Liberty 2WD V6-3.7L VIN K (2003)
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.
Downstream Sensors - 3.7L Engine: 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.
