Dodge Caliber. Manual — part 1439
EMISSIONS CONTROL
TABLE OF CONTENTS
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EMISSIONS CONTROL
MONITORED COMPONENT . . . . . . . . . . . . . . . . . . . 2
VEHICLE EMISSION CONTROL
INFORMATION LABEL. . . . . . . . . . . . . . . . . . . . . . . 7
SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
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EMISSIONS CONTROL
DESCRIPTION
MONITORED COMPONENT
There are several components that will affect vehicle emissions if they malfunction. If one of these components
malfunctions the Malfunction Indicator Lamp (Check Engine) will illuminate.
Some of the component monitors are checking for proper operation of the part. Electrically operated components
now have input (rationality) and output (functionality) checks as well as continuity tests (opens/shorts). Previously, a
component like the Throttle Position sensor (TPS) was checked by the PCM for an open or shorted circuit. If one of
these conditions occurred, a DTC was set. Now there is a check to ensure that the component is working. This is
done by watching for a TPS indication of a greater or lesser throttle opening than MAP and engine rpm indicate. In
the case of the TPS, if engine vacuum is high and engine rpm is 1600 or greater and the TPS indicates a large
throttle opening, a DTC will be set. The same applies to low vacuum and 1600 rpm.
Any component that has an associated limp in will set a fault after 1 trip with the malfunction present.
Refer to the Diagnostic Trouble Codes Description Charts in this section and the appropriate Powertrain Diagnostic
Procedure Manual for diagnostic procedures.
The following is a list of the monitored components:
•
Catalyst Monitor
•
Comprehensive Components
•
EGR (if equipped)
•
Fuel Control (rich/lean)
•
Oxygen Sensor Monitor
•
Oxygen Sensor Heater Monitor
•
Purge
•
Misfire
•
Evaporative System Integrity Monitor (ESIM)
COMPREHENSIVE COMPONENTS
Along with the major monitors, OBD II requires that the diagnostic system monitor any component that could affect
emissions levels. In many cases, these components were being tested under OBD I. The OBD I requirements
focused mainly on testing emissions-related components for electrical opens and shorts.
However, OBD II also requires that inputs from powertrain components to the PCM be tested for rationality, and
that outputs to powertrain components from the PCM be tested for functionality. Methods for monitoring the vari-
ous Comprehensive Component monitoring include:
1. Circuit Continuity
•
Open
•
Shorted high
•
Shorted to ground
2. Rationality or Proper Functioning
•
Inputs tested for rationality
•
Outputs tested for functionality
NOTE: Comprehensive component monitors are continuous. Therefore, enabling conditions do not apply.
All will set a DTC and illuminate the MIL in 1- trip.
Input Rationality—While input signals to the PCM are constantly being monitored for electrical opens and shorts,
they are also tested for rationality. This means that the input signal is compared against other inputs and information
to see if it makes sense under the current conditions.
PCM sensor inputs that are checked for rationality include:
•
Manifold Absolute Pressure (MAP) Sensor
•
Oxygen Sensor (O2S) (slow response)
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EMISSIONS CONTROL
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•
Engine Coolant Temperature (ECT) Sensor
•
Camshaft Position (CMP) Sensor
•
Vehicle Speed Sensor
•
Crankshaft Position (CKP) Sensor
•
Inlet Air Temperature Sensor
•
Throttle Position (TPS) Sensor
•
Power Steering Switch
•
Oxygen Sensor Heater
•
Engine Controller
•
Brake Switch
•
Evaporative System Integrity Monitor (ESIM)
•
P/N Switch
•
Trans Controls
Output Functionality—PCM outputs are tested for functionality in addition to testing for opens and shorts. When
the PCM provides a voltage to an output component, it can verify that the command was carried out by monitoring
specific input signals for expected changes. For example, when the PCM commands the Idle Air Control (IAC) Motor
to a specific position under certain operating conditions, it expects to see a specific (target) idle speed (RPM). If it
does not, it stores a DTC.
PCM outputs monitored for functionality include:
•
Fuel Injectors
•
Ignition Coils
•
Torque Converter Clutch Solenoid
•
Purge Solenoid
•
EGR Solenoid (if equipped)
•
Radiator Fan Control
•
Trans Controls
OXYGEN SENSOR (O2S) MONITOR
DESCRIPTION—Effective control of exhaust emissions is achieved by an oxygen feedback system. The most
important element of the feedback system is the O2S. The O2S is located in the exhaust path. Once it reaches
operating temperature 300° to 350°C (572° to 662°F), the sensor generates a voltage that is inversely proportional
to the amount of oxygen in the exhaust. When there is a large amount of oxygen in the exhaust caused by a lean
condition, misfire or exhaust leak, the sensor produces a low voltage, below 450 mV. When the oxygen content is
lower, caused by a rich condition, the sensor produces a higher voltage, above 450mV.
