RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
The downstream oxygen sensor also provides an input to determine catalytic convertor efficiency.
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Upstream Sensors - California Emissions Package : Two upstream sensors are used (1/1 and 2/1). The 1/1 sensor is the first sensor to
receive exhaust gases from the #1 cylinder. They provide an input voltage to the PCM. The input tells the PCM the oxygen content of the
exhaust gas. The PCM uses this information to fine tune fuel delivery to maintain the correct oxygen content at the downstream oxygen sensors
. The PCM will change the air/fuel ratio until the upstream sensors input a voltage that the PCM has determined will make the downstream
sensors output (oxygen content) correct.
The upstream oxygen sensors also provide an input to determine mini-catalyst efficiency. Main catalytic convertor efficiency is not calculated
with this package.
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Downstream Sensors - California Emissions Package : Two downstream sensors are used (1/2 and 2/2). The downstream sensors are used
to determine the correct air-fuel ratio. As the oxygen content changes at the downstream sensor, the PCM calculates how much air-fuel ratio
change is required. The PCM then looks at the upstream oxygen sensor voltage, and changes fuel delivery until the upstream sensor voltage
changes enough to correct the downstream sensor voltage (oxygen content).
The downstream oxygen sensors also provide an input to determine mini-catalyst efficiency. Main catalytic convertor efficiency is not
calculated with this package.
Engines equipped with either a downstream sensor(s), or a post-catalytic sensor, will monitor catalytic convertor efficiency. If efficiency is
below emission standards, the Malfunction Indicator Lamp (MIL) will be illuminated and a Diagnostic Trouble Code (DTC) will be set.
Refer to Monitored Systems in Emission Control Systems for additional information.
