Emissions Control 25 - 1

TJ EMISSIONS CONTROL 25 - 1

EMISSIONS CONTROL

TABLE OF CONTENTS

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EMISSIONS CONTROL DESCRIPTION - TASK MANAGER ...... 2 DESCRIPTION DESCRIPTION - MONITORED SYSTEMS ....2 DESCRIPTION - EMISSION CONTROL DESCRIPTION - TRIP DEFINITION ...... 4 SYSTEM ...... 1 DESCRIPTION - COMPONENT MONITORS . . 5 DESCRIPTION - STATE DISPLAY TEST DESCRIPTION - NON-MONITORED MODE ...... 2 CIRCUITS ...... 5 DESCRIPTION - CIRCUIT ACTUATION TEST DESCRIPTION - HIGH AND LOW LIMITS ....6 MODE ...... 2 DESCRIPTION - LOAD VALUE ...... 6 DESCRIPTION - DIAGNOSTIC TROUBLE OPERATION - TASK MANAGER ...... 6 CODES ...... 2 EVAPORATIVE EMISSIONS ...... 10

EMISSIONS CONTROL There are several operating conditions for which the PCM monitors and sets DTC’s. Refer to Moni- tored Systems, Components, and Non-Monitored Cir- DESCRIPTION cuits in this section. Technicians must retrieve stored DTC’s by connect- DESCRIPTION - EMISSION CONTROL SYSTEM ing the DRB scan tool (or an equivalent scan tool) to The Powertrain Control Module (PCM) monitors the 16–way data link connector (Fig. 1). many different circuits in the fuel injection, ignition, emission and engine systems. If the PCM senses a NOTE: Various diagnostic procedures may actually problem with a monitored circuit often enough to cause a diagnostic monitor to set a DTC. For indicate an actual problem, it stores a Diagnostic instance, pulling a spark plug wire to perform a Trouble Code (DTC) in the PCM’s memory. If the spark test may set the misfire code. When a repair code applies to a non-emissions related component or is completed and verified, connect the DRB scan system, and the problem is repaired or ceases to tool to the 16–way data link connector to erase all exist, the PCM cancels the code after 40 warm-up DTC’s and extinguish the MIL. cycles. Diagnostic trouble codes that affect vehicle emissions illuminate the Malfunction Indicator Lamp (MIL). The MIL is displayed as an engine icon on the instrument panel. Refer to Malfunction Indicator Lamp (MIL) in this section. 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 Fig. 1 DATA LINK (DIAGNOSTIC) CONNECTOR PCM will not store a DTC. LOCATION 1 - 16–WAY DATA LINK CONNECTOR 25 - 2 EMISSIONS CONTROL TJ EMISSIONS CONTROL (Continued) DESCRIPTION - STATE DISPLAY TEST MODE (6) To erase DTC’s, use the “Erase Trouble Code” The switch inputs to the Powertrain Control Mod- data screen on the DRB scan tool. Do not erase any ule (PCM) have two recognized states; HIGH and DTC’s until problems have been investigated LOW. For this reason, the PCM cannot recognize the and repairs have been performed. difference between a selected switch position versus an open circuit, a short circuit, or a defective switch. DESCRIPTION - TASK MANAGER If the State Display screen shows the change from The PCM is responsible for efficiently coordinating HIGH to LOW or LOW to HIGH, assume the entire the operation of all the emissions-related compo- switch circuit to the PCM functions properly. Connect nents. The PCM is also responsible for determining if the DRB scan tool to the data link connector and the diagnostic systems are operating properly. The access the state display screen. Then access either software designed to carry out these responsibilities State Display Inputs and Outputs or State Display is referred to as the ’Task Manager’. Sensors. DESCRIPTION - MONITORED SYSTEMS DESCRIPTION - CIRCUIT ACTUATION TEST There are new electronic circuit monitors that MODE check fuel, emission, engine and ignition perfor- The Circuit Actuation Test Mode checks for proper mance. These monitors use information from various operation of output circuits or devices the Powertrain sensor circuits to indicate the overall operation of the Control Module (PCM) may not internally recognize. fuel, engine, ignition and emission systems and thus The PCM attempts to activate these outputs and the emissions performance of the vehicle. allow an observer to verify proper operation. Most of The fuel, engine, ignition and emission systems the tests provide an audible or visual indication of monitors do not indicate a specific component prob- device operation (click of relay contacts, fuel spray, lem. They do indicate that there is an implied prob- etc.). Except for intermittent conditions, if a device lem within one of the systems and that a specific functions properly during testing, assume the device, problem must be diagnosed. its associated wiring, and driver circuit work cor- If any of these monitors detect a problem affecting rectly. Connect the DRB