Emissions Control System: Other Dodge Nitro I

DUTY CYCLE EVAP CANISTER PURGE SOLENOID

1. Connect quick-connect fittings (3) and (4) to solenoid.
2. Connect electrical connector (5).
3. Push solenoid assembly (1) onto the tongue-type bracket (2).
4. The vapor/vacuum lines and hoses must be firmly connected. Also check the vapor/vacuum lines at the ESIM switch and filter for damage or leaks. If a leak is present, a Diagnostic Trouble Code (DTC) may be set.

FUEL TANK FILLER TUBE CAP

The plastic fuel tank filler tube cap is threaded onto the end of the fuel fill tube. All models are equipped with a 1/4 turn cap.

The loss of any fuel or vapor out of fuel filler tube is prevented by the use of a pressure-vacuum fuel fill cap. Relief valves inside the cap will release fuel tank pressure at predetermined pressures. Fuel tank vacuum will also be released at predetermined values. This cap must be replaced by a similar unit if replacement is necessary. This is in order for the system to remain effective.

ORVR

The ORVR (On-Board Refueling Vapor Recovery) system consists of a unique fuel tank, flow management valve, fluid control valve, one-way check valve and vapor canister.

The ORVR (On-Board Refueling Vapor Recovery) system is used to remove excess fuel tank vapors. This is done while the vehicle is being refueled.

Fuel flowing into the fuel filler tube (approx. 1" I.D.) creates an aspiration effect drawing air into the fuel fill tube. During refueling, the fuel tank is vented to the EVAP canister to capture escaping vapors. With air flowing into the filler tube, there are no fuel vapors escaping to the atmosphere. Once the refueling vapors are captured by the EVAP canister, 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 purge solenoid so that there is no, or minimal impact on driveability or tailpipe emissions.

As fuel starts to flow through the fuel fill tube, it opens the normally closed check valve and enters the fuel tank. Vapor or air is expelled from the tank through the control valve and on to the vapor canister. Vapor is absorbed in the EVAP canister until vapor flow in the lines stops. This stoppage occurs following fuel shut-off, or by having the fuel level in the tank rise high enough to close the control valve. This control valve contains a float that rises to seal the large diameter vent path to the EVAP canister. At this point in the refueling process, fuel tank pressure increases, the check valve closes (preventing liquid fuel from spiting back at the operator), and fuel then rises up the fuel filler tube to shut off the dispensing nozzle.

Scheme 20

A PCV valve (1) using a rubber sealing O-ring (2) is used.

Scheme 21

The PCV valve is threaded into a metal fitting. The valve (2) is located at the rear of the left cylinder head.

Scheme 22

A typical enclosed crankcase ventilation system is shown in illustration .

The PCV system operates by engine intake manifold vacuum. Filtered air is routed into the crankcase through the air cleaner hose. The metered air, along with crankcase vapors, are drawn through the PCV valve (4) and into a passage in the intake manifold. The PCV system manages crankcase pressure and meters blow by gases to the intake system, reducing engine sludge formation.

The PCV valve contains a spring loaded plunger. This plunger meters the amount of crankcase vapors routed into the combustion chamber based on intake manifold vacuum.

Scheme 23

When the engine is not operating or during an engine pop-back, the spring forces the plunger back against the seat. This will prevent vapors from flowing through the valve.

Scheme 24

During periods of high manifold vacuum, such as idle or cruising speeds, vacuum is sufficient to completely compress spring. It will then pull the plunger to the top of the valve. In this position there is minimal vapor flow through the valve.

Scheme 25

During periods of moderate manifold vacuum, the plunger is only pulled part way back from inlet. This results in maximum vapor flow through the valve.

VACUUM LINES

A vacuum schematic for emission related items can be found on the VECI label. Refer to Vehicle Emission Control Information (VECI) Label for schematic location.

