Emissions Control System Chrysler Crossfire I final

SCAN TOOL STATE DISPLAY TEST MODE

The switch (component) inputs to the Powertrain Control Module (PCM) have two recognized states; HIGH and LOW. The PCM cannot recognize the difference between a selected switch position versus an open circuit, a short circuit or a defective switch. If the State Display screen shows the change from HIGH to LOW or LOW to HIGH, assume the entire switch circuit to the PCM functions properly. From the state display screen, access either State Display Inputs and Outputs or State Display Sensors.

NON-MONITORED SYSTEMS

The PCM does not monitor all circuits, systems and conditions that could have malfunctions causing driveability problems. However, malfunctions in these systems may cause the PCM to store diagnostic trouble codes for other systems or components. For example, a fuel pressure problem will not register a fault directly but could cause a rich/lean condition or misfire. This could cause the PCM to store an oxygen sensor or misfire diagnostic trouble code.

The major non-monitored circuits are listed below along with examples of failure modes that do not directly cause the PCM to set a DTC, but instead for a system that is monitored.

FUEL PRESSURE

The fuel pressure regulator controls fuel system pressure. The PCM cannot detect a clogged fuel pump inlet filter, clogged in-line fuel filter, or a pinched fuel supply or return line. However, these could result in a rich or lean condition causing the PCM to store an oxygen sensor, fuel system, or misfire diagnostic trouble code.

SECONDARY IGNITION CIRCUIT

The PCM cannot detect an inoperative ignition coil, fouled or worn spark plugs, ignition cross firing, or open spark plug cables. The misfire will, however, increase the oxygen content in the exhaust, deceiving the PCM into thinking the fuel system is too lean. Also see misfire detection.

CYLINDER COMPRESSION

The PCM cannot detect uneven, low, or high engine cylinder compression. Low compression lowers O2 content in the exhaust, leading to a fuel system, oxygen sensor or misfire detection fault.

EXHAUST SYSTEM

The PCM cannot detect a plugged, restricted or leaking exhaust system. It may set an EGR, Fuel system or O2S fault.

FUEL INJECTOR MECHANICAL MALFUNCTIONS

The PCM cannot determine if a fuel injector is clogged, the needle is sticking or if the wrong injector is installed. However, these could result in a rich or lean condition causing the PCM to store a diagnostic trouble code for either misfire, an oxygen sensor or the fuel system.

EXCESSIVE OIL CONSUMPTION

Although the PCM monitors engine exhaust oxygen content when the system is in closed loop, it cannot determine excessive oil consumption.

THROTTLE BODY AIR FLOW

The PCM cannot detect a clogged or restricted air cleaner inlet or filter element.

VACUUM ASSIST

The PCM cannot detect leaks or restrictions in the vacuum circuits of vacuum assisted engine control system devices or vacuum assisted accessories. However, these could cause the PCM to store a MAP sensor diagnostic trouble code and cause a high idle condition.

PCM SYSTEM GROUND

The PCM cannot determine a poor system ground. However, one or more diagnostic trouble codes may be generated as a result of this condition.

PCM CONNECTOR ENGAGEMENT

The PCM may not be able to determine spread or damaged connector pins. However, it might store diagnostic trouble codes as a result of pins not making good contact.

HIGH AND LOW LIMITS

The PCM compares input signal voltages from each input device with established high and low limits for the device. If the input voltage is not within limits and other criteria are met, the PCM stores a diagnostic trouble code in memory. Other diagnostic trouble code criteria might include engine RPM limits or input voltages from other sensors or switches that must be present before verifying a diagnostic trouble code condition.

VEHICLE EMISSION CONTROL INFORMATION LABEL

All models have a Vehicle Emission Control Information (VECI) Label. DaimlerChrysler permanently attaches the label in the engine compartment. It cannot be removed without defacing information and destroying the label.

The label contains the vehicle's emission specifications and vacuum hose routings. All hoses must be connected and routed according to the label.

Scheme 3

There are several components that will affect vehicle emissions if they malfunction. If one of these components malfunctions, the Malfunction Indicator Lamp (MIL) 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 Powertrain Control Module (PCM) for an open or shorted circuit. If one of these conditions occurred, a Diagnostic Trouble Code (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 Manifold Absolute Pressure (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 appropriate Engine ELECTRICAL DIAGNOSTICS article for diagnostic procedures.

The following is a list of the monitored components

1. Catalyst Monitor
2. Comprehensive Components
3. Exhaust Gas Recirculation (EGR)
4. Fuel Control (rich/lean)
5. Oxygen Sensor Monitor
6. Oxygen Sensor Heater Monitor
7. Purge
8. Misfire
9. Evaporative Vacuum Leak Detection (EVLD)

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 various Comprehensive Component monitoring include

1. Circuit Continuity
2. Open
3. Shorted to Voltage
4. Shorted to Ground
5. Rationality and Functionality
6. 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 and CAN Bus inputs that are checked for rationality include

1. Manifold Absolute Pressure (MAP) Sensor
2. Oxygen Sensor (O2S) (slow response)
3. Engine Coolant Temperature (ECT) Sensor
4. Camshaft Position (CMP) Sensor
5. Vehicle Speed from the Controller Antilock Brake (CAB)
6. Crankshaft Position (CKP) Sensor
7. Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor
8. Accelerator Pedal Position Sensor (APPS)
9. Throttle Position Sensor (TPS)
10. Knock Sensors
11. Oxygen Sensor Heater
12. Engine Controller
13. Brake Switch
14. Evaporative Vacuum Leak Detection (EVLD)
15. P/N Switch
16. 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

1. Fuel Injectors
2. Air Pump Switchover Solenoid
3. Short Runner Valve Solenoid
4. Ignition Coils
5. Throttle Body (Electronic Throttle Control/Throttle Position Sensor)
6. Purge Solenoid
7. EGR Solenoid
8. Radiator Fan Control
9. 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

1. Slow response rate (Big Slope)
2. Reduced output voltage (Half Cycle)
3. Heater Performance
4. Dynamic shift
5. 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 malfunctioning sensor could have difficulty changing beyond the threshold value. Many times, the condition is only temporary 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.

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 capable 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 sensors 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 converters 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 converter. 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 downstream 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.

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.