scan tool to the data link vehicle emissions, the Malfunction Indicator Lamp connector and access the Actuators screen. (MIL) will be illuminated. These monitors generate Diagnostic Trouble Codes that can be displayed with DESCRIPTION - DIAGNOSTIC TROUBLE CODES the MIL or a scan tool. The following is a list of the system monitors: A Diagnostic Trouble Code (DTC) indicates the • Misfire Monitor PCM has recognized an abnormal condition in the • Fuel System Monitor system. • Oxygen Sensor Monitor Remember that DTC’s are the results of a sys- • Oxygen Sensor Heater Monitor tem or circuit failure, but do not directly iden- • Catalyst Monitor tify the failed component or components. • Leak Detection Pump Monitor (if equipped) BULB CHECK All these system monitors require two consecutive trips with the malfunction present to set a fault. Each time the ignition key is turned to the ON Refer to the appropriate Powertrain Diagnos- position, the malfunction indicator (check engine) tics Procedures manual for diagnostic proce- lamp on the instrument panel should illuminate for dures. approximately 2 seconds then go out. This is done for The following is an operation and description of a bulb check. each system monitor: OBTAINING DTC’S USING DRB SCAN TOOL OXYGEN SENSOR (O2S) MONITOR (1) Obtain the applicable Powertrain Diagnostic Effective control of exhaust emissions is achieved Manual. by an oxygen feedback system. The most important (2) Obtain the DRB Scan Tool. element of the feedback system is the O2S. The O2S (3) Connect the DRB Scan Tool to the data link is located in the exhaust path. Once it reaches oper- (diagnostic) connector. This connector is located in ating temperature 300° to 350°C (572° to 662°F), the the passenger compartment; at the lower edge of sensor generates a voltage that is inversely propor- instrument panel; near the steering column. tional to the amount of oxygen in the exhaust. The (4) Turn the ignition switch on and access the information obtained by the sensor is used to calcu- “Read Fault” screen. late the fuel injector pulse width. This maintains a (5) Record all the DTC’s and “freeze frame” infor- 14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio, mation shown on the DRB scan tool. TJ EMISSIONS CONTROL 25 - 3 EMISSIONS CONTROL (Continued) the catalyst works best to remove hydrocarbons (HC), LEAK DETECTION PUMP MONITOR (IF EQUIPPED) carbon monoxide (CO) and nitrogen oxide (NOx) from The leak detection assembly incorporates two pri- the exhaust. mary functions: it must detect a leak in the evapora- The O2S is also the main sensing element for the tive system and seal the evaporative system so the Catalyst and Fuel Monitors. leak detection test can be run. The O2S can fail in any or all of the following The primary components within the assembly are: manners: A three port solenoid that activates both of the func- • slow response rate tions listed above; a pump which contains a switch, • reduced output voltage two check valves and a spring/diaphragm, a canister • dynamic shift vent valve (CVV) seal which contains a spring loaded • shorted or open circuits vent seal valve. Response rate is the time required for the sensor to Immediately after a cold start, between predeter- switch from lean to rich once it is exposed to a richer mined temperature thresholds limits, the three port than optimum A/F mixture or vice versa. As the sen- solenoid is briefly energized. This initializes the sor starts malfunctioning, it could take longer to pump by drawing air into the pump cavity and also detect the changes in the oxygen content of the closes the vent seal. During non test conditions the exhaust gas. vent seal is held open by the pump diaphragm The output voltage of the O2S ranges from 0 to 1 assembly which pushes it open at the full travel posi- volt. A good sensor can easily generate any output tion. The vent seal will remain closed while the voltage in this range as it is exposed to different con- pump is cycling due to the reed switch triggering of centrations of oxygen. To detect a shift in the A/F the three port solenoid that prevents the diaphragm mixture (lean or rich), the output voltage has to assembly from reaching full travel. After the brief change beyond a threshold value. A malfunctioning initialization period, the solenoid is de-energized sensor could have difficulty changing beyond the allowing atmospheric pressure to enter the pump threshold value. cavity, thus permitting the spring to drive the diaphragm which forces air out of the pump cavity and OXYGEN SENSOR HEATER MONITOR into the vent system. When the solenoid