Emissions Control: Overview Jeep Compass I рестайлинг

DEFINITION AND MONITOR OPERATION

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

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

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

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

INPUT SIGNAL OPERATION

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

Scheme 2

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 warmup 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 SYSTEMS .

Note. Various diagnostic procedures may actually cause a diagnostic monitor to set a DTC. For instance, pulling a spark plug wire to perform a spark test may set the misfire code. When a repair is completed and verified, use the scan tool to erase all 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. (Scheme 2)

DESCRIPTION

The canister mounts to a left rear rail in the rear of the vehicle. The vacuum and vapor tube connect to the top of the canister.

OPERATION

All vehicles use a maintenance free, evaporative (EVAP) canister. Fuel tank vapors vent into the canister. The canister temporarily holds the fuel vapors until intake manifold vacuum draws them into the combustion chamber. The Powertrain Control Module (PCM) purges the canister through the proportional purge solenoid. The PCM purges the canister at predetermined intervals and engine conditions.

The plastic fuel fill cap is threaded/quarter turn onto the end of the fuel filler tube. It's purpose is to retain vapors and fuel in the fuel tank.

The loss of any fuel vapor out of fuel filler tube is prevented by the use of 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.

Scheme 3

The fuel tank pressure sensor provides the PCM with information on vapor pressure inside the fuel tank. The sensor is a diaphragm-type pressure sensor and varies its voltage output depending on fuel tank pressure. When the fuel tank isolation valve is activated (closed), preventing fuel vapors from leaving the tank, the PCM will monitor the fuel tank pressure sensor to prevent pressure from increasing or decreasing to an unsafe level.

Excessive fuel tank pressure could cause fuel vapors to vent out the fuel filler cap or damage system components while insufficient fuel tank pressure (vacuum) caused by lack of air entering the tank to take the place of consumed fuel could lead to collapsed tank, lines or loss of fuel pressure.

Scheme 4

Note. The Fuel Tank Pressure sensor is located under the rear of the vehicle, and is integrated in the vent tube coming from the fuel pump module.

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1. Disconnect and isolate the negative battery cable.
2. Remove the fuel filler cap to relieve tank pressure.
3. Raise and support the vehicle. Refer to «Hoisting, Standard Procedure»(ref-462458-S12121678172012040500000) .
4. Disconnect the fuel tank pressure sensor electrical connector (1).
5. Carefully raise the retaining tab (2), rotate and remove the fuel tank pressure sensor (1) from the fuel tank vent tube.
6. The fuel tank pressure sensor seal (1) can be reused if not damaged.

Scheme 7

1. The fuel tank pressure sensor seal (1) can be reused if not damaged.
2. Install the fuel tank pressure sensor (1) into the fuel tank vent tube and rotate into position.
3. Connect the fuel tank pressure sensor electrical connector (1).
4. Lower the vehicle.
5. Install the fuel filler cap.
6. Connect the negative battery cable and tighten nut to 5 N.m (45 in. lbs.).

The vehicle uses a Linear Purge Valve. The linear purge valve is a solenoid that regulates the rate of vapor flow from the EVAP canister to the intake manifold. The PCM operates the linear purge valve.

All vehicles use a linear purge valve. The linear purge valve is a solenoid that regulates the rate of vapor flow from the evaporative emission (EVAP) canister to the intake manifold. The powertrain control module (PCM) operates the linear purge valve.

During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged.

The linear purge valve operates at a frequency of 200 hz and is controlled by an engine controller circuit that senses the current being applied to the linear purge valve and then adjusts that current to achieve the desired purge flow. The linear purge valve controls the purge rate of fuel vapors from the vapor canister and fuel tank to the engine intake manifold.

Scheme 8

1. Disconnect and isolate negative battery cable at battery.
2. Disconnect electrical connector (4) from evaporator purge solenoid (1).
3. Remove purge hose (3) from evaporator purge solenoid (1).
4. Remove quick connect fuel tank hose (2) from evaporator purge solenoid (1).
5. Release tab to remove evaporator purge solenoid (1) from body bracket (5).

The EGR system reduces oxides of nitrogen (NOx) in the engine exhaust. This is accomplished by allowing a predetermined amount of hot exhaust gas to recirculate and dilute the incoming fuel/air mixture.

A malfunctioning EGR system can cause engine stumble, sags, or hesitation, rough idle, engine stalling and poor driveability.

An EGR valve assembly is located toward the front of the engine. An EGR solenoid, located on top of the intake manifold near EGR valve. The EGR solenoid controls the "on time" of the EGR valve. The Powertrain Control Module (PCM) operates the EGR solenoid. The vacuum pump supplies vacuum for the EGR solenoid and the EGR valve. This pump also supplies vacuum for operation of the power brake booster and the heating and air conditioning system. The pump is located in the rear of the cylinder head and is driven by the exhaust camshaft. When the PCM supplies a variable ground signal to the EGR solenoid, EGR system operation begins. The PCM will monitor and determine when to supply and remove this variable ground signal. This will depend on inputs from the engine coolant temperature, throttle position and engine speed sensors. When the variable ground signal is supplied to the EGR solenoid, vacuum will be allowed to pass through the EGR solenoid and on to the EGR valve through a connecting hose.

Exhaust gas recirculation will begin in this order when

1. The PCM determines that EGR system operation is necessary.
2. The engine is running to operate the vacuum pump.
3. A variable ground signal is supplied to the EGR solenoid.
4. Variable vacuum passes through the EGR solenoid to the EGR valve.
5. The inlet seat (poppet valve) at the bottom of the EGR valve opens to dilute and recirculate exhaust gas back into the mixing chamber.

The EGR system will be shut down by the PCM after 60 seconds of continuous engine idling to improve idle quality.

