Chrysler 300/300 Touring/300C, Dodge Magnum. Manual — part 1774
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Idle
•
Acceleration
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Deceleration
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Wide Open Throttle
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Ignition switch OFF
5. The engine start-up (crank), engine warm-up, deceleration with fuel shutoff and wide open throttle modes are
OPEN LOOP modes. Under most operating conditions, the acceleration, deceleration (with A/C on), idle and
cruise modes, with the engine at operating temperature are CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the ignition switch activates the fuel injection system, the following actions occur:
•
The PCM monitors the engine coolant temperature sensor and throttle position sensor input. The PCM deter-
mines basic fuel injector pulse width from this input.
•
The PCM determines atmospheric air pressure from the MAP sensor input to modify injector pulse width.
When the key is in the ON position and the engine is not running (zero rpm), the Auto Shutdown (ASD) and fuel
pump relays de-energize after approximately 1 second. Therefore, battery voltage is not supplied to the fuel pump,
ignition coil, fuel injectors and heated oxygen sensors.
ENGINE START-UP MODE
This is an OPEN LOOP mode. If the vehicle is in park or neutral (automatic transaxles) or the clutch pedal is
depressed (manual transaxles) the ignition switch energizes the starter relay when the engine is not running. The
following actions occur when the starter motor is engaged.
•
If the PCM receives the camshaft position sensor and crankshaft position sensor signals, it energizes the Auto
Shutdown (ASD) relay and fuel pump relay. If the PCM does not receive both signals within approximately one
second, it will not energize the ASD relay and fuel pump relay. The ASD and fuel pump relays supply battery
voltage to the fuel pump, fuel injectors, ignition coil, (EGR solenoid and PCV heater if equipped) and heated
oxygen sensors.
•
The PCM energizes the injectors (on the 69° degree falling edge) for a calculated pulse width until it deter-
mines crankshaft position from the camshaft position sensor and crankshaft position sensor signals. The PCM
determines crankshaft position within 1 engine revolution.
•
After determining crankshaft position, the PCM begins energizing the injectors in sequence. It adjusts injector
pulse width and controls injector synchronization by turning the individual ground paths to the injectors On and
Off.
•
When the engine idles within ±64 RPM of its target RPM, the PCM compares current MAP sensor value with
the atmospheric pressure value received during the Ignition Switch On (zero RPM) mode.
Once the ASD and fuel pump relays have been energized, the PCM determines injector pulse width based on the
following:
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MAP
•
Engine RPM
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Battery voltage
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Engine coolant temperature
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Inlet/Intake air temperature (IAT)
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Throttle position
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The number of engine revolutions since cranking was initiated
During Start-up the PCM maintains ignition timing at 9° BTDC.
ENGINE WARM-UP MODE
This is an OPEN LOOP mode. The following inputs are received by the PCM:
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Manifold Absolute Pressure (MAP)
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Crankshaft position (engine speed)
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Engine coolant temperature
•
Inlet/Intake air temperature (IAT)
•
Camshaft position
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FUEL INJECTION
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Knock sensor
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Throttle position
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A/C switch status
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Battery voltage
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Vehicle speed
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Speed control
•
O2 sensors
The PCM adjusts injector pulse width and controls injector synchronization by turning the individual ground paths to
the injectors On and Off.
The PCM adjusts ignition timing and engine idle speed. Engine idle speed is adjusted through the idle air control
motor.
CRUISE OR IDLE MODE
When the engine is at operating temperature this is a CLOSED LOOP mode. During cruising or idle the following
inputs are received by the PCM:
•
Manifold absolute pressure
•
Crankshaft position (engine speed)
•
Inlet/Intake air temperature
•
Engine coolant temperature
•
Camshaft position
•
Knock sensor
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Throttle position
•
Exhaust gas oxygen content (O2 sensors)
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A/C switch status
•
Battery voltage
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Vehicle speed
The PCM adjusts injector pulse width and controls injector synchronization by turning the individual ground paths to
the injectors On and Off.
The PCM adjusts engine idle speed and ignition timing. The PCM adjusts the air/fuel ratio according to the oxygen
content in the exhaust gas (measured by the upstream and downstream heated oxygen sensor).
The PCM monitors for engine misfire. During active misfire and depending on the severity, the PCM either contin-
uously illuminates or flashes the malfunction indicator lamp (Check Engine light on instrument panel). Also, the PCM
stores an engine misfire DTC in memory, if 2nd trip with fault.
The PCM performs several diagnostic routines. They include:
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Oxygen sensor monitor
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Downstream heated oxygen sensor diagnostics during open loop operation (except for shorted)
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Fuel system monitor
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EGR monitor (if equipped)
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Purge system monitor
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Catalyst efficiency monitor
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All inputs monitored for proper voltage range, rationality.
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All monitored components (refer to the Emission section for On-Board Diagnostics).
The PCM compares the upstream and downstream heated oxygen sensor inputs to measure catalytic convertor
efficiency. If the catalyst efficiency drops below the minimum acceptable percentage, the PCM stores a diagnostic
trouble code in memory, after 2 trips.
During certain idle conditions, the PCM may enter a variable idle speed strategy. During variable idle speed strategy
the PCM adjusts engine speed based on the following inputs.
•
A/C status
•
Battery voltage
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Battery temperature or Calculated Battery Temperature
•
Engine coolant temperature
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FUEL INJECTION
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Engine run time
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Inlet/Intake air temperature
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Vehicle mileage
ACCELERATION MODE
This is a CLOSED LOOP mode. The PCM recognizes an abrupt increase in Throttle Position sensor output voltage
or MAP sensor output voltage as a demand for increased engine output and vehicle acceleration. The PCM
increases injector pulse width in response to increased fuel demand.