The information obtained by the sensor is used to calculate the fuel injector pulse width. The PCM is programmed
to maintain the optimum air/fuel ratio. At this mixture ratio, the catalyst works best to remove hydrocarbons (HC),
carbon monoxide (CO) and nitrous oxide (NOx) from the exhaust.
The O2S is also the main sensing element for the EGR, Catalyst and Fuel Monitors, and purge.
The O2S may fail in any or all of the following manners:
•
Slow response rate (Big Slope)
•
Reduced output voltage (Half Cycle)
•
Heater Performance
Slow Response Rate (Big Slope)—Response rate is the time required for the sensor to switch from lean to rich
signal output once it is exposed to a richer than optimum A/F mixture or vice versa. As the PCM adjusts the air/fuel
ratio, the sensor must be able to rapidly detect the change. As the sensor ages, it could take longer to detect the
changes in the oxygen content of the exhaust gas. The rate of change that an oxygen sensor experiences is called
’Big Slope’. The PCM checks the oxygen sensor voltage in increments of a few milliseconds.
Reduced Output Voltage (Half Cycle)—The output voltage of the O2S ranges from 2.5 to 5 volt. A good sensor
can easily generate any output voltage in this range as it is exposed to different concentrations of oxygen. To detect
a shift in the A/F mixture (lean or rich), the output voltage has to change beyond a threshold value. A malfunctioning
sensor could have difficulty changing beyond the threshold value. Many times the condition is only temporary and
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the sensor will recover. Under normal conditions the voltage signal surpasses the threshold, and a counter is incre-
mented by one. This is called the Half Cycle Counter.
Heater Performance—The heater is tested by a separate monitor. Refer to the Oxygen Sensor Heater Monitor.
OPERATION—As the Oxygen Sensor signal switches, the PCM monitors the half cycle and big slope signals from
the oxygen sensor. If during the test neither counter reaches a predetermined value, a malfunction is entered and a
Freeze Frame is stored. Only one counter reaching its predetermined value is needed for the monitor to pass.
The Oxygen Sensor Signal Monitor is a two trip monitor that is tested only once per trip. When the Oxygen Sensor
fails the test in two consecutive trips, the MIL is illuminated and a DTC is set. The MIL is extinguished when the
Oxygen Sensor monitor passes in three consecutive trips. The DTC is erased from memory after 40 consecutive
warm-up cycles without test failure.
Enabling Conditions—The following conditions must typically be met for the PCM to run the oxygen sensor mon-
itor:
•
Battery voltage
•
Engine temperature
•
Engine run time
•
Engine run time at a predetermined speed
•
Engine run time at a predetermined speed and throttle opening
•
Transmission in gear (automatic only)
•
Fuel system in Closed Loop
•
Long Term Adaptive (within parameters)
•
Power Steering Switch in low PSI (no load)
•
Engine at idle
•
Fuel level above 15%
•
Barometric pressure
•
Engine RPM within acceptable range of desired idle
•
Closed throttle speed
Pending Conditions—The Task Manager typically does not run the Oxygen Sensor Signal Monitor if overlapping
monitors are running or the MIL is illuminated for any of the following:
•
Misfire Monitor
•
Front Oxygen Sensor and Heater Monitor
•
MAP Sensor
•
Vehicle Speed Sensor
•
Engine Coolant Temperature Sensor
•
Throttle Position
•
Engine Controller Self Test Faults
•
Cam or Crank Sensor
•
Injector and Coil
•
EVAP Electrical
•
EGR Solenoid Electrical (if equipped)
•
Intake Air Temperature
•
5 Volt Feed
Conflict—The Task Manager does not run the Oxygen Sensor Monitor if any of the following conditions are present:
•
A/C ON (A/C clutch cycling temporarily suspends monitor)
•
Purge flow in progress
Suspend—The Task Manager suspends maturing a fault for the Oxygen Sensor Monitor if an of the following are
present:
•
Oxygen Sensor Heater Monitor, Priority 1
•
Misfire Monitor, Priority 2
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