Emissions Control: Other Dodge Challenger III facelift

VEHICLE EMISSION CONTROL INFORMATION LABEL

All models have a Vehicle Emission Control Information (VECI) Label. Chrysler 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 model year and what regulations the vehicle conforms to and if the vehicle is OBD II compliant.

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 Malfunction Indicator Lamp (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 40° F (4.4° C) in engine temperature must occur from the time when the engine was started
3. Engine coolant temperature must crossover 160° F (71° C)
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 DTC's be erased and the repair verified by running 1 good trip.

NON-MONITORED CIRCUITS

The PCM does not monitor all circuits, systems and conditions that could have malfunctions causing driveability problems. However, problems with 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 failures modes that do not directly cause the PCM to set a DTC but 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 in to thinking the fuel system is too lean. Also see misfire detection. There are DTC's that can detect misfire and Ionization shorts in the secondary ignition circuit, refer to the appropriate Powertrain Diagnostic for more information.

CYLINDER COMPRESSION

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

EXHAUST SYSTEM

The PCM cannot detect a plugged, restricted or leaking exhaust system. It may set a EGR (if equipped) or 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, 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. 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. The module should be mounted to the body at all times, including when diagnostics are performed.

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 spread connector pins.

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 appropriate Diagnostic Trouble Codes Description Charts in this information and the appropriate Powertrain Diagnostic Procedure Information for diagnostic procedures.

The following is a list of the monitored components

1. Catalyst Monitor
2. Comprehensive Components
3. EGR (if equipped)
4. Fuel Control (rich/lean)
5. O2S sensor Monitor
6. O2S sensor Heater Monitor
7. Purge
8. Misfire
9. 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 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 include

Circuit Continuity

1. Open
2. Shorted high
3. Shorted to ground

Rationality or Proper Functioning

1. Inputs tested for rationality
2. 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

1. Manifold Absolute Pressure (MAP) Sensor
2. O2S sensor (O2S) (slow response)
3. Engine Coolant Temperature (ECT) Sensor
4. Camshaft Position (CMP) Sensor
5. Vehicle Speed Sensor
6. Crankshaft Position (CKP) Sensor
7. Intake Air Temperature (IAT) Sensor
8. Throttle Position (TPS) Sensor
9. Ambient/Battery Temperature Sensors
10. Power Steering Switch
11. O2S sensor Heater
12. Engine Controller
13. Brake Switch
14. Evaporative System Integrity Monitor (ESIM)
15. PRNDL 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 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

1. Fuel Injectors
2. Ignition Coils
3. Torque Converter Clutch Solenoid
4. Idle Air Control
5. Purge Solenoid
6. EGR Solenoid
7. Radiator Fan Control
8. Trans Controls

O2S 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° C to 350° C (572° F 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 450 mV.

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

1. Slow response rate (Big Slope)
2. Reduced output voltage (Half Cycle)
3. 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 O2S sensor experiences is called 'Big Slope'. The PCM checks the O2S 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 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.

Heater Performance- The heater is tested by a separate monitor. Refer to O2S SENSOR HEATER MONITOR (NGC) .

Operation- As the O2S sensor signal switches, the PCM monitors the half cycle and big slope signals from the O2S 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 O2S sensor Signal Monitor is a two trip monitor that is tested only once per trip. When the O2S sensor fails the test in two consecutive trips, the MIL is illuminated and a DTC is set. The MIL is extinguished when the O2S 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 O2S sensor monitor

1. Battery voltage
2. Engine temperature
3. Engine run time
4. Engine run time at a predetermined speed
5. Engine run time at a predetermined speed and throttle opening
6. Transmission in gear (automatic only)
7. Fuel system in Closed Loop
8. Long Term Adaptive (within parameters)
9. Power Steering Switch in low PSI (no load)
10. Engine at idle
11. Fuel level above 15%
12. Ambient air temperature
13. Barometric pressure
14. Engine RPM within acceptable range of desired idle
15. Closed throttle speed

Pending Conditions- The Task Manager typically does not run the O2S sensor Signal Monitor if overlapping monitors are running or the MIL is illuminated for any of the following

1. Misfire Monitor
2. Front O2S sensor and Heater Monitor
3. MAP Sensor
4. Vehicle Speed Sensor
5. Engine Coolant Temperature Sensor
6. Throttle Position Sensor
7. Engine Controller Self Test Faults
8. Cam or Crank Sensor
9. Injector and Coil
10. Idle Air Control Motor
11. EVAP Electrical
12. EGR Solenoid Electrical
13. Intake Air Temperature
14. 5 Volt Feed

