Jeep XJ. Manual — part 529
Generic Scan Tool Code
DRB III
T
Scan Tool Display
P1520
Vehicle Speed Gov Analog Ctrl Control Contact Alone
P1600
Battery Voltage SRC High Exceeded
P1605
Terminal #15 Plausibility After Startup
P1610
Regulator Lower Regulator Limit
Regulator Upper Regulator Limit
P1615
Microcontroller Gate-Array Monitoring
Microcontroller Gate-Array Watchdog
Microcontroller Prepare Fuel Quantity Stop
Microcontroller Recovery Was Occurred
Microcontrller Redundant Overrun Monitoring
P1620
U_REF (2.5V)
P1630
Solenoid Valve Controller Open Circuit
Solenoid Valve Controller Short Circuit
P1635
Glow Relay Controller Open Circuit
Glow Relay Controller Short Circuit
P1660
Redundant Emer. Stop Plausibility In After-Run
Redundant Emer. Stop Powerstage Defective
P1680
EEPROM Plausibility Checksum Error for Adj.
EEPROM Plausibility Checksum Error in CC212
EEPROM Plausibility Communication With EEPROM
EEPROM Plausibility Func. Switch Wrong or Missing
EEPROM Plausibility VIN Checksum Error
P1685
Vehicle Theft Alarm Immobilizer Signal Lost
Vehicle Theft Alarm Invalid SKIM Message
P1690
Fan Control Open Circuit
Fan Control Short Circuit
P1695
AC Control Short Circuit
AC Control OpenCircuit
P1703
Brake Signal Plaus With Redundant Contact
P1725
Inductive Aux. Speed Sensor Dynamic Plausibilty
Inductive Aux. Speed Sensor Overspeed Recognition
Inductive Aux Speed Sensor Plausibilty
Inductive Aux. Speed Sensor Static Plausibilty
25 - 4
EMISSION CONTROL SYSTEM
XJ
DESCRIPTION AND OPERATION (Continued)
2000 JEEP CHEROKEE
PCM DRBIII
T CODES
Generic Scan Tool Code
DRBIII Scan Tool Display
P0117
Engine Coolant Volts Low
P0118
Engine Coolant Volts High
P0462
Fuel Level Sending Unit volts Too Low
P0463
Fuel Level Sending Unit volts Too High
P0500
Vehicle Speed Signal
P0522
Oil Pressure Sense Low
P0523
Oil Pressure Sense High
P0601
Internal Controller Failure
P0622
Generator Field Not Switching Properly
P1296
5 VDC Output
P1391
Loss of Cam or Crank
P1492
Ambient/Batt temp Sen Volts Too High
P1493
Ambient/Batt temp Sen Volts Too Low
P1594
Charging System Voltage Too High
P1682
Charge Output Low
P1685
SKIM Invalid Key
P1686
No SKIM Bus Message Recieved
P1687
No MIC Bus Message
P1696
PCM Failure EEPROM Write Denied
XJ
EMISSION CONTROL SYSTEM
25 - 5
DESCRIPTION AND OPERATION (Continued)
2000 JEEP CHEROKEE
EXHAUST EMISSION CONTROLS—2.5L DIESEL ENGINE
TABLE OF CONTENTS
page
page
DESCRIPTION AND OPERATION
EXHAUST GAS RECIRCULATION (EGR)
SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
DIAGNOSIS AND TESTING
. . . . . . . . . . . . . . . . . . . . 7
. . . . . . . . . . . . . . . . . . . . 7
REMOVAL AND INSTALLATION
EGR VALVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
EGR TUBE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
ELECTRIC VACUUM MODULATOR (EVM) . . . . . . . 8
SPECIFICATIONS
TORQUE CHART—2.5L DIESEL . . . . . . . . . . . . . . 8
DESCRIPTION AND OPERATION
VACUUM HOSE ROUTING SCHEMATIC
DESCRIPTION
Vacuum for the EGR system is supplied by the
internal engine mounted vacuum pump. Refer to
EGR System Operation for vacuum pump informa-
tion. Vacuum harness routing for emission related
components is displayed in (Fig. 1).
EXHAUST GAS RECIRCULATION (EGR)
SYSTEM
DESCRIPTION
The EGR system reduces oxides of nitrogen (NOx)
in the engine exhaust. This is accomplished by allow-
ing 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 stall-
ing and poor driveability.
OPERATION
The system consists of:
• An EGR valve assembly. The valve is located on
the side of the intake manifold.