is energized If there is an oxygen sensor (O2S) shorted to volt- and de energized, the cycle is repeated creating flow age DTC, as well as a O2S heater DTC, the O2S in typical diaphragm pump fashion. The pump is con- fault MUST be repaired first. Before checking the trolled in 2 modes: O2S fault, verify that the heater circuit is operating Pump Mode: The pump is cycled at a fixed rate to correctly. achieve a rapid pressure build in order to shorten the Effective control of exhaust emissions is achieved overall test length. by an oxygen feedback system. The most important Test Mode: The solenoid is energized with a fixed element of the feedback system is the O2S. The O2S duration pulse. Subsequent fixed pulses occur when is located in the exhaust path. Once it reaches oper- the diaphragm reaches the Switch closure point. ating temperature 300° to 350°C (572 ° to 662°F), the The spring in the pump is set so that the system sensor generates a voltage that is inversely propor- will achieve an equalized pressure of about 7.5” tional to the amount of oxygen in the exhaust. The water. The cycle rate of pump strokes is quite rapid information obtained by the sensor is used to calcu- as the system begins to pump up to this pressure. As late the fuel injector pulse width. This maintains a the pressure increases, the cycle rate starts to drop 14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio, off. If there is no leak in the system, the pump would the catalyst works best to remove hydrocarbons (HC), eventually stop pumping at the equalized pressure. If carbon monoxide (CO) and nitrogen oxide (NOx) from there is a leak, it will continue to pump at a rate rep- the exhaust. resentative of the flow characteristic of the size of the The voltage readings taken from the O2S sensor leak. From this information we can determine if the are very temperature sensitive. The readings are not leak is larger than the required detection limit (cur- accurate below 300°C. Heating of the O2S sensor is rently set at .040” orifice by CARB). If a leak is done to allow the engine controller to shift to closed revealed during the leak test portion of the test, the loop control as soon as possible. The heating element test is terminated at the end of the test mode and no used to heat the O2S sensor must be tested to ensure further system checks will be performed. that it is heating the sensor properly. After passing the leak detection phase of the test, The O2S sensor circuit is monitored for a drop in system pressure is maintained by turning on the voltage. The sensor output is used to test the heater LDP’s solenoid until the purge system is activated. by isolating the effect of the heater element on the Purge activation in effect creates a leak. The cycle O2S sensor output voltage from the other effects. rate is again interrogated and when it increases due 25 - 4 EMISSIONS CONTROL TJ EMISSIONS CONTROL (Continued) to the flow through the purge system, the leak check Normal vehicle miles or engine misfire can cause a portion of the diagnostic is complete. catalyst to decay. This can increase vehicle emissions The canister vent valve will unseal the system and deteriorate engine performance, driveability and after completion of the test sequence as the pump fuel economy. diaphragm assembly moves to the full travel position. The catalyst monitor uses dual oxygen sensors Evaporative system functionality will be verified by (O2S’s) to monitor the efficiency of the converter. The using the stricter evap purge flow monitor. At an dual O2S’s sensor strategy is based on the fact that appropriate warm idle the LDP will be energized to as a catalyst deteriorates, its oxygen storage capacity seal the canister vent. The purge flow will be clocked and its efficiency are both reduced. By monitoring up from some small value in an attempt to see a the oxygen storage capacity of a catalyst, its effi- shift in the 02 control system. If fuel vapor, indicated ciency can be indirectly calculated. The upstream by a shift in the 02 control, is present the test is O2S is used to detect the amount of oxygen in the passed. If not, it is assumed that the purge system is exhaust gas before the gas enters the catalytic con- not functioning in some respect. The LDP is again verter. The PCM calculates the A/F mixture from the turned off and the test is ended. output of the O2S. A low voltage indicates high oxygen content (lean mixture). A high voltage indicates a MISFIRE MONITOR low content of oxygen (rich mixture). Excessive engine misfire results in increased cata- When the upstream O2S detects a lean