TRIP DEFINITION

A "Trip" means vehicle operation (following an engine-off period) of duration and driving mode such that all components and systems are monitored at least once by the diagnostic system. The monitors must successfully pass before the PCM can verify that a previously malfunctioning component is meeting the normal operating conditions of that component. For misfire or fuel system malfunction, the MIL may be extinguished if the fault does not recur when monitored during three subsequent sequential driving cycles in which conditions are similar to those under which the malfunction was first determined.

Anytime the MIL is illuminated, a DTC is stored. The DTC can self erase only after the MIL has been extinguished. Once the MIL is extinguished, the PCM must pass the diagnostic test for the most recent DTC for 40 warm-up cycles (80 warm-up cycles for the Fuel System Monitor and the Misfire Monitor). A warm-up cycle can best be described by the following

1. The engine must be running
2. A rise of 4.4°C (40°F) in engine temperature must occur from the time engine was started
3. Engine coolant temperature must crossover 71°C (160°F)
4. A "driving cycle" that consists of engine start up and engine shut off.

Once the above conditions occur, the PCM is considered to have passed a warm-up cycle. Due to the conditions required to extinguish the MIL and erase the DTC, it is most important that after a repair has been made, all DTCs be erased and the repair verified by running 1 good trip.

MONITORED SYSTEMS

There are new electronic circuit monitors that check fuel, emission, engine and ignition performance. These monitors 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 scan tool.

The following is a list of the system monitors

1. EGR Monitor
2. Misfire Monitor
3. Fuel System Monitor
4. Oxygen Sensor Monitor
5. Oxygen Sensor Heater Monitor
6. Catalyst Monitor
7. Evaporative Vacuum Leak Detection System Monitor

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

Refer to the appropriate Engine ELECTRICAL DIAGNOSTICS article for diagnostic procedures.

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

1. Slow response rate (Big Slope)
2. Reduced output voltage (Half Cycle)
3. Heater Performance
4. Dynamic shift
5. 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 malfunctioning sensor could have difficulty changing beyond the threshold value. Many times, the condition is only temporary 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.

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.

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 capable 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 sensors 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.

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 (solenoid 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.

The Powertrain Control Module (PCM) monitors for misfire during most engine operating conditions (positive torque) by looking at changes in the crankshaft speed. If a misfire occurs, the speed of the crankshaft will vary more than normal.

FUEL SYSTEM MONITOR

The PCM is programmed to maintain the optimum air/fuel ratio. This is done by making short term corrections in the fuel injector pulse width based on the O2S output. The programmed memory acts as a self-calibration tool that the engine controller uses to compensate for variations in engine specifications, sensor tolerances and engine fatigue over the life span of the engine. By monitoring the actual air/fuel ratio with the O2S (short term) and multiplying that with the program long term (adaptive) memory calculation, then comparing that to the limit, it can be determined whether it will pass an emissions test. If a malfunction occurs such that the PCM cannot maintain the optimum air/fuel ratio, then the MIL will be illuminated.

DESCRIPTION - To comply with clean air regulations, vehicles are equipped with catalytic converters. These converters 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 converter. 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 downstream 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.

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.

Scheme 4

The Evaporative Vacuum Leak Detection (EVLD) system has replaced the leak detection pump as the method of evaporative system leak detection. This is to detect a leak equivalent to a 0.5 mm (0.020 in.) hole. This system has the capability to detect holes of this size very dependably. In addition to the detection of very small leaks, this system has the capability of detecting medium as well as large evaporative system leaks.

The EVLD system incorporates the EVAP Purge Hoses, EVAP Canister, fuel tank, fuel filler neck and fuel filler cap with the Charcoal Canister Shutoff Valve, EVAP Purge Solenoid, PCM and engine vacuum to detect a leak in the purge system.

The PCM seals the Charcoal Canister Shutoff Valve and opens the EVAP Purge Solenoid to perform the 3-stage leak test after the following conditions have been met

1. Battery voltage > 11 volts
2. Engine running for approximately 16 minutes
3. Engine idling
4. Vehicle at rest
5. Emission controls in closed loop
6. Intake air temperature less than 45°C (113°F)
7. Engine coolant temperature at startup < 100°C (212°F)
8. Engine load < 35%
9. Transmission in Drive or Reverse
10. Secondary air injection not active
11. Atmospheric pressure > 780 hPa (11.31 psi) i.e, altitude > 8200 feet
12. Low purge canister activity
13. Fuel tank level between 1/4 and 3/4
14. No excessive fuel slosh in the fuel tank
15. No fault in the Charcoal Canister Shutoff Valve, EVAP Purge Solenoid, or Fuel Tank Pressure Sensor
16. No leak in the ORVR Pressure Relief Valve

The leak test consists of three successive tests that are dependent on the previous test passing. If one test fails, the next test will not be run. The major leak test begins by closing the Charcoal Canister Shutoff Valve and opening the EVAP Purge Solenoid to allow engine vacuum to build to 6 mbar (2.4 in. H2O), as measured by the Fuel Tank Pressure Sensor, in the fuel tank within approximately 12 seconds. If there is no vacuum buildup in the fuel tank, there is a major leak present, the leak test is aborted, the Low Fuel Warning Indicator is illuminated in the instrument cluster and a DTC is stored in the PCM.

If the major leak test passes, the EVAP Purge Solenoid is closed when vacuum inside the fuel tank reaches approximately 6 mbar (2.4 in. H2O) and the vacuum is analyzed for approximately 30 seconds. The vacuum must not drop by more than 0.3 to 0.5 mbar (0.12 to 0.2 in. H2O), depending on the fuel level in the fuel tank, during the 30 second time period. If there is a minor leak, the leak test is aborted and a DTC is stored in the PCM. The leak test will be aborted if an excessive lean correction occurs during vacuum buildup.

If the minor leak test passes, the micro leak test initiates by again bringing the vacuum in the fuel tank up to approximately 6 mbar (2.4 in.H2O). Once the vacuum in the fuel tank is reestablished, the EVAP Purge Solenoid is closed. The vacuum must not drop by more than 0.1 to 0.15 mbar (0.04 to 0.06 in. H2O), depending on the fuel level in the fuel tank, per second. If the vacuum drops more rapidly, a DTC is stored in the PCM. The leak test will be aborted if an excessive lean correction occurs during vacuum buildup.

