Chrysler Caravan/Voyager/Town and Country 1996-1999

Exhaust Gas Recirculation System

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OPERATION



See Figures 1, 2, 3 and 4



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Fig. Fig. 1: EGR system assembly-2.4L engine



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Fig. Fig. 2: EGR system assembly-3.0L engine



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Fig. Fig. 3: EGR system assembly-3.3L and 3.8L engines



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Fig. Fig. 4: Typical components of the EGR valve, solenoid and transducer assembly

The Exhaust Gas Recirculation (EGR) system reduces oxides of Nitrogen (NOx) in the engine exhaust and helps prevent detonation (engine knock). Under normal operating conditions, engine cylinder temperature can reach over 3000°F (1649°C). The formation of NOx increases proportionally with combustion temperature. To reduce the emission of these oxides, 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 mixture lowers temperatures during combustion. The EGR system consists of the following components:



EGR tube
 
EGR valve
 
Electric EGR Transducer (EET)
 
Connecting hoses
 

The electric EGR transducer contains an electrically operated solenoid and a backpressure transducer. The Powertrain Control Module (PCM) operates the solenoid, determining when to energize the solenoid. Exhaust system backpressure controls the transducer.

When the PCM energizes the solenoid, vacuum doesn't reach the transducer. Vacuum flows to the transducer when the PCM de-energizes the solenoid. When exhaust system backpressure becomes high enough, it fully closes a bleed valve in the transducer. When the PCM de-energizes the solenoid and backpressure closes the transducer bleed valve, vacuum flows through the transducer to operate the EGR valve.

De-engergizing the solenoid, but not fully closing the transducer bleed hole (because of low backpressure), varies the strength of vacuum applied to the EGR valve. Varying the strength of the vacuum changes the amount of EGR supplied to the engine. This provides the correct amount of exhaust gas recirculation for different operating conditions. This system does not allow EGR at idle.

COMPONENT TESTING



EGR System On-Board Diagnostics

See Figure 4

The PCM performs an on-board diagnostic check of the EGR system. The diagnostic system uses the electric EGR transducer for the system tests.

The check activates only during certain conditions. When the conditions are met, the PCM energizes the transducer solenoid to disable the EGR system. The PCM checks for a change in the heated oxygen sensor signal. If the air/fuel ratio goes lean, the PCM will try to enrich the mixture. The PCM records a Diagnostic Trouble Code (DTC) if the EGR system is not operating properly. After registering a DTC, the PCM turns on the Check Engine lamp (malfunction indicator) after 2 consecutive trips. There are 2 types of failures sensed by the PCM; a short or open in the circuit, or a mechanical failure or loss of vacuum. The Malfunction Indicator Lamp (MIL) denotes the need for service.

If you find a problem indicated by the MIL and a DTC is set, first check for proper operation of the EGR system. If the system tests properly, check the system using Chrysler's DRB® or equivalent scan tool. Make sure to follow all of the instructions included with the scan tool.

EGR System Test

CAUTION
ALWAYS block the drive wheels and apply the parking brake anytime you are performing a test or adjustment in which the engine must be running.

1996 VEHICLES

See Figure 4

A failed or malfunctioning EGR system can cause engine spark knock, hesitation or sags, rough idle, stalling and/or increased emissions. To make sure the EGR system is operating properly, all passages and moving parts must be clean of deposits that could cause plugging or sticking. Make sure the hoses don't leak and replace any components that do leak.

Check the hose connections between the throttle body, intake manifold, EGR solenoid and transducer, and the EGR valve. Replace any hardened, cracked, melted or leaking hoses. Repair or replace faulty connectors.

  1. Check the EGR control system and EGR valve with the engine fully warmed up and running with the engine coolant temperature at 150°F or over. With the transmission in Neutral and the throttle closed, allow the engine to idle for about 70 seconds.
  2.  
  3. Abruptly accelerate the engine to about 2,000 rpm, but NOT over 3,000 rpm. The EGR valve stem should move when accelerating the engine.
  4.  
  5. Repeat the test a few times to confirm movement. If the valve stem moves, the EGR system is operating properly. If the stem doesn't move, then the EGR system is not operating properly.
  6.  
  7. Disconnect and plug the vacuum hose from the EGR valve.
  8.  

