Dodge Dakota (R1). Manual - part 569

in closed loop operation during periods of extended
idle.

In Closed Loop operation, the PCM monitors cer-

tain O2 sensor input(s) along with other inputs, and
adjusts the injector pulse width accordingly. During
Open Loop operation, the PCM ignores the O2 sensor
input. The PCM adjusts injector pulse width based
on preprogrammed (fixed) values and inputs from
other sensors.

Upstream Sensor - Engine Equipped With 2

Sensors: The upstream sensor (1/1) provides an
input voltage to the PCM. The input tells the PCM
the oxygen content of the exhaust gas. The PCM uses
this information to fine tune fuel delivery to main-
tain the correct oxygen content at the downstream
oxygen sensor. The PCM will change the air/fuel
ratio until the upstream sensor inputs a voltage that
the PCM has determined will make the downstream
sensor output (oxygen content) correct.

The upstream oxygen sensor also provides an input

to determine catalytic convertor efficiency.

Downstream Sensor - Engine Equipped With

2 Sensors: The downstream oxygen sensor (1/2) is
also used to determine the correct air-fuel ratio. As
the oxygen content changes at the downstream sen-
sor, the PCM calculates how much air-fuel ratio
change is required. The PCM then looks at the
upstream oxygen sensor voltage and changes fuel
delivery until the upstream sensor voltage changes
enough to correct the downstream sensor voltage
(oxygen content).

The downstream oxygen sensor also provides an

input to determine catalytic convertor efficiency.

Upstream Sensors - Engine Equipped With 4

Sensors: Two upstream sensors are used (1/1 and
2/1). The 1/1 sensor is the first sensor to receive

exhaust gases from the #1 cylinder. They provide an
input voltage to the PCM. The input tells the PCM
the oxygen content of the exhaust gas. The PCM uses
this information to fine tune fuel delivery to main-
tain the correct oxygen content at the downstream
oxygen sensors. The PCM will change the air/fuel
ratio until the upstream sensors input a voltage that
the PCM has determined will make the downstream
sensors output (oxygen content) correct.

The upstream oxygen sensors also provide an input

to determine mini-catalyst efficiency. Main catalytic
convertor efficiency is not calculated with this pack-
age.

Downstream Sensors - Engine Equipped With

4 Sensors: Two downstream sensors are used (1/2
and 2/2). The downstream sensors are used to deter-
mine the correct air-fuel ratio. As the oxygen content
changes at the downstream sensor, the PCM calcu-
lates how much air-fuel ratio change is required. The
PCM then looks at the upstream oxygen sensor volt-
age, and changes fuel delivery until the upstream
sensor voltage changes enough to correct the down-
stream sensor voltage (oxygen content).

The downstream oxygen sensors also provide an

input to determine mini-catalyst efficiency. Main cat-
alytic convertor efficiency is not calculated with this
package.

Engines equipped with either a downstream sen-

sor(s), or a post-catalytic sensor, will monitor cata-
lytic

convertor

efficiency.

efficiency

below

emission standards, the Malfunction Indicator Lamp
(MIL) will be illuminated and a Diagnostic Trouble
Code (DTC) will be set. Refer to Monitored Systems
in Emission Control Systems for additional informa-
tion.

14 - 48

FUEL INJECTION

O2 SENSOR (Continued)

REMOVAL - EXCEPT 2.5L

Never apply any type of grease to the oxygen

sensor electrical connector, or attempt any sol-
dering of the sensor wiring harness. For sensor
operation, it must have a comparison source of
oxygen from outside the exhaust system. This
fresh air is supplied to the sensor through its
pigtail wiring harness.

For sensor locations, refer to (Fig. 44), (Fig. 45),

(Fig. 46) (Fig. 47) or (Fig. 48).

WARNING: THE EXHAUST MANIFOLD, EXHAUST
PIPES

AND

CATALYTIC

CONVERTER

BECOME

VERY HOT DURING ENGINE OPERATION. ALLOW
ENGINE TO COOL BEFORE REMOVING OXYGEN
SENSOR.