When the leak test is complete, the EVAP Purge Solenoid is opened and the purge control system returns to normal operation.

EMISSION CONTROL SYSTEM - LHD

The Powertrain Control Module (PCM) monitors many different circuits in the fuel injection, ignition, emission and engine systems. If the PCM senses a problem with a monitored circuit often enough to indicate an actual problem, it stores a Diagnostic Trouble Code (DTC) in the PCM's memory. If the code applies to a non-emissions related component or system and the problem is repaired or ceases to exist, the PCM cancels the code after 40 warm-up cycles. Diagnostic trouble codes that affect vehicle emissions illuminate the Malfunction Indicator Lamp (MIL).

Certain criteria must be met before the PCM stores a DTC in memory. The criteria may be a specific range of engine RPM, engine temperature, and/or input voltage to the PCM.

The PCM might not store a DTC for a monitored circuit even though a malfunction has occurred. This may happen because one of the DTC criteria for the circuit has not been met. For example , assume the diagnostic trouble code criteria requires the PCM to monitor the circuit only when the engine operates between 750 and 2000 RPM. Suppose the sensor's output circuit shorts to ground when the engine operates above 2400 RPM (resulting in 0 volt input to the PCM). Because the condition happens at an engine speed above the maximum threshold (2000 RPM), the PCM will not store a DTC.

There are several operating conditions for which the PCM monitors and sets DTCs. Refer to DESCRIPTION - MONITORED SYSTEMS , DESCRIPTION - MONITORED COMPONENTS and DESCRIPTION - NON-MONITORED SYSTEMS .

Note. Various diagnostic procedures may actually cause a diagnostic monitor to set a DTC. For instance, pulling a spark plug wire to perform a spark test may set the misfire code. When a repair is completed and verified, use the Scan Tool to erase all DTCs and extinguish the MIL.

Scheme 5

Technicians can retrieve stored DTCs. For obtaining the DTC information, use the Data Link Connector (2) with the scan tool scan tool.

EMISSION CONTROL SYSTEM - RHD

The Powertrain Control Module (PCM) monitors many different circuits in the fuel injection, ignition, emission and engine systems. If the PCM senses a problem with a monitored circuit often enough to indicate an actual problem, it stores a Diagnostic Trouble Code (DTC) in the PCM's memory. If the code applies to a non-emissions related component or system and the problem is repaired or ceases to exist, the PCM cancels the code after 40 warm-up cycles. Diagnostic trouble codes that affect vehicle emissions illuminate the Malfunction Indicator Lamp (MIL).

Certain criteria must be met before the PCM stores a DTC in memory. The criteria may be a specific range of engine RPM, engine temperature, and/or input voltage to the PCM.

The PCM might not store a DTC for a monitored circuit even though a malfunction has occurred. This may happen because one of the DTC criteria for the circuit has not been met. For example , assume the diagnostic trouble code criteria requires the PCM to monitor the circuit only when the engine operates between 750 and 2000 RPM. Suppose the sensor's output circuit shorts to ground when the engine operates above 2400 RPM (resulting in 0 volt input to the PCM). Because the condition happens at an engine speed above the maximum threshold (2000 RPM), the PCM will not store a DTC.

There are several operating conditions for which the PCM monitors and sets DTCs. Refer to DESCRIPTION - MONITORED SYSTEMS , DESCRIPTION - MONITORED COMPONENTS and DESCRIPTION - NON-MONITORED SYSTEMS .

Note. Various diagnostic procedures may actually cause a diagnostic monitor to set a DTC. For instance, pulling a spark plug wire to perform a spark test may set the misfire code. When a repair is completed and verified, use the scan tool scan tool to erase all DTCs and extinguish the MIL.

Scheme 6

Technicians can retrieve stored DTCs. For obtaining the DTC information, use the Data Link Connector (2) with the scan tool scan tool.

The Evaporation Control System prevents the emission of fuel tank vapors into the atmosphere. When fuel evaporates in the fuel tank, the vapors pass through vent hoses or tubes to an activated carbon filled evaporative canister. The canister temporarily holds the vapors. The Powertrain Control Module (PCM) allows intake manifold vacuum to draw vapors into the combustion chambers during certain operating conditions.

This vehicle uses a pulse-width modulated EVAP Purge Solenoid System. The PCM controls vapor flow by operating the EVAP Purge Solenoid. Refer to EVAP PURGE SOLENOID .

Note. The evaporative system uses specially manufactured hoses. If they need replacement, only use fuel resistant hose. Also the hoses must be able to pass an Ozone compliance test.

Note. For more information on Onboard Refueling Vapor Recovery (ORVR), refer to FUEL DELIVERY .

Scheme 7

The Crankcase Ventilation (CCV) system performs the same function as a conventional PCV system, but does not use a vacuum controlled valve.

1. Check each CCV system tube (line) (1 and 3) and the draft-tube style insert (2) for leaks, cracks, kinks or bends. Replace as necessary.
2. Disconnect each CCV tube (1 and 3).
3. Blow compressed air through each tube (1 and 3) and the draft-tube style insert (2). Check for blockage or restrictions. If cleaning is necessary, spray a soapy-type all-purpose cleaner into each component and blow out. After restriction is cleared, rinse out component with clear water. Blow water from component and install to vehicle. To prevent damage to plastic components, never spray carburetor-type cleaner into any of the plastic tubes.

DESCRIPTION - CHARCOAL CANISTER SHUTOFF VALVE

The Charcoal Canister Shutoff Valve is part of the Evaporative Vacuum Leak Detection (EVLD) system. The Charcoal Canister Shutoff Valve is mounted on the EVAP Canister. This assembly is located above a splash shield in front of the right rear axle shaft.

OPERATION - CHARCOAL CANISTER SHUTOFF VALVE

The Charcoal Canister Shutoff Valve is actuated by the PCM to isolate the EVAP Purge System in order to determine if a leak exists in any of the purge system components.

REMOVAL - CHARCOAL CANISTER SHUTOFF VALVE

For removal procedure, see REMOVAL .

INSTALLATION - CHARCOAL CANISTER SHUTOFF VALVE

For installation procedure, see INSTALLATION .