1997-99 VEHICLES

See Figure 4

  1. Check the condition of all EGR system hoses and tubes for leaks, blockage, cracks, kinks or hardening. Repair or replace them as necessary before beginning the test.
  2.  
  3. Make sure the hoses at both the EGR valve and EGR valve control are connected properly, and that the electrical connector is firmly attached at the valve control.
  4.  
  5. To check EGR system operation, connect a DRB® or equivalent scan tool to the 16-way data link connector. (The data link connector is located on the lower edge of the instrument panel, near the steering column.) Make sure to follow all of the manufacturer's instructions when connecting the scan tool and testing the EGR system.
  6.  
  7. After checking the system with the scan tool, proceed to the remaining EGR valve control tests.
  8.  

EGR Gas Flow Test

See Figure 4

Use this test to see if exhaust gas is flowing through the EGR system. It can also be used to determine if the EGR tube is plugged, or the system passages in the intake or exhaust manifolds are plugged.

The engine must be started, running and at normal operating temperature for this test. This test is not to be used as a complete test of the EGR system, but in conjunction with the other system tests.

  1. All engines are equipped with 2 fittings on the EGR valve. The upper fitting (located on the vacuum motor) supplies engine vacuum to a diaphragm within the EGR valve for valve operation. The lower fitting (located on the base of the EGR valve) is used to supply exhaust backpressure to the EGR valve control.
  2.  
  3. Disconnect the rubber hose from the vacuum motor fitting on top of the EGR valve vacuum motor.
  4.  
  5. Connect a hand-held vacuum pump to the vacuum motor fitting (top fitting).
  6.  
  7. Start the engine. Using the hand-held vacuum pump, slowly apply about 5 in. (17 kPa) of vacuum to the fitting on the EGR valve motor.
  8.  
  9. While applying a minimum 3 in. (10 kPa) of vacuum, and with the engine running at idle speed, the idle speed should drop or the engine may even stall, if the vacuum is applied quickly. This indicates that exhaust gas is flowing through the EGR tube between the intake and exhaust manifolds.
  10.  
  11. If the engine speed did not change, the EGR valve may be defective or the EGR tube may be plugged with carbon, or the passages in the intake and/or exhaust manifold may be plugged with carbon. Perform the following to see if the components are plugged:
    1. Remove the EGR valve from the engine, as outlined later in this section.
    2.  
    3. Apply vacuum to the vacuum motor fitting and check the stem on the valve. If it's moving, the EGR valve is working properly and the problem is either a plugged EGR tube or plugged passages at the intake or exhaust manifolds (refer to the next step).
    4.  
    5. Remove the EGR tube between the intake and exhaust manifolds. Check and clean the EGR tube and its related openings on the manifolds.
    6.  

  12.  
  13. Do not try to clean the EGR valve. If the valve shows evidence of heavy carbon build-up near the base, replace it.
  14.  

EGR Valve Leakage Test

See Figure 4

If the engine will not idle, stalls while idling or the idle is rough or slow, the poppet valve, located at the base of the EGR valve, may be leaking in the closed position.

  1. The engine should be OFF for the following test.
  2.  
  3. Disconnect the rubber hose from the fitting at the top (vacuum motor) side of the EGR valve, and perform the following:
    1. Connect a hand-held vacuum pump to this fitting.
    2.  
    3. Apply 15 in. (51 kPa) of vacuum to the pump, then observe the gauge reading on the pump.
    4.  
    5. If the vacuum falls off, the diaphragm in the EGR valve has ruptured.
    6.  
    7. Replace the EGR valve, as outlined later in this section.The EGR valve, valve control and attaching hoses are replaced as an assembly.
    8.  
    9. Go on to the next step.
    10.  

  4.  
  5. A small metal fitting (backpressure fitting) is located at the base of the EGR valve. A rubber
  6.  

backpressure hose connects it to the backpressure fitting on the EGR valve control. Disconnect this hose from the EGR valve fitting.

  1. Remove the air cleaner inlet tube from the throttle body.
  2.  
  3. Using compressed air from an air nozzle with a rubber tip, apply about 50 psi (345 kPa) of regulated air to the metal backpressure fitting on the EGR valve.
  4.  
  5. By hand, open the throttle to the wide open position. Air should NOT be heard coming from the intake manifold while applying air pressure to the fitting.
  6.  
  7. If air CAN be heard coming from the intake manifold, the poppet valve is leaking at the bottom of the EGR valve. Replace the EGR valve.
  8.  

EGR Valve Control (Transducer) Test

See Figure 4

The following procedures apply to testing the vacuum transducer portion of the valve. The electrical operation of the valve must be checked using the Chrysler DRB, or equivalent, scan tool. Be sure to follow the instructions that accompany the scan tool.

