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Chrysler Crossfire. Manual - part 1016

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Engine Controller

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Brake Switch

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Evaporative Vacuum Leak Detection (EVLD)

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P/N Switch

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Transmission 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 Electronic Throttle Control
(ETC) 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:

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Fuel Injectors

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Air Pump Switchover Solenoid

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Short Runner Valve Solenoid

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Ignition Coils

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Throttle Body (Electronic Throttle Control/Throttle Position Sensor)

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Purge Solenoid

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EGR Solenoid

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Radiator Fan Control

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Transmission 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 450mV. 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, Purge System, and Catalyst and Fuel Monitors.

The O2S may fail in any or all of the following manners:

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Slow response rate (Big Slope)

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Reduced output voltage (Half Cycle)

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Heater Performance

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Dynamic shift

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Shorted or open circuits

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 air/fuel 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 0 to 1 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 air/fuel mixture (lean or rich), the output voltage has to change beyond a threshold value. A malfunc-
tioning sensor could have difficulty changing beyond the threshold value. Many times, the condition is only tempo-
rary and the sensor will recover. Under normal conditions, the voltage signal surpasses the threshold and a counter
is incremented by one. This is called the Half Cycle Counter.

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.

EMISSIONS CONTROL

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The Oxygen Sensor Signal Monitor is a 2 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.

OXYGEN SENSOR HEATER MONITOR

DESCRIPTION - If the Oxygen Sensor (O2S) DTC as well as a O2S heater DTC is present, the O2S Heater DTC
MUST be repaired first. After the O2S Heater is repaired, verify that the sensor circuit is operating correctly.

Note: The O2S Heaters are kept off at coolant temperatures below 20°C (68°F) and at high engine rpm in
order to avoid damaging the heaters. The voltage reading taken from the O2S are very temperature sensitive.
The readings taken from the O2S are not accurate below 300°C (572°F). Heating the O2S is done to allow the
engine controller to shift to closed loop control as soon as possible. The heating element used to heat the O2S
must be tested to ensure that it is heating the sensor properly. The heater resistance is checked by the PCM almost
immediately after the engine is started. The same O2S heater return pin used to read the heater resistance is capa-
ble of detecting an open, shorted high or shorted low circuit.

OPERATION - The Oxygen Sensor Heater Monitor begins after the ignition has been turned OFF and the O2 sen-
sors have cooled. As the sensor cools down, the resistance increases and the PCM reads the increase in voltage.
Once voltage has increased to a predetermined amount, higher than when the test started, the oxygen sensor is
cool enough to test heater operation.

When the oxygen sensor is cool enough, the PCM provides a ground path for the O2S heater circuit. Voltage to the
O2 sensor begins to increase the temperature. As the sensor temperature increases, the internal resistance
decreases.

The heater elements are tested each time the engine is turned OFF if all the enabling conditions are met. If the
monitor fails, the PCM stores a maturing fault and a Freeze Frame is entered. If two consecutive tests fail, a DTC
is stored. Because the ignition is OFF, the MIL is illuminated at the beginning of the next key cycle, after the 2nd
failure.

CATALYST MONITOR

DESCRIPTION - To comply with clean air regulations, vehicles are equipped with catalytic converters. These con-
verters reduce the emission of hydrocarbons, oxides of nitrogen and carbon monoxide.

Normal vehicle miles or engine misfire can cause a catalyst to decay. A meltdown of the ceramic core can cause a
restriction of the exhaust. This can increase vehicle emissions and deteriorate engine performance, driveability and
fuel economy.

The catalyst monitor uses dual oxygen sensors (O2Ss) to monitor the efficiency of the converter. The dual O2S
strategy is based on the fact that as a catalyst deteriorates, its oxygen storage capacity and its efficiency are both
reduced. By monitoring the oxygen storage capacity of a catalyst, its efficiency can be indirectly calculated. The
upstream O2S is used to detect the amount of oxygen in the exhaust gas before the gas enters the catalytic con-
verter. The PCM calculates the air/fuel mixture from the output of the O2S. A low voltage indicates high oxygen
content (lean mixture). A high voltage indicates a low content of oxygen (rich mixture).

When the upstream O2S detects a high oxygen condition, there is an abundance of oxygen in the exhaust gas. A
functioning converter would store this oxygen so it can use it for the oxidation of HC and CO. As the converter
absorbs the oxygen, there will be a lack of oxygen downstream of the converter. The output of the downstream O2S
will indicate limited activity in this condition.

As the converter loses the ability to store oxygen, the condition can be detected from the behavior of the down-
stream O2S. When the efficiency drops, no chemical reaction takes place. This means the concentration of oxygen
will be the same downstream as upstream. The output voltage of the downstream O2S copies the voltage of the
upstream sensor. The only difference is a time lag (seen by the PCM) between the switching of the O2Ss.