Scheme 8

Crankcase ventilation is accomplished by means of a draft-tube style insert (2) protruding through the throttle body into the intake airstream (4). The crankcase gases are drawn into the intake manifold when air passing the tube insert creates a vacuum in the Crankcase Vent Hoses (1 and 3).

DESCRIPTION

The Positive Crankcase Ventilation (PCV) System consists of a draft-tube style throttle body insert (2) and hoses (1 and 3) connected between the cylinder head covers and the throttle body insert (2).

This vehicle uses a pulse-width modulated EVAP Purge Solenoid. The solenoid regulates the rate of vapor flow from the EVAP canister to the throttle body. The PCM controls the frequency at which the solenoid operates in order to customize the vapor volume for each cylinder.

OPERATION

The PCM will only energize the EVAP solenoid when the engine is at operating temperature, but will de-energize it during periods of deceleration. When de-energized, no vapors are purged.

The pulse-width modulated EVAP Purge Solenoid controls the fuel vapor purge rate from the Vapor Canister and fuel tank to the engine intake manifold.

Scheme 9

1. Disconnect harness connector from solenoid (2).
2. Disconnect vapor hoses (1 and 4) from solenoid (3).
3. Remove solenoid (3) from bracket (5).

Scheme 10

1. Disconnect harness connector from solenoid (2).
2. Disconnect vapor hoses (1 and 4) from solenoid (3).
3. Remove solenoid (3) from bracket (5).

INSTALLATION - LHD

1. Install solenoid (3) on bracket (5).
2. Connect vapor hoses (1 and 4) to solenoid (3).
3. Connect connector (2) to solenoid (3).

INSTALLATION - RHD

1. Install solenoid (3) on bracket (5).
2. Connect vapor hoses (1 and 4) to solenoid (3).
3. Connect connector (2) to solenoid (3).

DESCRIPTION - FUEL FILLER CAP

The plastic/metal Fuel Filler Cap is installed with a 1/4 turn onto the end of the fuel filler tube. Its purpose is to retain vapors and fuel in the fuel tank.

OPERATION - FUEL FILLER CAP

The Fuel Filler Cap incorporates a two-way relief valve that is closed to atmosphere during normal operating conditions. The relief valve is calibrated to open when a pressure of 172 mbar (2.5 psi) or vacuum of 20 mbar (8 in. H2O) occurs in the fuel tank. When the pressure or vacuum is relieved, the valve returns to the normally closed position.

DESCRIPTION - ONBOARD REFUELING VAPOR RECOVERY

The Onboard Refueling Vapor Recovery (ORVR) System is used to remove excess vapors in the fuel tank during refueling.

Scheme 11

The Onboard Refueling Vapor Recovery (ORVR) System is an emission control device. The principle used in the ORVR system is that the fuel flowing into the fuel filler tube (3) creates an aspiration effect which draws air into the fuel filler tube (3). During refueling, the fuel tank (2) is vented to the EVAP Canister (7) to capture escaping vapors. With air flowing into the fuel filler tube (3), there are no fuel vapors escaping to the atmosphere. Once the refueling vapors are captured by the EVAP Canister (7), the vehicle's computer controlled purge system draws vapor out of the canister for the engine to burn. The vapor flow is metered by the EVAP Purge Solenoid (6) so that there is minimal or no impact on driveability or tailpipe emissions.

As fuel starts to flow through the Fuel Filler Tube (3), it opens the normally closed Fuel Filler Tube Check Valve (4) and enters the Fuel Tank (2). Vapor or air is expelled from the tank through the tank vent/rollover valves (1) to the EVAP Canister (7). Vapor is absorbed in the canister (7) until vapor flow in the lines stops, either following refueling shut-off or by having the fuel level in the tank rise high enough to close the check valves in the tank vent/rollover valves (1). The fuel filler tube (3) also incorporates a fuel tank overfill check valve (5). As fuel level rises, the fuel tank overfill check valve (5) seals the in-tank end of the fuel filler tube (3). This largely prevents overfilling of the Fuel Tank (2). At this point in the fueling of the vehicle, the tank pressure increases, the fuel filler tube check valve (4) closes (preventing tank fuel from spitting back at the operator), and fuel then rises up the filler tube (3) to shut-off the dispensing nozzle.

DESCRIPTION - VAPOR CANISTER

The EVAP Canister is located above a splash shield in front of the right rear axle shaft.

OPERATION - VAPOR CANISTER

This vehicle uses a maintenance-free, Evaporative (EVAP) Canister filled with activated carbon granules. Fuel tank vapors are vented into the canister where they are absorbed by the activated carbon granules. The canister temporarily holds the fuel vapors until intake manifold vacuum draws them into the combustion chamber. The Powertrain Control Module (PCM) purges the canister through the pulse-width modulated EVAP Purge Solenoid. The PCM purges the canister at predetermined intervals and engine conditions.

Scheme 12

Scheme 13

1. Disconnect the negative battery cable.
2. Raise and support the vehicle.
3. Remove the shield retaining nuts from splash shield.
4. Remove the splash shield.
5. Carefully disconnect the vapor/vacuum/vent hoses (2).
6. Slide the EVAP canister (4) to the left, off of mounting bracket.
7. Disconnect the charcoal canister shutoff valve harness connector (1).
8. Depress the locking tab (2) to release charcoal canister shutoff valve (1).
9. While holding the lock tab (2) in release position, turn charcoal canister shutoff valve (1) clockwise and remove from EVAP canister.
10. Discard the old O-ring (3).

INSTALLATION - VAPOR CANISTER

1. Install the charcoal canister shutoff valve (1) to EVAP canister (2) using new O-ring (3).
2. Connect the charcoal canister shutoff valve harness connector (1).
3. Connect the hoses (2).
4. Slide the EVAP canister to the right, on to mounting bracket.
5. Install the splash shield and retaining nuts.
6. Lower the vehicle.
7. Connect the negative battery cable.

SPECIFICATIONS

TORQUE SPECIFICATIONS

Scheme 14

Scheme 15

1. Disconnect the negative battery cable.
2. Remove the air cleaner housing.
3. Disconnect the solenoid harness connector (1).
4. Disconnect the solenoid vacuum lines (2).
5. Remove the solenoid to valve mounting bolt (2).
6. Remove the valve to cylinder head mounting bolt (1).
7. Clean the gasket surfaces. Discard the old gasket.
8. Clean the EGR passages as necessary.