condition, lyst temperature and causes an increase in HC emis- there is an abundance of oxygen in the exhaust gas. sions. Severe misfires could cause catalyst damage. A functioning converter would store this oxygen so it To prevent catalytic convertor damage, the PCM can use it for the oxidation of HC and CO. As the monitors engine misfire. converter absorbs the oxygen, there will be a lack of The Powertrain Control Module (PCM) monitors oxygen downstream of the converter. The output of for misfire during most engine operating conditions the downstream O2S will indicate limited activity in (positive torque) by looking at changes in the crank- this condition. shaft speed. If a misfire occurs the speed of the As the converter loses the ability to store oxygen, crankshaft will vary more than normal. the condition can be detected from the behavior of the downstream O2S. When the efficiency drops, no FUEL SYSTEM MONITOR chemical reaction takes place. This means the con- To comply with clean air regulations, vehicles are centration of oxygen will be the same downstream as equipped with catalytic converters. These converters upstream. The output voltage of the downstream reduce the emission of hydrocarbons, oxides of nitro- O2S copies the voltage of the upstream sensor. The gen and carbon monoxide. The catalyst works best only difference is a time lag (seen by the PCM) when the Air Fuel (A/F) ratio is at or near the opti- between the switching of the O2S’s. mum of 14.7 to 1. To monitor the system, the number of lean-to-rich The PCM is programmed to maintain the optimum switches of upstream and downstream O2S’s is air/fuel ratio of 14.7 to 1. This is done by making counted. The ratio of downstream switches to short term corrections in the fuel injector pulse width upstream switches is used to determine whether the based on the O2S sensor output. The programmed catalyst is operating properly. An effective catalyst memory acts as a self calibration tool that the engine will have fewer downstream switches than it has controller uses to compensate for variations in engine upstream switches i.e., a ratio closer to zero. For a specifications, sensor tolerances and engine fatigue totally ineffective catalyst, this ratio will be one-to- over the life span of the engine. By monitoring the one, indicating that no oxidation occurs in the device. actual fuel-air ratio with the O2S sensor (short term) The system must be monitored so that when cata- and multiplying that with the program long-term lyst efficiency deteriorates and exhaust emissions (adaptive) memory and comparing that to the limit, increase to over the legal limit, the MIL will be illu- it can be determined whether it will pass an emis- minated. sions test. If a malfunction occurs such that the PCM cannot maintain the optimum A/F ratio, then the DESCRIPTION - TRIP DEFINITION MIL will be illuminated. The term “Trip” has different meanings depending on what the circumstances are. If the MIL (Malfunc- CATALYST MONITOR tion Indicator Lamp) is OFF, a Trip is defined as To comply with clean air regulations, vehicles are when the Oxygen Sensor Monitor and the Catalyst equipped with catalytic converters. These converters Monitor have been completed in the same drive cycle. reduce the emission of hydrocarbons, oxides of nitro- When any Emission DTC is set, the MIL on the gen and carbon monoxide. dash is turned ON. When the MIL is ON, it takes 3 TJ EMISSIONS CONTROL 25 - 5 EMISSIONS CONTROL (Continued) good trips to turn the MIL OFF. In this case, it an associated limp in will take two trips to illumi- depends on what type of DTC is set to know what a nate the MIL. “Trip” is. Refer to the Diagnostic Trouble Codes Description For the Fuel Monitor or Mis-Fire Monitor (contin- Charts in this section and the appropriate Power- uous monitor), the vehicle must be operated in the train Diagnostic Procedure Manual for diagnostic “Similar Condition Window” for a specified amount of procedures. time to be considered a Good Trip. If a Non-Contiuous OBDII Monitor fails twice in a DESCRIPTION - NON-MONITORED CIRCUITS row and turns ON the MIL, re-running that monitor The PCM does not monitor the following circuits, which previously failed, on the next start-up and systems and conditions that could have malfunctions passing the monitor, is considered to be a Good Trip. causing driveability problems. The PCM might not These will include the following: store diagnostic trouble codes for these conditions. • Oxygen Sensor However, problems with these systems may cause the • Catalyst Monitor PCM to store diagnostic trouble codes for