Circuit Description

PCM provides about 0.45 volt reference to HO2S 1. HO2S 1 sensor signal voltage varies from about one volt when exhaust is rich to about 0.1 volt when exhaust is lean. PCM reads and stores sensor voltage information and evaluates the voltage samples to determine amount of time sensor voltage is out of range. If HO2S 1 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 fuel injector circuit, fuel trim, misfire or transaxle DTCs set.
• Engine running for at least 4 minutes.
• HO2S 1 signal voltage signal voltage stays 0.4-0.5 volt for greater than 30 seconds.