INSTALLATION - EGR SOLENOID

1. Position the solenoid to valve and loosely install solenoid to valve bolt (2).
2. Install the valve bolt (1) to cylinder head. Tighten to 31 N.m (23 ft. lbs.).
3. Tighten the solenoid to valve bolt (2) to 11 N.m (95 in. lbs.).
4. Connect the vacuum hoses (2).
5. Connect the EGR solenoid harness connector (1).
6. Install the air cleaner housing.
7. Connect the negative battery cable.

Scheme 16

1. Remove the air cleaner housing.
2. Remove the EGR tube mounting bolts (1) at the intake manifold.
3. Remove the EGR tube flange nut (2) at the EGR valve.
4. Remove the EGR tube.
5. Clean the gasket surfaces on the EGR tube and intake manifold. Discard old gasket.

Note. Any loose dirt can lodge between the tube and manifold and cause vacuum leakage that will give a rough idle and reduced manifold vacuum.

INSTALLATION - EGR TUBE

1. Loosely install the EGR tube flange nut (2) to the EGR valve.
2. Position the new gasket between tube and intake manifold.
3. Install the tube bolts (1) to intake manifold. Tighten to 31 N.m (23 ft. lbs.).
4. Tighten the EGR tube flange nut (2) to 11 N.m (95 in. lbs.).
5. Install the air cleaner housing.

Scheme 17

The EGR Valve consists of three major components

1. EGR Valve
2. EGR Solenoid
3. EGR Tube

The EGR Valve (3) is located at the right rear of the engine and is attached to the right cylinder head, to the right of the Throttle Body (4). The EGR Solenoid (2) is attached to the EGR Valve (3) on the throttle body side of the valve. The EGR Tube (1) connects the EGR Valve (3) to the rear of the Intake Manifold (5).

OPERATION - EGR VALVE

The Exhaust Gas Recirculation flow is determined by the Powertrain Control Module (PCM). For a given set of conditions, the PCM calculates the ideal exhaust gas recirculation flow to minimize NOx emissions and maximize fuel economy by adjusting the pintle position. Pintle position is controlled by the EGR Solenoid. The PCM adjusts the duty cycle of the power supplied to the solenoid coil to obtain the correct position.

Scheme 18

Scheme 19

1. Disconnect the negative battery cable.
2. Remove the air cleaner housing.
3. Disconnect the solenoid harness connector (1).
4. Disconnect the solenoid to valve vacuum line (2).
5. Remove the EGR tube flange nut (2) at valve.
6. Remove the solenoid to valve mounting bolt (3).
7. Remove the valve to cylinder head mounting bolts (1).
8. Clean the gasket surfaces. Discard the old gasket.
9. Clean the EGR passages as necessary.

Scheme 20

1. Position new gasket between the valve and cylinder head.
2. Loosely install valve front bolt (1) to cylinder head, do not tighten bolt.
3. Position solenoid to valve and loosely install solenoid (3) to valve bolt.
4. Loosely install valve rear bolt (2) to cylinder head, do not tighten bolt.
5. Loosely install the EGR tube flange nut (2) to valve.
6. Tighten the valve to cylinder head bolts (1) to 31 N.m (23 ft. lbs.).
7. Tighten the flange nut (2) to 11 N.m (95 in. lbs.).
8. Tighten the solenoid to valve bolt (3) to 11 N.m (95 in. lbs.).
9. Connect the solenoid harness connector (1).
10. Connect the vacuum hose (2).
11. Install the air cleaner housing.
12. Connect the negative battery cable.

Scheme 21

This vehicle is equipped with an Air Pump that injects air into the exhaust to reduce the emissions during engine warm-up. The air injected into the exhaust will cause the catalytic converters to heat up more quickly. This will improve the emission levels during a cold start. The Air Pump Switchover System incorporates an Air Pump (4) with two Air Pump Switchover Valves (1 and 6), an Air Pump Switchover Solenoid (3), an Air Pump Relay, a Vacuum Check Valve (5) and the PCM.

The Air Pump Relay is located in the Relay Control Module and can be easily identified by referring to the relay control module label. The Air Pump is mounted to the top center of the engine timing cover. The Air Pump Switchover valves (1 and 6) are located at the front, top of the engine, mounted just in front of the left and right cylinder covers. The Air Pump Switchover Solenoid (3) is mounted on the right front of the engine, just below the Air Pump Switchover Valve RH (6).

Scheme 22

Air is allowed to enter the exhaust when the PCM simultaneously actuates the Air Pump Relay, Air Pump (1), and Air Pump Switchover Solenoid (4) after engine start-up for up to 2 1/2 minutes. The following conditions must also be met in order for the system to become active

1. Coolant Temperature >10°C (50°F) but <60°C (140°F)
2. Engine Speed <3000 RPM
3. Throttle Valve Not Wide Open

After an actuation, the air injection system will remain deactivated until the coolant temperature drops from >60°C (140°F) to <40°C (104°F).

The Air Pump (1) draws in air through a maintenance-free filter and pumps it to the Air Pump Switchover Valves (3 and 6). The Air Pump Switchover Valves (3 and 6) prevent exhaust gases from flowing back into the Air Pump (1).

The Air Pump Switchover Solenoid (4) is supplied with vacuum from the intake manifold through a check valve (5). When the Air Pump Switchover Solenoid (4) is activated, it passes engine vacuum to the Air Pump Switchover Valves (3 and 6). The air which is delivered via the Air Pump Switchover Tube (2) is forced through the valves into the cylinder head openings to the exhaust. The injected air reacts with the hot exhaust gases in the outlet port. An oxidation of carbon monoxides (CO) and hydrocarbons (HC) takes place and results in an additional increase in the exhaust temperature.

SPECIFICATIONS - TORQUE

TORQUE SPECIFICATIONS

Scheme 23

Scheme 24

1. Disconnect the negative battery cable.
2. Remove the air cleaner housing.
3. Disconnect the air pump switchover tube (1).
4. Disconnect the air pump harness connector (2).
5. Remove the air pump retaining bolt (2).
6. Remove the air pump (1) from the air pump retaining bracket (3).