other sys- • Purge Flow Monitor tems or components. For example, a fuel pressure • Leak Detection Pump Monitor (if equipped) problem will not register a fault directly, but could • EGR Monitor (if equipped) cause a rich/lean condition or misfire. This could • Oxygen Sensor Heater Monitor cause the PCM to store an oxygen sensor or misfire If any other Emission DTC is set (not an OBDII diagnostic trouble code Monitor), a Good Trip is considered to be when the Oxygen Sensor Monitor and Catalyst Monitor have FUEL PRESSURE been completed; or 2 Minutes of engine run time if The fuel pressure regulator controls fuel system the Oxygen Sensor Monitor or Catalyst Monitor have pressure. The PCM cannot detect a clogged fuel been stopped from running. pump inlet filter, clogged in-line fuel filter, or a It can take up to 2 Failures in a row to turn on the pinched fuel supply or return line. However, these MIL. After the MIL is ON, it takes 3 Good Trips to could result in a rich or lean condition causing the turn the MIL OFF. After the MIL is OFF, the PCM PCM to store an oxygen sensor or fuel system diag- will self-erase the DTC after 40 Warm-up cycles. A nostic trouble code. Warm-up cycle is counted when the ECT (Engine Coolant Temperature Sensor) has crossed 160°F and SECONDARY IGNITION CIRCUIT has risen by at least 40°F since the engine has been The PCM cannot detect an inoperative ignition coil, started. fouled or worn spark plugs, ignition cross firing, or open spark plug cables. DESCRIPTION - COMPONENT MONITORS There are several components that will affect vehi- CYLINDER COMPRESSION cle emissions if they malfunction. If one of these com- The PCM cannot detect uneven, low, or high engine ponents malfunctions the Malfunction Indicator cylinder compression. Lamp (MIL) will illuminate. Some of the component monitors are checking for EXHAUST SYSTEM proper operation of the part. Electrically operated The PCM cannot detect a plugged, restricted or components now have input (rationality) and output leaking exhaust system, although it may set a fuel (functionality) checks. Previously, a component like system fault. the Throttle Position sensor (TPS) was checked by the PCM for an open or shorted circuit. If one of FUEL INJECTOR MECHANICAL MALFUNCTIONS these conditions occurred, a DTC was set. Now there The PCM cannot determine if a fuel injector is is a check to ensure that the component is working. clogged, the needle is sticking or if the wrong injector This is done by watching for a TPS indication of a is installed. However, these could result in a rich or greater or lesser throttle opening than MAP and lean condition causing the PCM to store a diagnostic engine rpm indicate. In the case of the TPS, if engine trouble code for either misfire, an oxygen sensor, or vacuum is high and engine rpm is 1600 or greater the fuel system. and the TPS indicates a large throttle opening, a DTC will be set. The same applies to low vacuum if EXCESSIVE OIL CONSUMPTION the TPS indicates a small throttle opening. Although the PCM monitors engine exhaust oxygen All open/short circuit checks or any component that content when the system is in closed loop, it cannot has an associated limp in will set a fault after 1 trip determine excessive oil consumption. with the malfunction present. Components without 25 - 6 EMISSIONS CONTROL TJ EMISSIONS CONTROL (Continued)

THROTTLE BODY AIRFLOW PCM CONNECTOR ENGAGEMENT The PCM cannot detect a clogged or restricted air The PCM may not be able to determine spread or cleaner inlet or filter element. damaged connector pins. However, it might store diagnostic trouble codes as a result of spread connec- VACUUM ASSIST tor pins. The PCM cannot detect leaks or restrictions in the vacuum circuits of vacuum assisted engine control DESCRIPTION - HIGH AND LOW LIMITS system devices. However, these could cause the PCM The PCM compares input signal voltages from each to store a MAP sensor diagnostic trouble code and input device with established high and low limits for cause a high idle condition. the device. If the input voltage is not within limits and other criteria are met, the PCM stores a diagnos- PCM SYSTEM GROUND tic trouble code in memory. Other diagnostic trouble The PCM cannot determine a poor system ground. code criteria might include engine RPM limits or However, one or more diagnostic trouble codes may input voltages from other sensors or switches that be generated as a result of this condition. The mod- must be present before verifying a diagnostic trouble ule should be mounted to the body at all times, also code condition. during diagnostic.