To monitor the system, the number of lean-to-rich switches of upstream and downstream O2Ss is counted. The ratio
of downstream switches to upstream switches is used to determine whether the catalyst is operating properly. An
effective catalyst will have fewer downstream switches than it has upstream switches i.e., a ratio closer to zero. For
a totally ineffective catalyst, this ratio will be one-to-one, indicating that no oxidation occurs in the device.

The system must be monitored so that when catalyst efficiency deteriorates and exhaust emissions increase to over
the legal limit, the MIL will be illuminated.

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EMISSIONS CONTROL

OPERATION - To monitor catalyst efficiency, the PCM expands the rich and lean switch points of the heated oxygen
sensor. With extended switch points, the air/fuel mixture runs richer and leaner to overburden the catalytic converter.
Once the test is started, the air/fuel mixture runs rich and lean and the O2S switches are counted. A switch is
counted when an oxygen sensor signal goes from below the lean threshold to above the rich threshold. The number
of Rear O2S switches is divided by the number of Front O2S switches to determine the switching ratio.

The test runs for 20 seconds. As catalyst efficiency deteriorates over the life of the vehicle, the switch rate at the
downstream sensor approaches that of the upstream sensor. If at any point during the test period the switch ratio
reaches a predetermined value, a counter is incremented by one. The monitor is enabled to run another test during
that trip. When the test fails three times, the counter increments to three, a malfunction is entered, and a Freeze
Frame is stored. When the counter increments to three during the next trip, the code is matured and the MIL is
illuminated. If the test passes the first, no further testing is conducted during that trip.

The MIL is extinguished after three consecutive good trips.

DESCRIPTION - MONITORED SYSTEMS

There are new electronic circuit monitors that check fuel, emission, engine and ignition performance. These moni-
tors use information from various sensor circuits to indicate the overall operation of the fuel, engine, ignition and
emission systems and thus the emissions performance of the vehicle.

The fuel, engine, ignition and emission system monitors do not indicate a specific component problem. They do
indicate that there is an implied problem within one of the systems and that a specific problem must be diagnosed.

If any of these monitors detect a problem affecting vehicle emissions, the Malfunction Indicator Lamp (MIL) will be
illuminated. These monitors generate Diagnostic Trouble Codes that can be displayed with the a DRB III

scan tool.

The following is a list of the system monitors:

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EGR Monitor

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Misfire Monitor

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Fuel System Monitor

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Oxygen Sensor Monitor

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Oxygen Sensor Heater Monitor

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Catalyst Monitor

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Evaporative Vacuum Leak Detection System Monitor

Following is a description of each system monitor and its DTC.

Refer to the appropriate Powertrain Diagnostic Procedures manual for diagnostic procedures.

OXYGEN SENSOR (O2S) MONITOR

The O2S is also the main sensing element for the EGR, Purge System, and Catalyst and Fuel Monitors.

The O2S may fail in any or all of the following manners:

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Slow response rate (Big Slope)

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Reduced output voltage (Half Cycle)

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Heater Performance

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Dynamic shift

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Shorted or open circuits

EMISSIONS CONTROL

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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 0 to 1 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 air/fuel mixture (lean or rich), the output voltage has to change beyond a threshold value. A malfunc-
tioning sensor could have difficulty changing beyond the threshold value. Many times, the condition is only tempo-
rary and the sensor will recover. Under normal conditions the voltage signal surpasses the threshold and a counter
is incremented by one. This is called the Half Cycle Counter.

OXYGEN SENSOR HEATER MONITOR

EGR MONITOR

The Powertrain Control Module (PCM) performs an on-board diagnostic check of the EGR system.

The EGR monitor is used to test whether the EGR system is operating within specifications. The diagnostic check
activates only during selected engine/driving conditions. When the conditions are met, the EGR is turned off (sole-
noid de-energized) and the O2S compensation control is monitored. Turning off the EGR shifts the air/fuel ratio in
the lean direction. The O2S data should indicate an increase in the O2 concentration in the combustion chamber
when the exhaust gases are no longer recirculated. While this test does not directly measure the operation of the
EGR system, it can be inferred from the shift in the O2S data whether the EGR system is operating correctly.
Because the O2S is being used, the O2S test must pass its test before the EGR test. This monitor also looks at
EGR linear potentiometer for feedback.

MISFIRE MONITOR

Excessive engine misfire results in increased catalyst temperature and causes an increase in HC emissions. Severe
misfires could cause catalyst damage. To prevent catalytic convertor damage, the PCM monitors engine misfire.

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EMISSIONS CONTROL

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