Scheme 25

Scheme 26

1. Position the air pump (1) into the air pump retaining bracket (3).
2. Install the air pump retaining bolt (2). Tighten bolt to 20 N.m (177 in. lbs.).
3. Connect the air pump harness connector (2).
4. Connect the air pump switchover tube (1).
5. Install the air cleaner housing.
6. Connect the negative battery cable.

Scheme 27

Scheme 28

1. Disconnect the negative battery cable.
2. Remove the air cleaner housing.
3. Disconnect the air pump switchover solenoid harness connector (2).
4. Disconnect the vacuum lines (1).
5. Pull the air pump switchover solenoid locking tab (1) away from air pump switchover solenoid (2).
6. Remove the air pump switchover solenoid (2) from air pump switchover solenoid retaining bracket (3).

INSTALLATION - SWITCHOVER SOLENOID

1. Position the air pump switchover solenoid (2) above air pump switchover solenoid mounting bracket (3) and lower until air pump switchover solenoid locking tab (1) snaps into place.
2. Connect the vacuum lines (1).
3. Connect the air pump switchover solenoid harness connector (2).
4. Install the air cleaner housing.
5. Connect the negative battery cable.

Scheme 29

1. Disconnect the negative battery cable.
2. Remove the air cleaner housing.
3. Disconnect the vacuum line (3).
4. Disconnect the air pump switchover tube (2).
5. Remove the air pump switchover valve retaining bolt (4).
6. Remove the air pump switchover valve (1) discard the old gasket.

INSTALLATION - SWITCHOVER VALVE

1. Position the new gasket between intake manifold and air pump switchover valve (1).
2. Install the retaining bolt (4). Tighten bolt to 20 N.m (177 in. lbs.).
3. Connect the vacuum line (3).
4. Connect the air pump switchover tube (2).
5. Install the air cleaner housing.
6. Connect the negative battery cable.

GLOSSARY OF TERMS

OBDII MONITOR RUN PROCESS

The following procedure has been established to assist technicians in the field with enabling and running OBD II Monitors. The order listed in the following procedure is intended to allow the technician to effectively complete each monitor and to set the CARB Readiness Status in the least time possible.

Note. Once the monitor run process has begun, do not turn off the ignition. By turning the ignition key off, monitor enabling conditions will be lost. EVAP Monitor runs after key off. By performing a Battery Disconnect, or Selecting Erase DTCs, the CARB Readiness and all additional OBD II information will be cleared.

Monitor Preliminary Checks

1. Plug a scan tool into the vehicle's Data Link Connector (DLC).
2. Turn the ignition, KEY ON - ENGINE OFF. Watch for MIL lamp illumination during the bulb check. MIL lamp must have illuminated, if not, repair MIL lamp.
3. Using a scan tool check for Powertrain related DTCs. Verify that No Emissions Related DTCs are Present. If an Emissions DTC is Present, the OBD II Monitors may not run and the CARB Readiness will not update. The Emissions related DTC, will need to be repaired, then cleared. By clearing DTCs, the OBD Monitors will need to be run and completed to set the CARB Readiness Status.

Using the scan tool check the CARB Readiness Status.

Do all the CARB Readiness Status Locations read YES?

1. YES - all monitors have been completed and this vehicle is ready to be I/M or Emission Tested.
2. NO - then the following procedure needs to be followed to run/complete all available monitors.

Note. Only the monitors, which are not YES in the CARB Readiness Status, need to be completed. Specific criteria need to be met for each monitor. The most efficient order to run the monitors has been outlined below, including suggestions to aid the process.

Evaporative Emission System Leak Detection with Purge Monitor

This monitor requires a cool down cycle, usually an overnight soak for at least 8 hours without the engine running. The ambient temperature must decrease overnight - parking the vehicle outside is advised. To run this test the fuel level must be between 15-85% full. Criteria for EVAP monitor

1. Engine off time greater than one hour.
2. Fuel Level between 15% and 85%.
3. Start Up ECT and IAT within 10°C (18°F).
4. Vehicle started and run until Purge Monitor reports a result.

Note. If the vehicle does not report a result and the conditions where correct. It may take up to two weeks to fail the small leak monitor. DO NOT use this test to attempt to determine a fault. Use the appropriate service information procedure for finding a small leak. If there are no faults and the conditions are correct this test will run and report a pass. Note the Small leak test can find leaks less than 10 thousands of an inch. If a small leak is present it takes approximately one week of normal driving to report a failure.

Catalyst/O2 Monitor

The Catalyst and O2 Monitor information are acquired and processed at the same time. Most vehicles will need to be driven at highway speed (less than 50 mph) (73 km/h) for a few minutes. Some vehicles run the monitor at idle in drive. If the vehicle is equipped with a manual transmission, using 4th gear may assist in meeting the monitor running criteria.

1. Engine RPM between 1200 to 3000.
2. Engine temperature greater than 70°C (158°F)
3. Engine run time greater than 92 seconds
4. MAP between 10 - 20 kPa (7.5 - 15 Hg)
5. Vehicle speed between 20 - 70 mph (29-103 km/h)

After the vehicle has reached the below conditions and during a throttle decel the EGR monitor will run.

1. Engine RPM between 1375 - 2500
2. Engine temperature greater than 70°C (158°F)
3. Engine run time greater than 125 seconds
4. Vehicle speed between 25 - 70 mph (37-103 km/h)

O2 Sensor Heater Monitor

This monitor is now continuously running once the heaters are energized. Pass information will be processed at power down.

The Misfire Monitor is a continuous two-trip monitor. The monitor uses two different tests/counters

Note. The Adaptive Numerator must be learned before the PCM will run the Misfire Monitor. The PCM updates the Adaptive Numerator at every key-ON, and is relearned after battery disconnect. The Misfire Monitor will not run until the Adaptive Numerator has updated since the last battery disconnect. If the Adaptive Numerator is equal to the default value then the PCM knows that the Adaptive Numerator has not been learned and does not permit the Misfire Monitor to run. If the Adaptive Numerator exceeds a calibrated percentage, the PCM sets a DTC for CKP NOT LEARNED and illuminates the MIL.

