Firebird V8-5.7L VIN G (2001)
Typical Drive Cycle
Following a DTC info clear, System Status will clear for one or all of these systems. Following a battery disconnect or a PCM replacement, all System
Status information will clear.
Three-Way Catalyst Oxygen Storage Capacity
The PCM must monitor the Three-Way Catalyst system (TWC) for efficiency. In order to accomplish this the PCM monitors the pre-catalyst and
post-catalyst oxygen sensors. When the TWC is operating properly, the post-catalyst (2) oxygen sensor will have significantly less activity than the
pre-catalyst (1) oxygen sensor. The TWC stores oxygen during its normal reduction and oxidation process. The TWC releases oxygen during its normal
reduction and oxidation process. The PCM calculates the oxygen storage capacity using the difference between the pre-catalyst and post-catalyst oxygen
sensor's voltage levels.
Whenever the sensor activity of the post-catalyst oxygen sensor (2) nears the sensor activity of the pre-catalyst oxygen sensor (1), the catalyst's efficiency
is degraded.
Aftermarket HO2S characteristics may be different from the original equipment manufacturer sensor. This condition can lead to a false pass or to a false
fail of the catalyst monitor diagnostic. If an aftermarket catalyst does not contain the same amount of precious metal content as the original part, the
correlation between the oxygen storage and the conversion efficiency may be altered enough to set a false DTC.
Torque Management
Torque management is a function of the PCM that reduces engine power during certain conditions. Torque management is performed for the following
reasons:
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In order to prevent over stressing the powertrain components
^
In order to prevent damage to the vehicle during certain abusive maneuvers
^
In order to reduce the engine speed when the IAC is out of the normal operating range
The PCM monitors the following sensors and engine parameters in order to calculate the engine output torque:
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The Air/Fuel ratio
^
The mass air flow
^
The manifold absolute pressure
^
The intake air temperature
^
The spark advance
^
The engine speed
^
The engine coolant temperature
^
The A/C clutch status
