Dodge Durango (HB). Manual — part 246

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When engine has reached operating temperature, the PCM will begin monitoring O2S sensor input. The sys-
tem will then leave the warm-up mode and go into closed loop operation.

IDLE MODE

When the engine is at operating temperature, this is a Closed Loop mode. At idle speed, the PCM receives inputs
from:

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Air conditioning select signal (if equipped)

•

Air conditioning request signal (if equipped)

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Battery voltage

•

Crankshaft position sensor

•

Engine coolant temperature sensor

•

Intake manifold air temperature sensor

•

Manifold absolute pressure (MAP) sensor

•

Throttle position sensor (TPS)

•

Camshaft position sensor signal

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Battery voltage

•

Park/neutral switch (gear indicator signal—auto. trans. only)

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Oxygen sensors

Based on these inputs, the following occurs:

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Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control injection
sequence and injector pulse width by turning the ground circuit to each individual injector on and off.

•

The PCM monitors the O2S sensor input and adjusts air-fuel ratio by varying injector pulse width. It also
adjusts engine idle speed through the idle air control (IAC) motor.

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The PCM adjusts ignition timing by increasing and decreasing spark advance.

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The PCM operates the A/C compressor clutch through the clutch relay. This happens if A/C has been selected
by the vehicle operator and requested by the A/C thermostat.

CRUISE MODE

When the engine is at operating temperature, this is a Closed Loop mode. At cruising speed, the PCM receives
inputs from:

•

Air conditioning select signal (if equipped)

•

Air conditioning request signal (if equipped)

•

Battery voltage

•

Engine coolant temperature sensor

•

Crankshaft position sensor

•

Intake manifold air temperature sensor

•

Manifold absolute pressure (MAP) sensor

•

Throttle position sensor (TPS)

•

Camshaft position sensor signal

•

Park/neutral switch (gear indicator signal—auto. trans. only)

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Oxygen (O2S) sensors

Based on these inputs, the following occurs:

•

Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then adjust the injector
pulse width by turning the ground circuit to each individual injector on and off.

•

The PCM monitors the O2S sensor input and adjusts air-fuel ratio. It also adjusts engine idle speed through
the idle air control (IAC) motor.

•

The PCM adjusts ignition timing by turning the ground path to the coil on and off.

•

The PCM operates the A/C compressor clutch through the clutch relay. This happens if A/C has been selected
by the vehicle operator and requested by the A/C thermostat.

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ACCELERATION MODE

This is an Open Loop mode. The PCM recognizes an abrupt increase in throttle position or MAP pressure as a
demand for increased engine output and vehicle acceleration. The PCM increases injector pulse width in response
to increased throttle opening.

DECELERATION MODE

When the engine is at operating temperature, this is an Open Loop mode. During hard deceleration, the PCM
receives the following inputs.

•

Air conditioning select signal (if equipped)

•

Air conditioning request signal (if equipped)

•

Battery voltage

•

Engine coolant temperature sensor

•

Crankshaft position sensor

•

Intake manifold air temperature sensor

•

Manifold absolute pressure (MAP) sensor

•

Throttle position sensor (TPS)

•

Camshaft position sensor signal

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Park/neutral switch (gear indicator signal—auto. trans. only)

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Vehicle speed sensor

If the vehicle is under hard deceleration with the proper rpm and closed throttle conditions, the PCM will ignore the
oxygen sensor input signal. The PCM will enter a fuel cut-off strategy in which it will not supply a ground to the
injectors. If a hard deceleration does not exist, the PCM will determine the proper injector pulse width and continue
injection.

Based on the above inputs, the PCM will adjust engine idle speed through the idle air control (IAC) motor.

The PCM adjusts ignition timing by turning the ground path to the coil on and off.

WIDE OPEN THROTTLE MODE

This is an Open Loop mode. During wide open throttle operation, the PCM receives the following inputs.

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Battery voltage

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Crankshaft position sensor

•

Engine coolant temperature sensor

•

Intake manifold air temperature sensor

•

Manifold absolute pressure (MAP) sensor

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Throttle position sensor (TPS)

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Camshaft position sensor signal

During wide open throttle conditions, the following occurs:

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Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection
sequence and injector pulse width by turning the ground circuit to each individual injector on and off. The PCM
ignores the oxygen sensor input signal and provides a predetermined amount of additional fuel. This is done
by adjusting injector pulse width.

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The PCM adjusts ignition timing by turning the ground path to the coil on and off.

IGNITION SWITCH OFF MODE

When ignition switch is turned to OFF position, the PCM stops operating the injectors, ignition coil, ASD relay and
fuel pump relay.

