EMISSION CONTROL SYSTEMS
TABLE OF CONTENTS
page
page
ON-BOARD DIAGNOSTICS . . . . . . . . . . . . . . . . . . . 1
EVAPORATIVE EMISSION CONTROLS . . . . . . . . . 22
EXHAUST GAS RECIRCULATION (EGR)
SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
ON-BOARD DIAGNOSTICS
TABLE OF CONTENTS
page
page
DESCRIPTION AND OPERATION
SYSTEM DESCRIPTION . . . . . . . . . . . . . . . . . . . . 1
MALFUNCTION INDICATOR LAMP (MIL) . . . . . . . . 2
DRB III STATE DISPLAY TEST MODE . . . . . . . . . . 2
DRB III CIRCUIT ACTUATION TEST MODE . . . . . . 2
DIAGNOSTIC TROUBLE CODES . . . . . . . . . . . . . . 2
DIAGNOSTIC TROUBLE CODE
DESCRIPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 3
MONITORED SYSTEMS. . . . . . . . . . . . . . . . . . . . 12
TRIP DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . 16
MONITORED COMPONENT . . . . . . . . . . . . . . . . . 16
NON-MONITORED CIRCUITS . . . . . . . . . . . . . . . 20
HIGH AND LOW LIMITS . . . . . . . . . . . . . . . . . . . . 21
SPECIFICATIONS
LOAD VALUE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
DESCRIPTION AND OPERATION
SYSTEM DESCRIPTION
DESCRIPTION
OBD II requires that vehicles falling under OBD II
guidelines utilize the following system monitors:
•
Comprehensive Component Monitor (inputs/out-
puts for powertrain management that affect emis-
sions, but do not have a specific major monitor)
•
Fuel
Control
Monitor
(fuel
compensation
required to maintain stoichiometric ratio rich/lean)
•
Misfire Monitor (change in crankshaft speed)
•
Oxygen Sensor Heater Monitor (response and
performance of oxygen sensors)
•
Catalyst Monitor (Performance and efficiency of
catalyst)
•
Evaporative Emissions Monitor (performance of
and leaks from EVAP system)
•
Exhaust Gas Recirculation Monitor (flow perfor-
mance of EGR system)
The software was rewritten to enable the PCM to
carry out the responsibilities to meet these required
guidelines. The PCM now contains a Task Manager.
OPERATION
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
output circuit shorts to ground when engine operates
above 2400 RPM (resulting in 0 volt input to the
NS
EMISSION CONTROL SYSTEMS
25 - 1