•
Wide Open Throttle-open loop
DECELERATION MODE
This is a CLOSED LOOP mode. During deceleration the following inputs are received by the PCM:
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A/C status
•
Battery voltage
•
Inlet/Intake air temperature
•
Engine coolant temperature
•
Crankshaft position (engine speed)
•
Exhaust gas oxygen content (upstream heated oxygen sensor)
•
Knock sensor
•
Manifold absolute pressure
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Throttle position sensor
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IAC motor (solenoid) control changes in response to MAP sensor feedback
The PCM may receive a closed throttle input from the Throttle Position Sensor (TPS) when it senses an abrupt
decrease in manifold pressure. This indicates a hard deceleration (Open Loop). In response, the PCM may momen-
tarily turn off the injectors. This helps improve fuel economy, emissions and engine braking.
WIDE-OPEN-THROTTLE MODE
This is an OPEN LOOP mode. During wide-open-throttle operation, the following inputs are used by the PCM:
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Inlet/Intake air temperature
•
Engine coolant temperature
•
Engine speed
•
Knock sensor
•
Manifold absolute pressure
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Throttle position
When the PCM senses a wide-open-throttle condition through the Throttle Position Sensor (TPS) it de-energizes the
A/C compressor clutch relay. This disables the air conditioning system and disables EGR (if equipped).
The PCM adjusts injector pulse width to supply a predetermined amount of additional fuel, based on MAP and RPM.
IGNITION SWITCH OFF MODE
When the operator turns the ignition switch to the OFF position, the following occurs:
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All outputs are turned off, unless 02 Heater Monitor test is being run. Refer to the Emission section for On-
Board Diagnostics.
•
No inputs are monitored except for the heated oxygen sensors. The PCM monitors the heating elements in the
oxygen sensors and then shuts down.
FUEL CORRECTION or ADAPTIVE MEMORIES
DESCRIPTION
In Open Loop, the PCM changes pulse width without feedback from the O2 Sensors. Once the engine warms up to
approximately 30 to 35° F, the PCM goes into closed loop Short Term Correction and utilizes feedback from the
O2 Sensors. Closed loop Long Term Adaptive Memory is maintained above 170° to 190° F unless the PCM
senses wide open throttle. At that time the PCM returns to Open Loop operation.
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FUEL INJECTION
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OPERATION
Short Term
The first fuel correction program that begins functioning is the short term fuel correction. This system corrects fuel
delivery in direct proportion to the readings from the Upstream O2 Sensor.
The PCM monitors the air/fuel ratio by using the input voltage from the O2 Sensor. When the voltage reaches its
preset high or low limit, the PCM begins to add or remove fuel until the sensor reaches its switch point. The short
term corrections then begin.
The PCM makes a series of quick changes in the injector pulse-width until the O2 Sensor reaches its opposite
preset limit or switch point. The process then repeats itself in the opposite direction.
Short term fuel correction will keep increasing or decreasing injector pulse-width based upon the upstream O2 Sen-
sor input. The maximum range of authority for short term memory is 25% (+/-) of base pulse-width. Short term is
violated and is lost when ignition is turned OFF.
Long Term
The second fuel correction program is the long term adaptive memory. In order to maintain correct emission
throughout all operating ranges of the engine, a cell structure based on engine rpm and load (MAP) is used.
Ther number of cells varies upon the driving conditions. Two cells are used only during idle, based upon TPS and
Park/Neutral switch inputs. There may be two other cells used for deceleration, based on TPS, engine rpm, and
vehicle speed. The other twelve cells represent a manifold pressure and an rpm range. Six of the cells are high rpm
and the other six are low rpm. Each of these cells has a specific MAP voltage range Typical Adaptive Memory Fuel
Cells .
As the engine enters one of these cells the PCM looks at the amount of short term correction being used. Because
the goal is to keep short term at 0 (O2 Sensor switching at 0.5 volt), long term will update in the same direction as
short term correction was moving to bring the short term back to 0. Once short term is back at 0, this long term
correction factor is stored in memory.
The values stored in long term adaptive memory are used for all operating conditions, including open loop and cold
starting. However, the updating of the long term memory occurs after the engine has exceeded approximately 170°-
190° F, with fuel control in closed loop and two minutes of engine run time. This is done to prevent any transitional
temperature or start-up compensations from corrupting long term fuel correction.
Long term adaptive memory can change the pulse-width by as much as 25%, which means it can correct for all of
short term. It is possible to have a problem that would drive long term to 25% and short term to another 25% for a
total change of 50% away from base pulse-width calculation.
Typical Adaptive Memory Fuel Cells
Open
Throttle
Open
Throttle
Open
Throttle
Open
Throttle
Open
Throttle
Open
Throttle
Idle
Decel
Vacuum
20
17
13
9
5
0
Above 1,984
rpm
1
3
5
7
9
11
13 Drive
15
Below 1,984
rpm
0
2
4
6
8
10
12
Neutral
14
MAP volt =
0
1.4
2.0
2.6
3.3
3.9
Fuel Correction Diagnostics
There are two fuel correction diagnostic routines:
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Fuel System Rich
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Fuel System Lean
A DTC is set and the MIL is illuminated if the PCM detects either of these conditions. This is determined based on
total fuel correction, short term times long term.
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FUEL INJECTION
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