Emission Control Systems - Chrysler 1998 Voyager Service Manual

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EVAPORATIVE EMISSION CONTROLS . . . . . . . . 13
EXHAUST GAS RECIRCULATION (EGR)
SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
GENERAL INFORMATION
SYSTEM DESCRIPTION . . . . . . . . . . . . . . . . . . . 1
DESCRIPTION AND OPERATION
CIRCUIT ACTUATION TEST MODE . . . . . . . . . . . 3
COMPONENT MONITORS . . . . . . . . . . . . . . . . . 10
DIAGNOSTIC TROUBLE CODES . . . . . . . . . . . . . 3
HIGH AND LOW LIMITS . . . . . . . . . . . . . . . . . . . 11
GENERAL INFORMATION
SYSTEM DESCRIPTION
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 Malfunction Indicator Lamp in this
section.
Certain criteria must be met before the PCM
stores a DTC in memory. The criteria may be a spe-
cific 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

EMISSION CONTROL SYSTEMS

CONTENTS
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ON-BOARD DIAGNOSTICS
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EMISSION CONTROL SYSTEMS
ON-BOARD DIAGNOSTICS . . . . . . . . . . . . . . . . . . 1
INDEX
LOAD VALUE . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
MALFUNCTION INDICATOR LAMP (MIL) . . . . . . . 1
MONITORED SYSTEMS . . . . . . . . . . . . . . . . . . . . 8
NON-MONITORED CIRCUITS . . . . . . . . . . . . . . . 11
STATE DISPLAY TEST MODE . . . . . . . . . . . . . . . 2
TRIP DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . 10
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 Moni-
tored Systems, Components, and Non-Monitored Cir-
cuits in this section.
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 DRB scan tool to
erase all DTC's and extinguish the MIL.
Technicians can display stored DTC's by using the
DRB scan tool. Refer to Diagnostic Trouble Codes in
this section. For DTC information, refer to charts in
this section.
DESCRIPTION AND OPERATION
MALFUNCTION INDICATOR LAMP (MIL)
As a functional test, the Malfunction Indicator
Lamp (MIL) illuminates at key-on before engine
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