1. 200 Revolution Counter - Looks for misfire that can cause immediate catalyst damage.
2. 1000 Revolution Counter - Looks for misfire that can cause emissions to increase 1.5 times the Federal Test Procedure (FTP) standards. This test must also identify misfire percentages that might cause a "durability demonstration vehicle" to fail an Inspection and Maintenance Program tailpipe emissions test.

DESCRIPTION - TASK MANAGER

The PCM is responsible for efficiently coordinating the operation of all the emissions-related components. The PCM is also responsible for determining if the diagnostic systems are operating properly. The software designed to carry out these responsibilities is called the Task Manager.

OPERATION - TASK MANAGER

The Task Manager determines which tests happen when and which functions occur when. Many of the diagnostic steps required by OBD II must be performed under specific operating conditions. The Task Manager software organizes and prioritizes the diagnostic procedures. The job of the Task Manager is to determine if conditions are appropriate for tests to be run, monitor the parameters for a trip for each test, and record the results of the test. Following are the responsibilities of the Task Manager software

1. Test Sequence
2. MIL Illumination
3. Diagnostic Trouble Codes (DTCs)
4. Trip Indicator
5. Freeze Frame Data Storage
6. Similar Conditions Window

Test Sequence

In many instances, emissions systems must fail diagnostic tests more than once before the PCM illuminates the MIL. These tests are know as 'two trip monitors.' Other tests that turn the MIL lamp on after a single failure are known as 'one trip monitors.' A trip is defined as 'start the vehicle and operate it to meet the criteria necessary to run the given monitor.'

Many of the diagnostic tests must be performed under certain operating conditions. However, there are times when tests cannot be run because another test is in progress (Conflict), another test has failed (Pending) or the Task Manager has set a fault that may cause a failure of the test (Suspend).

1. Pending Under some situations, the Task Manager will not run a monitor if the MIL is illuminated and a fault is stored from another monitor. In these situations, the Task Manager postpones monitors Pending resolution of the original fault. The Task Manager does not run the test until the problem is remedied. For example, when the MIL is illuminated for an Oxygen Sensor fault, the Task Manager does not run the Catalyst Monitor until the Oxygen Sensor fault is remedied. Since the Catalyst Monitor is based on signals from the Oxygen Sensor, running the test would produce inaccurate results.
2. Conflict There are situations when the Task Manager does not run a test if another monitor is in progress. In these situations, the effects of another monitor running could result in an erroneous failure. If this Conflict is present, the monitor is not run until the conflicting condition passes. Most likely the monitor will run later after the conflicting monitor has passed. For example, if the Fuel System Monitor is in progress, the Task Manager does not run the EGR Monitor. Since both tests monitor changes in air/fuel ratio and adaptive fuel compensation, the monitors will conflict with each other.
3. Suspend Occasionally the Task Manager may not allow a two trip fault to mature. The Task Manager will Suspend the maturing of a fault if a condition exists that may induce an erroneous failure. This prevents illuminating the MIL for the wrong fault and allows more precise diagnosis. For example, if the PCM is storing a one trip fault for the Oxygen Sensor and the EGR monitor, the Task Manager may still run the EGR Monitor but will suspend the results until the Oxygen Sensor Monitor either passes or fails. At that point the Task Manager can determine if the EGR system is actually failing or if an Oxygen Sensor is failing.

MIL Illumination

The PCM Task Manager carries out the illumination of the MIL. The Task Manager triggers MIL illumination upon test failure, depending on monitor failure criteria.

The Task Manager Screen shows both a Requested MIL state and an Actual MIL state. When the MIL is illuminated upon completion of a test for a third trip, the Requested MIL state changes to OFF. However, the MIL remains illuminated until the next key cycle. During the key cycle for the third good trip, the Requested MIL state is OFF, while the Actual MIL state is ON. After the next key cycle, the MIL is not illuminated and both MIL states read OFF.

Diagnostic Trouble Codes (DTCs)

With OBD II, different DTC faults have different priorities according to regulations. As a result, the priorities determine MIL illumination and DTC erasure. DTCs are entered according to individual priority. DTCs with a higher priority overwrite lower priority DTCs.

Priorities

1. Priority 0 - Non-emissions related trouble codes
2. Priority 1 - One trip failure of a two trip fault for non-fuel system and non-misfire.
3. Priority 2 - One trip failure of a two trip fault for fuel system (rich/lean) or misfire.
4. Priority 3 - Two trip failure for a non-fuel system and non-misfire or matured one trip comprehensive component fault.
5. Priority 4 - Two trip failure or matured fault for fuel system (rich/lean) and misfire or one trip catalyst damaging misfire.

Non-emissions related failures have no priority. One trip failures of two trip faults have low priority. Two trip failures or matured faults have higher priority. One and two trip failures of fuel system and misfire monitor take precedence over non-fuel system and non-misfire failures.

DTC Self Erasure

With one trip components or systems, the MIL is illuminated upon test failure and DTCs are stored.

Two trip monitors are components requiring failure in two consecutive trips for MIL illumination. Upon failure of the first test, the Task Manager enters a maturing code. If the component fails the test for a second time the code matures and a DTC is set.

After three good trips the MIL is extinguished and the Task Manager automatically switches the trip counter to a warm-up cycle counter. DTCs are automatically erased following 40 warm-up cycles if the component does not fail again.

For misfire and fuel system monitors, the component must pass the test under a Similar Conditions Window in order to record a good trip. A Similar Conditions Window is when engine RPM is within ±375 RPM and load is within ±10% of when the fault occurred.

Note. It is important to understand that a component does not have to fail under a similar window of operation to mature. It must pass the test under a Similar Conditions Window when it failed to record a Good Trip for DTC erasure for misfire and fuel system monitors.

DTCs can be erased anytime with a scan tool. Erasing the DTC with the scan tool erases all OBD II information. The scan tool automatically displays a warning that erasing the DTC will also erase all OBD II monitor data. This includes all counter information for warm-up cycles, trips and Freeze Frame.

Trip Indicator

The Trip is essential for running monitors and extinguishing the MIL. In OBD II terms, a trip is a set of vehicle operating conditions that must be met for a specific monitor to run. All trips begin with a key cycle.