Conflict- The Task Manager does not run the O2S sensor Monitor if any of the following conditions are present

1. A/C ON (A/C clutch cycling temporarily suspends monitor)
2. Purge flow in progress
3. Ethanol content learn is taking place and the ethanol used once flag is set

Suspend- The Task Manager suspends maturing a fault for the O2S sensor Monitor if an of the following are present

1. O2S sensor Heater Monitor, Priority 1
2. Misfire Monitor, Priority 2

O2S SENSOR HEATER MONITOR (NGC)

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

The voltage reading taken from the O2S sensor are very temperature sensitive. The readings taken from the O2S sensor are not accurate below 300° C (572° F). Heating the O2S sensor 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 sensor must be tested to ensure that it is heating the sensor properly. Starting with the introduction on the NGC module the strategy for checking the heater circuit has changed. The O2S sensor heater resistance is checked by the NGC almost immediately after the engine is started. The same O2S sensor heater return pin used to read the O2S sensor heater resistance is capable of detecting an open circuit, a shorted high or shorted low condition.

CATALYST MONITOR

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 reduction of the exhaust passage. This can increase vehicle emissions and deteriorate engine performance, driveability and fuel economy.

The catalyst monitor uses dual O2S sensors to monitor the efficiency of the converter. The dual O2S sensors 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 A/F mixture from the output of the O2S sensors. A low voltage indicates high oxygen content (lean mixture). A high voltage indicates a low content of oxygen (rich mixture).

When the upstream O2S sensors 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 sensors 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 sensors. 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 sensors copy the voltage of the upstream sensors. The only difference is a time lag (seen by the PCM) between the switching of the O2S sensors.

To monitor the system, the number of lean-to-rich switches of upstream and downstream O2S sensors 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 (check engine lamp) will be illuminated.

Monitor Operation- To monitor catalyst efficiency, the PCM expands the rich and lean switch points of the heated O2S 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 O2 switches are counted. A switch is counted when an O2S sensor signal goes from below the lean threshold to above the rich threshold. The number of Rear O2 sensor switches is divided by the number of Front O2 sensor switches to determine the switching ratio.

The test runs for 20 seconds. As catalyst efficiency deteriorated 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. The good trip criteria for the catalyst monitor is more stringent than the failure criteria. In order to pass the test and increment one good trip, the downstream sensor switch rate must be less than 80% of the upstream rate (60% for manual transmissions). The failure percentages are 90% and 70% respectively.

Enabling Conditions- The following conditions must typically be met before the PCM runs the catalyst monitor. Specific times for each parameter may be different from engine to engine.

1. Accumulated drive time
2. Enable time
3. Ambient air temperature
4. Barometric pressure
5. Catalyst warm-up counter
6. Engine coolant temperature
7. Accumulated throttle position sensor
8. Vehicle speed
9. MAP
10. RPM
11. Engine in closed loop
12. Fuel level

Pending Conditions- The Task Manager typically does not run the catalyst monitor if overlapping monitors are running or the MIL is illuminated for any of the following

1. Misfire DTC
2. Front O2S sensor Response
3. Front O2S sensor Heater Monitor
4. Front O2S sensor Electrical
5. Rear O2S sensor Rationality (middle check)
6. Rear O2S sensor Heater Monitor
7. Rear O2S sensor Electrical
8. Fuel System Monitor
9. All TPS faults
10. All MAP faults
11. All ECT sensor faults
12. Purge flow solenoid functionality
13. Purge flow solenoid electrical
14. All PCM self test faults
15. All CMP and CKP sensor faults
16. All injector and ignition electrical faults
17. Idle Air Control (IAC) motor functionality
18. Vehicle Speed Sensor
19. Brake switch
20. Intake air temperature

Conflict- The catalyst monitor does not run if any of the following are conditions are present

1. EGR Monitor in progress
2. Fuel system rich intrusive test in progress
3. EVAP Monitor in progress
4. Time since start is less than 60 seconds
5. Low fuel level
6. Low ambient air temperature
7. Ethanol content learn is taking place and the ethanol used once flag is set

Suspend- The Task Manager does not mature a catalyst fault if any of the following are present

1. O2S sensor Monitor, Priority 1
2. Upstream O2S sensor Heater, Priority 1
3. EGR Monitor, Priority 1
4. EVAP Monitor, Priority 1
5. Fuel System Monitor, Priority 2
6. Misfire Monitor, Priority 2

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 systems 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 (Check Engine) Lamp will be illuminated. These monitors generate a Diagnostic Trouble Codes (DTC) that can be displayed with a scan tool.

