Circuit Description

WARNING: This page is about a different car, the 2000 Isuzu Hombre. However, it is still accessible from the selected car via links, so may be relevant.

Vehicle Control Module (VCM) provides about 0.45-volt reference to HO2S high and low circuits. HO2S sensor signal voltage varies from about one volt when exhaust is rich to about 0.1 volt when exhaust is lean. VCM reads and stores sensor voltage information and evaluates the voltage samples to determine amount of time sensor voltage is out of range. If HO2S voltage is out of predetermined range, DTC will set.

Conditions required to set DTC are:

No ECT, IAT, MAF, MAP or TP sensor DTCs set.
No EVAP system DTC set.
No other DTC tests in progress.
No device controls active.
HO2S average transition tome from lean-to-rich or rich-to-lean is greater than 125 milliseconds.