DESCRIPTION - LOAD VALUE

ENGINE IDLE/NEUTRAL 2500 RPM/NEUTRAL All Engines 2% to 8% of Maximum Load 9% to 17% of Maximum Load

OPERATION - TASK MANAGER (pending) or the Task Manager has set a fault that The Task Manager determines which tests happen may cause a failure of the test (suspend). • when and which functions occur when. Many of the Pending diagnostic steps required by OBD II must be per- Under some situations the Task Manager will not formed under specific operating conditions. The Task run a monitor if the MIL is illuminated and a fault is Manager software organizes and prioritizes the diag- stored from another monitor. In these situations, the nostic procedures. The job of the Task Manager is to Task Manager postpones monitors pending resolu- determine if conditions are appropriate for tests to be tion of the original fault. The Task Manager does not run, monitor the parameters for a trip for each test, run the test until the problem is remedied. and record the results of the test. Following are the For example, when the MIL is illuminated for an responsibilities of the Task Manager software: Oxygen Sensor fault, the Task Manager does not run • Test Sequence the Catalyst Monitor until the Oxygen Sensor fault is • MIL Illumination remedied. Since the Catalyst Monitor is based on sig- • Diagnostic Trouble Codes (DTCs) nals from the Oxygen Sensor, running the test would • Trip Indicator produce inaccurate results. • • Freeze Frame Data Storage Conflict • Similar Conditions Window There are situations when the Task Manager does not run a test if another monitor is in progress. In Test Sequence these situations, the effects of another monitor run- In many instances, emissions systems must fail ning could result in an erroneous failure. If this con- diagnostic tests more than once before the PCM illu- flict is present, the monitor is not run until the minates the MIL. These tests are know as ’two trip conflicting condition passes. Most likely the monitor monitors.’ Other tests that turn the MIL lamp on will run later after the conflicting monitor has after a single failure are known as ’one trip moni- passed. tors.’ A trip is defined as ’start the vehicle and oper- For example, if the Fuel System Monitor is in ate it to meet the criteria necessary to run the given progress, the Task Manager does not run the EGR monitor.’ Monitor. Since both tests monitor changes in air/fuel Many of the diagnostic tests must be performed ratio and adaptive fuel compensation, the monitors under certain operating conditions. However, there will conflict with each other. • are times when tests cannot be run because another Suspend test is in progress (conflict), another test has failed Occasionally the Task Manager may not allow a two trip fault to mature. The Task Manager will sus- TJ EMISSIONS CONTROL 25 - 7 EMISSIONS CONTROL (Continued) pend the maturing of a fault if a condition exists DTC Self Erasure that may induce an erroneous failure. This prevents With one trip components or systems, the MIL is illuminating the MIL for the wrong fault and allows illuminated upon test failure and DTCs are stored. more precis diagnosis. Two trip monitors are components requiring failure For example, if the PCM is storing a one trip fault in two consecutive trips for MIL illumination. Upon for the Oxygen Sensor and the EGR monitor, the failure of the first test, the Task Manager enters a Task Manager may still run the EGR Monitor but maturing code. If the component fails the test for a will suspend the results until the Oxygen Sensor second time the code matures and a DTC is set. Monitor either passes or fails. At that point the Task After three good trips the MIL is extinguished and Manager can determine if the EGR system is actu- the Task Manager automatically switches the trip ally failing or if an Oxygen Sensor is failing. counter to a warm-up cycle counter. DTCs are automatically erased following 40 warm-up cycles if the MIL Illumination component does not fail again. The PCM Task Manager carries out the illumina- For misfire and fuel system monitors, the compo- tion of the MIL. The Task Manager triggers MIL illu- nent must pass the test under a Similar Conditions mination upon test failure, depending on monitor Window in order to record a good trip. A Similar Con- failure criteria. ditions Window is when engine RPM is within ±375 The Task Manager Screen shows both a Requested RPM and load is within ±10% of when the fault MIL