Fig. 44 Upstream Oxygen Sensor Locations—

Except 4.7L V-8 Engine

1 - EXHAUST PIPE
2 - UPSTREAM OXYGEN SENSOR

Fig. 45 Downstream Oxygen Sensor Location—

Except 4.7L V-8 Engine

1 - DOWNSTREAM OXYGEN SENSOR
2 - FRAME RAIL
3 - CATALYTIC CONVERTER

Fig. 46 Pre-Catalyst/Post-Catalyst Oxygen Sensor

Locations—Except 4.7L V-8 Engine

1 - PRE-CATALYST OXYGEN SENSOR
2 - POST-CATALYST OXYGEN SENSOR

Fig. 47 Left/Right Oxygen Sensor Locations—

Except 4.7L V-8 Engine

1 - LEFT OXYGEN SENSOR
2 - RIGHT OXYGEN SENSOR

FUEL INJECTION

14 - 49

O2 SENSOR (Continued)

(1) Raise and support the vehicle.
(2) Disconnect the wire connector from the O2S

sensor.

CAUTION: When disconnecting the sensor electrical
connector, do not pull directly on wire going into
sensor.

(3) Remove the O2S sensor with an oxygen sensor

removal and installation tool.

Fig. 48 Oxygen Sensor Locations—4.7L V-8 Engine

14 - 50

FUEL INJECTION

O2 SENSOR (Continued)

REMOVAL - 2.5L

Never apply any type of grease to the oxygen

The upstream O2S sensor is located in the exhaust

downpipe. The downstream sensor is located near
outlet end of catalytic converter. Refer to (Fig. 49) or
(Fig. 50).

WARNING: THE EXHAUST MANIFOLD, EXHAUST
PIPES

AND

CATALYTIC

CONVERTER

BECOME

VERY HOT DURING ENGINE OPERATION. ALLOW
ENGINE TO COOL BEFORE REMOVING OXYGEN
SENSOR.

(1) Raise and support the vehicle.
(2) Disconnect the wire connector from the O2S

sensor.

CAUTION: When disconnecting the sensor electrical
connector, do not pull directly on wire going into
sensor.

(3) Remove the O2S sensor with an oxygen sensor

removal and installation tool.

INSTALLATION - EXCEPT 2.5L

Threads of new oxygen sensors are factory coated

with anti-seize compound to aid in removal. DO
NOT add any additional anti-seize compound to
the threads of a new oxygen sensor.

(1) Install the O2S sensor. Tighten to 30 N·m (22

ft. lbs.) torque.

(2) Connect the O2S sensor wire connector.
(3) Lower the vehicle.

INSTALLATION - 2.5L

Threads of new oxygen sensors are factory coated

with anti-seize compound to aid in removal. DO
NOT add any additional anti-seize compound to
the threads of a new oxygen sensor.

(1) Install the O2S sensor. Tighten to 30 N·m (22

ft. lbs.) torque.

(2) Connect the O2S sensor wire connector.
(3) Lower the vehicle.

THROTTLE BODY

DESCRIPTION

The throttle body is located on the intake manifold.

Fuel does not enter the intake manifold through the
throttle body. Fuel is sprayed into the manifold by
the fuel injectors.

OPERATION

Filtered air from the air cleaner enters the intake

manifold through the throttle body. The throttle body
contains an air control passage controlled by an Idle
Air Control (IAC) motor. The air control passage is
used to supply air for idle conditions. A throttle valve
(plate) is used to supply air for above idle conditions.

Certain sensors are attached to the throttle body.

The accelerator pedal cable, speed control cable and
transmission control cable (when equipped) are con-
nected to the throttle body linkage arm.

Fig. 49 Upstream Oxygen Sensor Location—2.5L

Engine

1 - UPSTREAM OXYGEN SENSOR
2 - EXHAUST PIPE

Fig. 50 Downtream Oxygen Sensor Location—2.5L

Engine

1 - DOWNSTREAM OXYGEN SENSOR
2 - FRAME RAIL
3 - CATALYTIC CONVERTER

FUEL INJECTION

14 - 51

O2 SENSOR (Continued)

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