  1. Disconnect the rubber back-pressure hose from the fitting at the bottom of the EGR valve.
  2.  
  3. Connect a hand-held vacuum pump to this fitting and apply 10 inches of vacuum. If the vacuum falls off, the valve diaphragm is leaking.
  4.  
  5. Replace the EGR valve assembly and continue with further testing.
  6.  
  7. Disconnect the rubber hose at the EGR valve vacuum inlet fitting and connect a vacuum gauge to this hose.
  8.  
  9. Start the engine and allow it to run until it has reached operating temperature. Hold the engine speed at approximately 1500 rpm while checking for steady engine vacuum (full manifold) at this hose.
  10.  
  11. If engine vacuum is not present, check the vacuum line to the engine and repair as necessary before continuing.
  12.  
  13. Reconnect the hose to the EGR valve vacuum inlet fitting, then disconnect the hose from the outlet fitting. Connect a vacuum gauge to this fitting.
  14.  
  15. Disengage the wiring harness connector from the valve control, which will then simulate an open circuit (no ground from the PCM) at the valve.
  16.  
  17. Start the engine and allow it to reach operating temperature. Hold the engine speed to approximately 2000 rpm while checking for steady engine vacuum (full manifold) at this fitting.
  18.  

To allow full manifold vacuum to flow through the valve, exhaust back-pressure must be present at the valve. It must be high enough to hold the bleed valve in the transducer portion of the valve closed.

  1. With the aid of an assistant, momentarily (1-2 seconds) hold a rag over the tailpipe opening to build up exhaust back-pressure while observing the vacuum gauge reading. Be sure to wear heavy gloves while doing this.
  2.  

Do not cover the tailpipe opening for an extended period of time or damage to components or overheating could result.

  1. As temporary back-pressure is built, full manifold vacuum should be observed at the vacuum outlet fitting. Without back-pressure, and the engine at approximately 2000 rpm, the gauge reading will be low. This low reading is normal. At idle speed, the gauge reading will be erratic. This is also normal.
  2.  
  3. If full manifold vacuum is not present at the outlet fitting, but is present at the inlet fitting, replace the valve.
  4.  

REMOVAL & INSTALLATION



EGR Valve and Electric EGR Transducer

See Figures 1, 2, 3 and 5



Click image to see an enlarged view

Fig. Fig. 5: Unplug the electrical connector from the transducer, then the vacuum hose

The EGR valve and Electric EGR Transducer (EET) are serviced as an assembly.

  1. Disconnect the negative battery cable.
  2.  
  3. Unplug the electrical connector from the EET.
  4.  
  5. Detach the vacuum hose from the EET.
  6.  
  7. Remove the EGR valve mounting bolts, then remove the EGR valve and EET.
  8.  
  9. Remove and discard the old gaskets. Thoroughly clean the gasket mating surfaces and/or passages.
  10.  
  11. Check for any signs of leakage or cracked surfaces. Repair or replace as necessary.
  12.  

To install:
  1. Using new gaskets, loosely install the EGR valve onto the intake manifold. Tighten the mounting bolts to 16 ft. lbs. (22 Nm).
  2.  
  3. Install the EET onto the mounting bracket.
  4.  
  5. Attach the electrical and vacuum hose connections to the EET.
  6.  
  7. Connect the negative battery cable.
  8.  

EGR Tube

See Figures 1, 6 and 7



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Fig. Fig. 6: EGR tube removal-3.0L engine



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Fig. Fig. 7: EGR tube removal-3.3L and 3.8L engines

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the exhaust manifold-to-EGR tube flange fasteners. Be careful not to lose the gasket.
  4.  
  5. If necessary, remove the EGR valve nuts at the intake manifold. Be careful not to lose the gasket.
  6.  
  7. Remove the intake manifold-to-EGR tube flange fasteners. Be careful not to lose the gasket.
  8.  
  9. Remove the EGR tube.
  10.  
  11. Discard the old gaskets. Thoroughly clean the gasket mating surfaces and/or passages.
  12.  
  13. Check for any signs of leakage or cracked surfaces. Repair or replace as necessary.
  14.  

To install:
  1. Loosely install the EGR tube and fasteners, along with new gaskets, onto the intake and exhaust manifolds.
  2.  
  3. Tighten the EGR tube mounting fasteners to 16 ft. lbs. (22 Nm).
  4.  
  5. Connect the negative battery cable.
  6.  

 
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