• An Electric Vacuum Modulator (EVM). The EVM
is sometimes referred to as the EGR control solenoid
or EGR duty cycle solenoid. The EVM controls the
“on time” of the EGR valve.
• The ECM operates the EVM. The ECM is
located inside the vehicle under the instrument
panel.
• An EGR tube connects a passage in the EGR
valve to the rear of the exhaust manifold.
• The vacuum pump supplies vacuum for the
EVM and the EGR valve. This pump also supplies
vacuum for operation of the power brake boosterb
and the heating and air conditioning system. The
pump is located internally in the front of the engine
block (Fig. 2) and is driven by the crankshaft gear.
• Vacuum lines and hoses connect the various
components.
When the ECM supplies a variable ground signal
to the EVM, EGR system operation starts to occur.
The ECM will monitor and determine when to supply
and remove this variable ground signal. This will
depend on inputs from the engine coolant tempera-
ture, throttle position and engine speed sensors.
Fig. 1 Typical Hose Routing
1 – EGR VALVE
2 – TO VACUUM PUMP
3 – ELECTRIC VACUUM MODULATOR (EVM)
25 - 6
EMISSION CONTROL SYSTEM
XJ
2000 JEEP CHEROKEE
When the variable ground signal is supplied to the
EVM, vacuum from the vacuum pump will be
allowed to pass through the EVM and on to the EGR
valve with a connecting hose.
Exhaust gas recirculation will begin in this order
when:
• The ECM determines that EGR system opera-
tion is necessary.
• The engine is running to operate the vacuum
pump.
• A variable ground signal is supplied to the EVM.
• Variable vacuum passes through the EVM to the
EGR valve.
• The inlet seat (poppet valve) at the bottom of
the EGR valve opens to dilute and recirculate
exhaust gas back into the intake manifold.
The EGR system will be shut down by the ECM
after 60 seconds of continuous engine idling to
improve idle quality.
DIAGNOSIS AND TESTING
EGR GAS FLOW TEST
Refer to the 2000 XJ Diesel Powertrain Diagnostic
Manual for complete test procedure.
EGR SOLENOID TEST
VACUUM TEST
With the engine running, disconnect the vacuum
supply line at the fitting on the Electric Vacuum
Modulator (EVM). Vacuum should be no less than 20
inches. If vacuum is lower, check for leaks in vacuum
supply line. If leaks cannot be found, check for low
vacuum at vacuum pump.
REMOVAL AND INSTALLATION
EGR VALVE
REMOVAL
(1) Disconnect vacuum line at EGR valve vacuum
supply fitting.
(2) Loosen the tube fitting at exhaust manifold end
of EGR tube.
(3) Remove the two bolts retaining the EGR tube
to the EGR valve and remove the EGR tube.
(4) Remove the two bolts retaining the EGR valve
to the intake manifold elbow and remove EGR valve.
(5) Discard both of the old EGR mounting gaskets.
INSTALLATION
(1) Clean the intake manifold of any old gasket
material.
(2) Clean the end of EGR tube of any old gasket
material.
(3) Position the EGR valve and new gasket to the
intake manifold elbow.
(4) Install two EGR valve mounting bolts. Do not
tighten bolts at this time.
(5) Position new gasket between EGR valve and
EGR tube.
(6) Install two EGR tube bolts. Tighten all four
mounting bolts to 23 N·m (204 in. lbs.).
(7) Tighten EGR tube fitting at exhaust manifold.
(8) Connect vacuum line to EGR valve.
EGR TUBE
The EGR tube connects the EGR valve to the rear
of the exhaust manifold.
REMOVAL
(1) Remove two EGR tube mounting bolts at EGR
valve end of tube.
(2) Loosen fitting at exhaust manifold end of tube.
(3) Remove EGR tube and discard old gasket.
(4) Clean gasket mating surfaces and EGR tube
flange gasket surfaces.
(5) Check for signs of leakage or cracked surfaces
at both ends of tube, exhaust manifold and EGR
valve.
INSTALLATION
(1) Install a new gasket to EGR valve end of EGR
tube.
(2) Position EGR tube to engine.
(3) Loosely tighten fitting at exhaust manifold end
of tube.
(4) Install 2 mounting bolts at EGR valve end of
tube. Tighten bolts to 23 N·m (204 in. lbs.) torque.
(5) Tighten fitting at exhaust manifold end of tube.
Fig. 2 Internal Vacuum Pump
1 – INTERNAL VACUUM PUMP AND DRIVE GEAR
XJ
EMISSION CONTROL SYSTEM
25 - 7
DESCRIPTION AND OPERATION (Continued)
2000 JEEP CHEROKEE
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