Scheme 26

The ESIM (Evaporative System Integrity Monitor) 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 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 adapter to maintain a vertical position. When the ESIM is installed vertically, the electrical connector is in the 3 o'clock position.

Scheme 27

The ESIM assembly consists of a housing, a small weight and a large weight that serve as check valves, a diaphragm, a switch and a cover. There is one large weight and one small weight check valve 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.

Scheme 28

The ESIM (Evaporative System Integrity Monitor), while physically different than the NVLD system, performs the same basic function as the NVLD does - controlling evaporative emissions. The ESIM has been simplified because the solenoid used on the NVLD is not used on the ESIM.

The ESIM consists of housing, two check valves (sometimes referred to as weights), a diaphragm, a switch and a cover. The larger check valve seals for pressure and the smaller one seals for vacuum.

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 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 evap. system during engine off conditions. If the evap. 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 gas cap is loose or missing. 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

EVAP CANISTER

A maintenance free, EVAP canister is used on all vehicles. The EVAP canister is filled with granules of an activated carbon mixture. Fuel vapors entering the EVAP canister are absorbed by the charcoal granules.

Fuel tank pressure vents into the EVAP canister. Fuel vapors are temporarily held in the canister until they can be drawn into the intake manifold. The duty cycle EVAP canister purge solenoid allows the EVAP canister to be purged at predetermined times and at certain engine operating conditions.

The EVAP canister is also to be considered as part of the ORVR system.

Scheme 29

The EVAP canister (1) is located under the vehicle behind the plastic splash shield (4) used for the left/rear tire. The ESIM switch (2) is attached to the EVAP canister.

Scheme 30

Scheme 31

1. Raise and support vehicle.
2. Clean dirt or debris from canister vacuum lines.
3. Disconnect electrical connector (3) at ESIM switch (2).
4. Disconnect rubber hose (6) from ESIM switch (2).
5. Disconnect quick-connect fitting (5) at EVAP canister.
6. Remove nut/bolt (1) at front of canister mounting bracket (2).
7. To remove canister, pull straight forward until pins (1) have cleared bracket (2).

VALVE - EGR - 3.7L

1. Clean gasket area (1) at rear of left cylinder head where it joins base of EGR valve.
2. Clean EGR tube where it joins EGR valve.
3. Position new gasket between EGR valve and cylinder head.
4. Position EGR valve to cylinder head. Install and tighten two bolts (2). Tighten to 9 N.m (80 in. lbs.).
5. Position new gasket (3) between EGR tube flange and EGR valve assembly.
6. Position EGR tube (1) to side of EGR valve. Position end of tube (6) into intake manifold. Install two bolts (2). Tighten to 11 N.m (97 in. lbs.).
7. Connect electrical connector (3) to top of EGR valve solenoid (1).
8. Connect negative battery cable.
9. Using a diagnostic scan tool, erase any previously recorded DTC's (Diagnostic Trouble Codes).

Scheme 32

The electronic EGR valve and solenoid assembly (1) is attached to the rear of the right cylinder head (2).

Scheme 33

1. Use a diagnostic scan tool to record any DTC's (Diagnostic Trouble Codes).
2. Disconnect and isolate the negative battery cable. An exhaust gas routing tube (5) connects the EGR valve (1) to the intake manifold.
3. Remove two flange mounting bolts (3) at intake manifold.
4. Remove two flange bolts (3) at solenoid (2).
5. Separate tube (4) from solenoid (2). Slip opposite end of tube (4) from intake manifold.
6. Remove and discard gasket (5) located between EGR valve solenoid and tube flange.
7. Disconnect electrical connector (6) at solenoid (1).
8. Remove two EGR solenoid/valve mounting bolts (6).
9. Remove solenoid/valve assembly (2) from rear of cylinder head.
10. Remove and discard gasket located between EGR solenoid/valve and cylinder head.

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) (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)

EGR Monitor

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.

Mis-Fire Monitor

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 Mis-Fire 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.