state and an Actual MIL state. When the MIL is occurred. illuminated upon completion of a test for a third trip, the Requested MIL state changes to OFF. However, NOTE: It is important to understand that a compo- the MIL remains illuminated until the next key nent does not have to fail under a similar window of cycle. (On some vehicles, the MIL will actually turn operation to mature. It must pass the test under a OFF during the third key cycle) During the key cycle Similar Conditions Window when it failed to record for the third good trip, the Requested MIL state is a Good Trip for DTC erasure for misfire and fuel OFF, while the Actual MIL state is ON. After the system monitors. next key cycle, the MIL is not illuminated and both MIL states read OFF. DTCs can be erased anytime with a DRB III. Eras- ing the DTC with the DRB III erases all OBD II Diagnostic Trouble Codes (DTCs) information. The DRB III automatically displays a With OBD II, different DTC faults have different warning that erasing the DTC will also erase all priorities according to regulations. As a result, the OBD II monitor data. This includes all counter infor- priorities determine MIL illumination and DTC era- mation for warm-up cycles, trips and Freeze Frame. sure. DTCs are entered according to individual priority. DTCs with a higher priority overwrite lower Trip Indicator priority DTCs. The Trip is essential for running monitors and extinguishing the MIL. In OBD II terms, a trip is a Priorities set of vehicle operating conditions that must be met • Priority 0 —Non-emissions related trouble codes for a specific monitor to run. All trips begin with a • Priority 1 — One trip failure of a two trip fault key cycle. for non-fuel system and non-misfire. Good Trip • Priority 2 — One trip failure of a two trip fault The Good Trip counters are as follows: for fuel system (rich/lean) or misfire. • Specific Good Trip • Priority3—Twotrip failure for a non-fuel sys- • Fuel System Good Trip tem and non-misfire or matured one trip comprehen- • Misfire Good Trip sive component fault. • Alternate Good Trip (appears as a Global Good • Priority4—Twotrip failure or matured fault Trip on DRB III) for fuel system (rich/lean) and misfire or one trip cat- • Comprehensive Components alyst damaging misfire. • Major Monitor Non-emissions related failures have no priority. • Warm-Up Cycles One trip failures of two trip faults have low priority. Specific Good Trip Two trip failures or matured faults have higher pri- The term Good Trip has different meanings ority. One and two trip failures of fuel system and depending on the circumstances: misfire monitor take precedence over non-fuel system • If the MIL is OFF, a trip is defined as when the and non-misfire failures. Oxygen Sensor Monitor and the Catalyst Monitor have been completed in the same drive cycle. 25 - 8 EMISSIONS CONTROL TJ EMISSIONS CONTROL (Continued)

• If the MIL is ON and a DTC was set by the Fuel can determine under what vehicle operating condi- Monitor or Misfire Monitor (both continuous moni- tions the failure occurred. tors), the vehicle must be operated in the Similar The data stored in Freeze Frame is usually Condition Window for a specified amount of time. recorded when a system fails the first time for two • If the MIL is ON and a DTC was set by a Task trip faults. Freeze Frame data will only be overwrit- Manager commanded once-per-trip monitor (such as ten by a different fault with a higher priority. the Oxygen Sensor Monitor, Catalyst Monitor, Purge Flow Monitor, Leak Detection Pump Monitor, EGR CAUTION: Erasing DTCs, either with the DRB III or Monitor or Oxygen Sensor Heater Monitor), a good by disconnecting the battery, also clears all Freeze trip is when the monitor is passed on the next start- Frame data. up. • If the MIL is ON and any other emissions DTC was set (not an OBD II monitor), a good trip occurs Similar Conditions Window when the Oxygen Sensor Monitor and Catalyst Mon- The Similar Conditions Window displays informa- itor have been completed, or two minutes of engine tion about engine operation during a monitor. Abso- run time if the Oxygen Sensor Monitor and Catalyst lute MAP (engine load) and Engine RPM are stored Monitor have been stopped from running. in this window when a failure occurs. There are two Fuel System Good Trip different Similar conditions Windows: Fuel System To count a good trip (three required) and turn off and Misfire. the MIL, the following conditions must