The EGR valve is mounted inline to the EGR cooler.

The engines use Exhaust Gas Recirculation (EGR) systems. The EGR system reduces oxides of nitrogen (NOx) in engine exhaust and helps prevent detonation (engine knock). Under normal operating conditions, engine cylinder temperature can reach more than 1649°C (3000°F). Formation of NOx increases proportionally with combustion temperature. To reduce the emission of these oxides, the cylinder temperature must be lowered. The system allows a predetermined amount of hot exhaust gas to recirculate and dilute the incoming air/fuel mixture. The diluted air/fuel mixture reduces peak flame temperature during combustion.

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1. Disconnect the negative battery cable.
2. Remove engine cover.
3. Disconnect the EGR back pressure transducer harness connector (1).
4. Disconnect the vacuum line (1) from the EGR control valve actuator.
5. Disconnect the vacuum supply line (1) to the EGR solenoid.
6. Remove EGR tube bolts (1) and the EGR tube (2).
7. Disconnect coolant hoses (1) from the EGR cooler (2).
8. Remove the bolt (1) securing the oil dip stick tube.
9. Remove the bolt (1) securing the vacuum tube.
10. Remove bolts (1) and the heat shield (2).
11. Disconnect the wire harness retainers (1).
12. Remove bolts (1) and the EGR support bracket (2).
13. Disconnect the EGR valve harness connector (1).
14. Remove the upper EGR cooler bolt (1) and bracket (2).
15. Remove the lower EGR cooler bolt (1).
16. Remove the support bracket bolt (1).
17. Remove two bolts (1) and the EGR cooler manifold.
18. Remove bolts (1) and the EGR valve (2).

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Scheme 25

1. Clean all the gasket surface areas.
2. Install a new gasket (2) onto the EGR cooler (1).
3. Install a new gasket (2) onto the EGR inlet pipe (1).
4. Install EGR valve (2). Tighten bolts (1) to 9 N.m (80 in. lbs.).
5. Clean the gasket surfaces and install a new EGR manifold gasket (1).
6. Install the EGR manifold. Tighten bolts (1) to 9 N.m (80 in. lbs.).
7. Install the support bracket bolt (1). Tighten bolt (1) to 9 N.m (80 in. lbs.).
8. Install the lower EGR cooler support bolt (1). Tighten bolt (1) to 9 N.m (80 in. lbs.).
9. Install the upper EGR cooler support bolt (1). Tighten bolt (1) to 9 N.m (80 in. lbs.).
10. Disconnect the EGR valve harness connector (1).
11. Install the EGR support bracket (2). Tighten bolts (1) to 9 N.m (80 in. lbs.).
12. Connect the wire harness retainers (1).
13. Install the heat shield (2). Tighten bolts (1) to 9 N.m (80 in. lbs.).
14. Install the bolt (1) securing the vacuum tube and tighten to 9 N.m (80 in. lbs.).
15. Install the bolt (1) securing the oil dip stick tube and tighten bolt (1) to 9 N.m (80 in. lbs.).
16. Connect coolant hoses (1) from the EGR cooler (2).
17. Install the EGR tube (2). Tighten bolts (1) to 9 N.m (80 in. lbs.).
18. Connect the vacuum supply line (1) to the EGR solenoid.
19. Connect EGR valve vacuum line (1).
20. Connect the EGR back pressure transducer harness connector (1).
21. Install engine cover.
22. Connect the negative battery cable.

Scheme 26

1. Disconnect negative battery cable.
2. Remove the engine cover.
3. Remove the mixing chamber. Refer to «MANIFOLD, Intake, Removal»(ref-462490-S15372992492012040500000) or «MANIFOLD, Intake, Removal»(ref-462491-S18236158312012040500000) or «MANIFOLD, Intake, Removal»(ref-462492-S08135950942012040500000) .
4. Remove bolts (2) and the EGR air flow control valve (3).

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1. Clean all gasket matting surfaces.
2. Install new gasket (1) on the lower mixing chamber (2).
3. Install new gasket (1) onto inlet housing (2).
4. Install the EGR air flow control valve (3) to mixing chamber. Tighten bolts (2) to 9 N.m (80 in. lbs.).
5. Install the mixing chamber Refer to «MANIFOLD, Intake, Installation»(ref-462490-S27881009032012040500000) or «MANIFOLD, Intake, Installation»(ref-462491-S09476845472012040500000) or «MANIFOLD, Intake, Installation»(ref-462492-S31851870472012040500000) .
6. Install the engine cover.
7. Connect negative battery cable.

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1. Disconnect the negative battery cable.
2. Remove the engine cover.
3. Partially drain the cooling system. Refer to «Standard Procedure»(ref-462462-S03285651472012040500000) .
4. Disconnect the vacuum line (1) from the EGR control valve actuator.
5. Disconnect the EGR cooler bypass coolant hose (1).
6. Remove bolts (2) and position aside EGR cooler bypass vacuum diaphragm (3).
7. Remove bolts (1) and the EGR cooler bypass valve (2).

Scheme 31

1. Clean the gasket mating surfaces.
2. Install new O-ring gaskets (1 and 2).
3. Install the EGR bypass valve (2). Tighten bolts (1) to 9 N.m (80 in. lbs.).
4. Position the EGR cooler bypass vacuum diaphragm (3). Tighten bolts (2) to 12 N.m (106 in. lbs.).
5. Connect the EGR cooler bypass coolant hose (1).
6. Connect the vacuum line (1) to the EGR control valve actuator.
7. Fill the cooling system. Refer to «Standard Procedure»(ref-462462-S03285651472012040500000) .
8. Install the engine cover.
9. Connect the negative battery cable.
10. Start the engine and check for leaks.

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

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

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