K Yukon/Denali 4WD V8-5.7L VIN R (2000)
Catalytic Converter: Description and Operation
Three Way Catalyst (TWC) Oxygen Storage Capacity
The control module monitors the post catalyst HO2S signal voltage in order to measure the oxygen storage capacity of the converter. A good catalytic
converter is indicated when the post-catalyst HO2S signal voltage is relatively steady (2) compared to the pre-catalyst HO2S signal voltage (1).
A malfunctioning catalytic converter is indicated when the post-catalyst HO2S signal voltage is more active (2), similar to the pre-catalyst HO2S signal
voltage (1).
In addition to catalyst monitoring, the post catalyst HO2S has a limited role in fuel control.
IMPORTANT: Do not use post-catalyst HO2S voltage activity in order to determine the efficiency of the TWC converter unless directed to do so by a
diagnostic procedure.
The catalyst monitor on-board diagnostic tests can be effected by the following:
^
A slightly degraded or marginal catalyst
^
Fuel containing high amounts of the following contaminants:
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Sulfur
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Silica
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Lead
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Phosphorus
^
Exhaust system leaks may cause the following:
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Prevent a degraded or marginal TWC converter from failing a diagnostic test
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Cause a normally functioning TWC converter to fail a diagnostic test
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Prevent the diagnostic test from running
^
An aftermarket HO2S
^
An aftermarket catalytic converter
