC engine, the left 02S sensor will mon­
itor cylinders 1, 3, 5, 7 and 9. The right sensor will
monitor cylinders 2, 4, 6, 8 and 10.
The sensors produce voltages from 0 to 1 volt,
depending upon the oxygen content of the exhaust
gas in the exhaust manifold. When a large amount of
oxygen is present (caused by a lean air/fuel mixture),
the sensors produces a low voltage. When there is a
lesser amount present (rich air/fuel mixture) i t pro­
duces a higher voltage. By monitoring the oxygen
content and converting i t to electrical voltage, the
sensors act as a rich-lean switch.
The oxygen sensors are equipped with a heating
element that keeps the sensors at proper operating
temperature during all operating modes. Maintaining
correct sensor temperature at all times allows the
system to enter into closed loop operation sooner.
Also, it allows the system to remain i n closed loop
operation during periods of extended idle.
In Closed Loop operation, the PCM monitors the
02S sensor input (along with other inputs) and
adjusts the injector pulse width accordingly. During
Open Loop operation, the PCM ignores the 02 sensor
input. The PCM adjusts injector pulse width based
on preprogrammed (fixed) values and inputs from
other sensors.