5 VOLT SUPPLIES

Two different Powertrain Control Module (PCM) five volt supply circuits are used; primary and secondary.

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IGNITION CIRCUIT SENSE

This circuit ties the ignition switch to the Powertrain Control Module (PCM). Battery voltage is supplied to the PCM
through the ignition switch when the ignition is in the Run or Start position. This is referred to as the “ignition sense”
circuit and is used to “wake up” the PCM.

POWER GROUNDS

The Powertrain Control Module (PCM) has 2 main grounds. Both of these grounds are referred to as power
grounds. All of the high-current, noisy, electrical devices are connected to these grounds as well as all of the sensor
returns. The sensor return comes into the sensor return circuit, passes through noise suppression, and is then con-
nected to the power ground.

The power ground is used to control ground circuits for the following PCM loads:

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Generator field winding

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Fuel injectors

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Ignition coil(s)

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Certain relays/solenoids

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Certain sensors

SENSOR RETURN

The Sensor Return circuits are internal to the Powertrain Control Module (PCM).

Sensor Return provides a low–noise ground reference for all engine control system sensors. Refer to Power
Grounds for more information.

SIGNAL GROUND

Signal ground provides a low noise ground to the data link connector.

OPERATION

POWERTRAIN CONTROL MODULE (PCM)

The PCM is a pre-programmed, microprocessor digital computer. It regulates ignition timing, air-fuel ratio, emission
control devices, charging system, certain transmission features, speed control, air conditioning compressor clutch
engagement and idle speed. The PCM can adapt its programming to meet changing operating conditions.

The PCM receives input signals from various switches and sensors. Based on these inputs, the PCM regulates
various engine and vehicle operations through different system components. These components are referred to as
Powertrain Control Module (PCM) Outputs. The sensors and switches that provide inputs to the PCM are consid-
ered Powertrain Control Module (PCM) Inputs.

The PCM adjusts ignition timing based upon inputs it receives from sensors that react to: engine rpm, manifold
absolute pressure, engine coolant temperature, throttle position, transmission gear selection (automatic transmis-
sion), vehicle speed and the brake switch.

The PCM adjusts idle speed based on inputs it receives from sensors that react to: throttle position, vehicle speed,
transmission gear selection, engine coolant temperature and from inputs it receives from the air conditioning clutch
switch and brake switch.

Based on inputs that it receives, the PCM adjusts ignition coil dwell. The PCM also adjusts the generator charge
rate through control of the generator field and provides speed control operation.

NOTE: PCM Inputs:

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Accelerator pedal position sensor (if equipped)

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A/C request (if equipped with factory A/C)

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A/C select (if equipped with factory A/C)

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Auto shutdown (ASD) sense

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Battery temperature

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Battery voltage

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Brake switch

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CAN bus (+) circuits

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CAN bus (-) circuits

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Camshaft position sensor signal

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Clutch Interlock Switch (if equipped)

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Crankshaft position sensor

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Data link connection for diagnostic scan tool

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EGR position sensor (if equipped)

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Engine coolant temperature sensor

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Fuel level

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Generator (battery voltage) output

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Ignition circuit sense (ignition switch in on/off/crank/run position)

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Intake manifold air temperature sensor

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Knock sensor(s) (if equipped)

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Leak detection pump (switch) sense (if equipped)

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Manifold absolute pressure (MAP) sensor

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Oil pressure sensor

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Output shaft speed sensor

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Overdrive/override switch

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Oxygen sensors

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Park/neutral switch (auto. trans. only)

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Power ground

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Power steering pressure switch (if equipped)

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Sensor return

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Signal ground

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Speed control multiplexed single wire input

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Throttle position sensor

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Transmission governor pressure sensor

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Transmission output speed sensor

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Transmission temperature sensor

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Vehicle speed inputs from ABS or RWAL system

NOTE: PCM Outputs:

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A/C clutch relay

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Auto shutdown (ASD) relay

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CAN bus (+/-) circuits for: speedometer, voltmeter, fuel gauge, oil pressure gauge/lamp, engine temp. gauge
and speed control warn. lamp

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Data link connection for diagnostic scan tool

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Double start override (if equipped)

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EGR valve control solenoid (if equipped)

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Electronic throttle control

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EVAP canister purge solenoid

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Five volt sensor supply (primary)

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Five volt sensor supply (secondary)

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Fuel injectors

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Fuel pump relay

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Generator field driver (-)

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Generator field driver (+)

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Generator lamp (if equipped)

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Idle air control (IAC) motor

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Ignition coil(s)

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