The following is a list of the system monitors

1. EGR Monitor (if equipped)
2. Misfire Monitor
3. Fuel System Monitor
4. Oxygen Sensor Monitor
5. Oxygen Sensor Heater Monitor
6. Catalyst Monitor
7. Evaporative System Integrity Monitor

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

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

OXYGEN SENSOR (O2S) MONITOR

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 temperatures of 572° F to 662° F (300° C to 350° C), the sensor generates a voltage that is inversely proportional to the amount of oxygen in the exhaust. 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 (if equipped), Catalyst and Fuel Monitors.

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

1. Slow response rate
2. Reduced output voltage
3. Dynamic shift
4. Shorted or open circuits

Response rate is the time required for the sensor to switch from lean to rich once it is exposed to a richer than optimum A/F mixture or vice versa. As the sensor starts malfunctioning, it could take longer to detect the changes in the oxygen content of the exhaust gas.

The output voltage of the O2S ranges from 0 to 1 volt (voltages are offset by 2.5 volts on NGC vehicles). 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.

OXYGEN SENSOR HEATER MONITOR

If there is an oxygen sensor (O2S) DTC as well as a O2S heater DTC, the O2S heater fault MUST be repaired first. After the O2S fault is repaired, verify that the heater circuit is operating correctly.

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 temperatures of 572° F to 662° F (300° C to 350° C), the sensor generates a voltage that is inversely proportional to the amount of oxygen in the exhaust. The information obtained by the sensor is used to calculate the fuel injector pulse width. This maintains a 14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio, the catalyst works best to remove hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide (NOx) from the exhaust.

The voltage readings taken from the O2S are very temperature sensitive. The readings are not accurate below 572° F (300° C). Heating of 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 O2S circuit is monitored for a drop in voltage. The sensor output is used to test the heater by isolating the effect of the heater element on the O2S output voltage from the other effects.

EGR MONITOR (IF EQUIPPED)

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 Linear solenoid is de-energized to disable EGR and the O2S compensation control is monitored. Turning off the EGR shifts the air fuel (A/F) 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.

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.

The PCM can detect and compensate for variances in the engine and its components. To learn these variations, the PCM uses the input of the actual crankshaft rotation pattern and ideal crankshaft rotation pattern that has been calibrated into the PCM. The PCM then compares the two patterns. The variation between the two values is the Adaptive Numerator. If the Adaptive Numerator is not learned by the PCM, the misfire monitor will not run and the Multi-Cylinder Displacement System (MDS) will not operate. Without MDS operation, the customer will experience decreased fuel economy. If the customer experiences decrease fuel economy, use the scan tool to ensure that the Adaptive Numerator is learned.

FUEL SYSTEM MONITOR

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. The catalyst works best when the air fuel (A/F) ratio is at or near the optimum of 14.7 to 1.

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 and 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 A/F ratio, then the MIL will be illuminated.

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 reduction of the exhaust passage. This can increase vehicle emissions and deteriorate engine performance, driveability and fuel economy.

The catalyst monitor uses dual oxygen sensors (O2S's) to monitor the efficiency of the converter. The dual O2S's 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 A/F 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 lean 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 O2S's.

To monitor the system, the number of lean-to-rich switches of upstream and downstream O2S's 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 (Check Engine lamp) will be illuminated.

EVAPORATIVE SYSTEM INTEGRITY MONITOR (ESIM)

The Evaporative System Integrity Monitor (ESIM) is very similar to the NVLD. However, the design of the ESIM has been simplified and unlike the NVLD the ESIM does not require a solenoid. The ESIM mounts directly to the vapor canister, eliminating the need for a mounting bracket. It is critical that the ESIM is mounted vertically. On vehicles where the canister is mounted on an angle, the ESIM requires an adaptor to maintain a vertical position. When the ESIM is installed vertically, the electrical connector is in the 3 o'clock position.

The ESIM consists of the following components

1. Diaphragm
2. Switch
3. Small Check Valve (small weight)
4. Large Check Valve (large weight)

There is one large weight and one small weight (check valves) in the ESIM assembly. A seal is attached at the end of each weighted check valve. The large weight check valve seals for pressure. The small weight check valve seals for vacuum. The weighted check valves are contained within the ESIM housing.

During refueling, pressure is built up in the evaporative system. When pressure reaches approximately.5 inches of water, the large check valve unseats and pressure vents to the fresh air filter.

Conversely, when the system cools, and the resulting vacuum lifts the small check valve from its seat and allows fresh air to enter the system through the fresh air inlet and relieves the vacuum condition. When a calibrated amount of vacuum is achieved in the evaporative system, the diaphragm is pulled inward, pushing on the spring and closing the contacts.