Good Trip

The Good Trip counters are as follows

1. Specific Good Trip
2. Fuel System Good Trip
3. Misfire Good Trip
4. Alternate Good Trip (appears as a Global Good Trip on scan tool)
5. Warm-up Cycles

Specific Good Trip

The term Good Trip has different meanings depending on the circumstances

1. If the MIL is OFF, a trip is defined as when the Oxygen Sensor Monitor and the Catalyst Monitor have been completed in the same drive cycle.
2. If the MIL is ON and a DTC was set by the Fuel Monitor or Misfire Monitor (both continuous monitors), the vehicle must be operated in the Similar Condition Window for a specified amount of time.
3. If the MIL is ON and a DTC was set by a Task Manager commanded once-per-trip monitor (such as the Oxygen Sensor Monitor, Catalyst Monitor, Purge Flow Monitor, Leak Detection Pump Monitor, EGR Monitor or Oxygen Sensor Heater Monitor), a good trip is when the monitor is passed on the next start-up.
4. If the MIL is ON and any other emissions DTC was set (not an OBD II monitor), a good trip occurs when the Oxygen Sensor Monitor and Catalyst Monitor have been completed, or two minutes of engine run time if the Oxygen Sensor Monitor and Catalyst Monitor have been stopped from running.

Fuel System Good Trip

To count a good trip (three required) and turn off the MIL, the following conditions must occur

1. Engine in closed loop
2. Operating in Similar Conditions Window
3. Short Term multiplied by Long Term less than threshold
4. Less than threshold for a predetermined time

If all of the previous criteria are met, the PCM will count a good trip (three required) and turn off the MIL.

Misfire Good Trip

If the following conditions are met the PCM will count one good trip (three required) in order to turn off the MIL

1. Operating in Similar Condition Window
2. 1000 engine revolutions with no misfire

Warm-up Cycles

Once the MIL has been extinguished by the Good Trip Counter, the PCM automatically switches to a Warm-up Cycle Counter that can be viewed on the scan tool. Warm-up Cycles are used to erase DTCs and Freeze Frames. Forty Warm-up cycles must occur in order for the PCM to self-erase a DTC and Freeze Frame. A Warm-up Cycle is defined as follows

1. Engine coolant temperature must start below and rise above 71°C (160°F)
2. Engine coolant temperature must rise by 4.4°C (40°F)
3. No further faults occur

Freeze Frame Data Storage

Once a failure occurs, the Task Manager records several engine operating conditions and stores it in a Freeze Frame. The Freeze Frame is considered one frame of information taken by an onboard data recorder. When a fault occurs, the PCM stores the input data from various sensors so that technicians can determine under what vehicle operating conditions the failure occurred.

The data stored in Freeze Frame is usually recorded when a system fails the first time for two trip faults. Freeze Frame data will only be overwritten by a different fault with a higher priority.

Note. Erasing DTCs, either with the scan tool or by disconnecting the battery, also clears all Freeze Frame data.

Similar Conditions Window

The Similar Conditions Window displays information about engine operation during a monitor. Absolute MAP (engine load) and Engine RPM are stored in this window when a failure occurs. There are two different Similar conditions Windows: Fuel System and Misfire.

FUEL SYSTEM

1. Fuel System Similar Conditions Window - An indicator that 'Absolute MAP When Fuel Sys Fail' and 'RPM When Fuel Sys Failed' are all in the same range when the failure occurred. Indicated by switching from 'NO' to 'YES'.
2. Absolute MAP When Fuel Sys Fail - The stored MAP reading at the time of failure. Informs the user at what engine load the failure occurred.
3. Absolute MAP - A live reading of engine load to aid the user in accessing the Similar Conditions Window.
4. RPM When Fuel Sys Fail - The stored RPM reading at the time of failure. Informs the user at what engine RPM the failure occurred.
5. Engine RPM - A live reading of engine RPM to aid the user in accessing the Similar Conditions Window.
6. Adaptive Memory Factor - The PCM utilizes both Short Term Compensation and Long Term Adaptive to calculate the Adaptive Memory Factor for total fuel correction.
7. Upstream O2S Volts - A live reading of the Oxygen Sensor to indicate its performance. For example, stuck lean, stuck rich, etc.
8. SCW Time in Window (Similar Conditions Window Time in Window) - A timer used by the PCM that indicates that, after all Similar Conditions have been met, if there has been enough good engine running time in the SCW without failure detected. This timer is used to increment a Good Trip.
9. Fuel System Good Trip Counter - A Trip Counter used to turn OFF the MIL for Fuel System DTCs. To increment a Fuel System Good Trip, the engine must be in the Similar Conditions Window, Adaptive Memory Factor must be less than the calibrated threshold and the Adaptive Memory Factor must stay below that threshold for a calibrated amount of time.
10. Test Done This Trip - Indicates that the monitor has already been run and completed during the current trip.

MISFIRE

1. Same Misfire Warm-Up State - Indicates if the misfire occurred when the engine was warmed up above 71°C (160°F).
2. In Similar Misfire Window - An indicator that 'Absolute MAP When Misfire Occurred' and 'RPM When Misfire Occurred' are all in the same range when the failure occurred. Indicated by switching from 'NO' to 'YES'.
3. Absolute MAP When Misfire Occurred - The stored MAP reading at the time of failure. Informs the user at what engine load the failure occurred.
4. Absolute MAP - A live reading of engine load to aid the user in accessing the Similar Conditions Window.
5. RPM When Misfire Occurred - The stored RPM reading at the time of failure. Informs the user at what engine RPM the failure occurred.
6. Engine RPM - A live reading of engine RPM to aid the user in accessing the Similar Conditions Window.
7. Adaptive Memory Factor - The PCM utilizes both Short Term Compensation and Long Term Adaptive to calculate the Adaptive Memory Factor for total fuel correction.
8. 200 Rev Counter - Counts 0-100 720 degree cycles.
9. SCW Cat 200 Rev Counter - Counts when in similar conditions.
10. SCW FTP 1000 Rev Counter - Counts 0-4 when in similar conditions.
11. Misfire Good Trip Counter - Counts up to three to turn OFF the MIL.
12. Misfire Data - Data collected during test.
13. Test Done This Trip - Indicates YES when the test is done.

See also:
• FUEL DELIVERY
• DESCRIPTION - MONITORED SYSTEMS
• DESCRIPTION - MONITORED COMPONENTS
• DESCRIPTION - NON-MONITORED SYSTEMS