occur: FUEL SYSTEM • • Engine in closed loop Fuel System Similar Conditions Window — • Operating in Similar Conditions Window An indicator that ’Absolute MAP When Fuel Sys Fail’ • Short Term multiplied by Long Term less than and ’RPM When Fuel Sys Failed’ are all in the same threshold range when the failure occurred. Indicated by switch- • Less than threshold for a predetermined time ing from ’NO’ to ’YES’. • If all of the previous criteria are met, the PCM will Absolute MAP When Fuel Sys Fail — The count a good trip (three required) and turn off the stored MAP reading at the time of failure. Informs MIL. the user at what engine load the failure occurred. • Misfire Good Trip Absolute MAP — A live reading of engine load If the following conditions are met the PCM will to aid the user in accessing the Similar Conditions count one good trip (three required) in order to turn Window. • off the MIL: RPM When Fuel Sys Fail — The stored RPM • Operating in Similar Condition Window reading at the time of failure. Informs the user at • 1000 engine revolutions with no misfire what engine RPM the failure occurred. • Warm-Up Cycles Engine RPM — A live reading of engine RPM Once the MIL has been extinguished by the Good to aid the user in accessing the Similar Conditions Trip Counter, the PCM automatically switches to a Window. • Warm-Up Cycle Counter that can be viewed on the Adaptive Memory Factor — The PCM utilizes DRB III. Warm-Up Cycles are used to erase DTCs both Short Term Compensation and Long Term Adap- and Freeze Frames. Forty Warm-Up cycles must tive to calculate the Adaptive Memory Factor for occur in order for the PCM to self-erase a DTC and total fuel correction. • Freeze Frame. A Warm-Up Cycle is defined as fol- Upstream O2S Volts — A live reading of the lows: Oxygen Sensor to indicate its performance. For • Engine coolant temperature must start below example, stuck lean, stuck rich, etc. • and rise above 160° F SCW Time in Window (Similar Conditions • Engine coolant temperature must rise by 40° F Window Time in Window) — A timer used by the • No further faults occur PCM that indicates that, after all Similar Conditions have been met, if there has been enough good engine Freeze Frame Data Storage running time in the SCW without failure detected. Once a failure occurs, the Task Manager records This timer is used to increment a Good Trip. • several engine operating conditions and stores it in a Fuel System Good Trip Counter —ATrip Freeze Frame. The Freeze Frame is considered one Counter used to turn OFF the MIL for Fuel System frame of information taken by an on-board data DTCs. To increment a Fuel System Good Trip, the recorder. When a fault occurs, the PCM stores the engine must be in the Similar Conditions Window, input data from various sensors so that technicians Adaptive Memory Factor must be less than calibrated threshold and the Adaptive Memory Factor TJ EMISSIONS CONTROL 25 - 9 EMISSIONS CONTROL (Continued) must stay below that threshold for a calibrated • RPM When Misfire Occurred — The stored amount of time. RPM reading at the time of failure. Informs the user • Test Done This Trip — Indicates that the at what engine RPM the failure occurred. monitor has already been run and completed during • Engine RPM — A live reading of engine RPM the current trip. to aid the user in accessing the Similar Conditions MISFIRE Window. • Same Misfire Warm-Up State — Indicates if • Adaptive Memory Factor — The PCM utilizes the misfire occurred when the engine was warmed up both Short Term Compensation and Long Term Adap- (above 160° F). tive to calculate the Adaptive Memory Factor for • In Similar Misfire Window — An indicator total fuel correction. that ’Absolute MAP When Misfire Occurred’ and • 200 Rev Counter — Counts 0–100 720 degree ’RPM When Misfire Occurred’ are all in the same cycles. range when the failure occurred. Indicated by switch- • SCW Cat 200 Rev Counter — Counts when in ing from ’NO’ to ’YES’. similar conditions. • Absolute MAP When Misfire Occurred — • SCW FTP 1000 Rev Counter — Counts 0–4 The stored MAP reading at the time of failure. when in similar conditions. Informs the user at what engine load the failure • Misfire Good Trip Counter — Counts up to occurred. three to turn OFF the MIL. • Absolute MAP — A live reading of engine load • Misfire Data— Data collected during test. to aid the user in accessing the Similar Conditions • Test Done This Trip— Indicates YES when the Window. test is done.