The ESIM conducts test on the evaporative system as follows: An engine off, non-intrusive test for small leaks and an engine running, intrusive test for medium/large leaks.

The ESIM weights seal the evaporative system during engine off conditions. If the evaporative system is sealed, it will be pulled into a vacuum, either due to the cool down from operating temperature or diurnal ambient temperature cycling. When the vacuum in the system exceeds about 1" H20, the vacuum switch closes. The switch closure sends a signal to the PCM. In order to pass the non-intrusive small leak test, the ESIM switch must close within a calculated amount of time and within a specified amount of key-off events.

If the ESIM switch does not close as specified, the test is considered inconclusive and the intrusive engine running test will be run during the next key-on cycle. This intrusive test will run on the next cold engine running condition.

Conditions for running the intrusive test are

1. After the vehicle is started, the engine coolant temperature must be within 50° F (10° C) of ambient to indicate a cold start.
2. The fuel level must be between 12% and 88%.
3. The engine must be in closed loop.
4. Manifold vacuum must be greater than a minimum specified value.
5. Ambient temperature must be between 39° F and 98° F (4° C and 37° C) and the elevation level must be below 8500 feet (2591 meters).

The test is accomplished by the PCM activating the purge solenoid to create a vacuum in the evaporative system. The PCM then measures the amount of time it takes for the vacuum to dissipate. This is known as the vacuum decay method. If the switch opens quickly a large leak is recorded. If the switch opens after a predetermined amount of time, then the small leak matures. If the switch does not close, then a general evaporative failure is recorded. The purge monitor tests the integrity of the hose attached between the purge valve and throttle body/intake. The purge monitor is a two stage test and it runs only after the evaporative system passes the small leak test.

Even when all of the thresholds are met, a small leak won't be recorded until after the medium/large leak monitor has been run. This is accomplished by the PCM activating the purge solenoid to create a vacuum in the evaporative system. The PCM then measures the amount of time it takes for the vacuum to dissipate. This is known as the vacuum decay method. If the switch opens quickly a large leak is recorded. If the switch opens after a predetermined amount of time, then the small leak matures. If the medium/large leak test runs and the ESIM switch doesn't close, a general evaporative test is run. The purge solenoid is activated for approximately 10 seconds, increasing the amount of vacuum in the system. If the ESIM switch closes after the extended purge activation, a large leak fault is generated. If the switch doesn't close, a general evaporative system fault is generated.

The purge monitor tests the integrity of the hose attached between the purge valve and throttle body/intake. The purge monitor is a two stage test and it runs only after the evaporative system passes the small leak test.

Stage one of the purge monitor is non-intrusive. The PCM monitors the purge vapor ratio. If the ratio is above a calibrated specification, the monitor passes. Stage two is an intrusive test and it runs only if stage one fails. During the stage two test, the PCM commands the purge solenoid to flow at a specified rate to force the purge vapor ratio to update. The vapor ratio is compared to a calibrated specification and if it is less than specified, a one-trip failure is recorded.

The ESIM switch stuck closed monitor checks to see if the switch is stuck closed. This is a power down test that runs at key-off; when the PCM sees 0 RPM's, the purge solenoid is energized for a maximum of 30 seconds, venting any vacuum trapped in the evaporative system. If the switch opens or was open before the test began, the monitor passes. If the switch doesn't open, the monitor fails. This is a two-trip MIL. The star scan tool can be used to force the ESIM switch stick closed monitor to run.

The PCM also uses the ESIM to detect a loose or missing gas cap. The PCM controller looks for a change in the fuel level (25% minimum) and then looks for a loose or missing gas cap. If a medium/large leak is detected, a loose gas cap light illuminates and a pending one-trip fault code is set. On the PCM, this is a three-trip fault before the code matures.

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). Refer to MIL ILLUMINATION .

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 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 DTC's. Refer to MONITORED COMPONENT , and NON-MONITORED CIRCUITS .

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 DTC's and extinguish the MIL.

Technicians can display stored DTC's. For obtaining the DTC information, use the Data Link Connector with the scan tool.

3.6L

The EVAP purge Solenoid (1) attaches to a bracket near the right rear of the engine. The solenoid will not operate unless it is installed correctly.

1. Install the EVAP purge solenoid (1) onto the mounting bracket.
2. Connect the vacuum lines (3, 5) to the EVAP purge solenoid.
3. Connect the electrical connector (2) to the EVAP purge solenoid.

6.4L

The PCV valve (1) is located at the top right rear of the intake manifold.

1. The PCV valve is sealed to the intake manifold with two O-rings (2).
2. Remove the PCV valve by rotating counterclockwise 90 degrees until the locating tabs (3) have been released.
3. Pull the PCV valve straight up and remove from the intake manifold.
4. Check the condition of the two PCV valve O-rings (2), replace if necessary.

1. Clean and inspect the sealing surfaces of the PCV valve and cylinder head cover. The seal can be reused provided it is free of cuts or tears.
2. Install the PCV valve seal in the cylinder head cover.
3. Install the PCV valve (1) with three screws (2). Tighten the screws to 4 N.m (35 in. lbs.).
4. Install the PCV hose (1) between the upper intake manifold and the PCV valve (2).

5.7L

1. Check the condition of the two PCV valve O-rings (2), replace if necessary.
2. Clean the PCV valve mounting surface of the intake manifold opening.
3. Apply engine oil to the two O-rings (2) on the PCV valve.
4. Position the PCV valve (1) into intake manifold and rotate 90 degrees clockwise until the locating tabs are locked in place.

1. Check the condition of the two PCV valve O-rings (2), replace if necessary.
2. Clean the PCV valve mounting surface of the intake manifold opening.
3. Apply engine oil to the two O-rings (2) on the PCV valve.
4. Position the PCV valve (1) into intake manifold and rotate 90 degrees clockwise until the locating tabs are locked in place.

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 the MIL lamp to illuminate during the bulb check. The MIL lamp must have illuminat. If not, repair the MIL lamp.
3. Using a scan tool check for Powertrain related DTCs.

1. Verify that no emissions-related DTCs are present. If an emissions-related DTC is present, the OBD II monitors may not run and the CARB Readiness will not update.
2. The emissions-related DTC needs to be repaired and then cleared. By clearing DTCs, the OBD monitors must be run and completed to set the CARB Readiness Status.

Using a scan tool check the CARB Readiness Status.

Do all of 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 complete the monitors, which are not YES in the CARB Readiness Status. 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 is a follows

1. Engine off time greater than one hour
2. Fuel Level between 15% and 85%
3. Start Up ECT and IAT within 10 degrees C (18 degrees F) of each other
4. Vehicle run until the 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 need to be driven at highway speed (less than 50 mph (73km/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)

EXHAUST GAS RECIRCULATION (EGR)

After the vehicle has reached the conditions listed below, and during a throttle deceleration, 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 is 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 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 also identifies misfire percentages that might cause a durability demonstration vehicle to fail an Inspection and Maintenance Program tailpipe emissions test.

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.

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 catalyst monitor. Since both tests monitor changes in air/fuel ratio and adaptive fuel compensation, the monitors will conflict with each other.

SUSPEND

Occasionally the Task Manager may not allow a two trip fault to mature. The Task Manager suspends 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 catalyst monitor, the Task Manager may still run the catalyst monitor but suspends the results until the oxygen sensor monitor either passes or fails. At that point the task manager can determine if the catalyst 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 good trip, the Requested MIL state changes to OFF. However, the MIL remains illuminated until the next key cycle (On some vehicles, the MIL will actually turn OFF during the third good trip.) 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.

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. Global Good Trip
2. Fuel System Good Trip
3. Misfire Good Trip
4. Alternate Good Trip (appears as a Global Good Trip on scan tool) Comprehensive Components Major Monitor
5. Warm-Up Cycles

Global Good Trip

To increment a Global Good Trip, the Oxygen sensor and catalyst efficiency monitors must have run and passed and 2 minutes of engine run time.

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 counts 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

Alternate Good Trip

Alternate Good Trips are used in place of Global Good Trips for comprehensive components and major monitors. If the Task Manager cannot run a Global Good Trip because a component fault is stopping the monitor from running, it will attempt to count an Alternate Good Trip.

The Task Manager counts an Alternate Good Trip for comprehensive components when the following conditions are met

1. two minutes of engine run time, idle or driving
2. no other faults occur

The Task Manager counts an Alternate Good Trip for a major monitor when the monitor runs and passes. Only the Major Monitor that failed needs to pass to count an Alternate Good Trip.

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 data. A Warm-Up Cycle is defined as follows

1. engine coolant temperature must start below and rise above 160°F (71°C)
2. engine coolant temperature must rise by 40° F (4.5° C)
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 data. The freeze frame is considered one frame of information taken by an on-board data recorder. When a fault occurs, the PCM stores the input data from various sensors so 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.

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 uses 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 or rich, etc.
8. SCW Time in Window (Similar Conditions Window Time in Window) - A timer used by the PCM that indicates, 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 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 71 degrees C (160 degrees 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 uses 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.