Circuit Description

Heated Oxygen Sensor (HO2S) 1 refers to bank 1 sensor 1. 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 counts number of times a rich-to-lean and lean-to-rich response is indicated and adds amount of time it takes to complete all transitions. PCM uses this information to determine average time for each transition. If average response time is slow, DTC P0133 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 in closed loop fuel control mode for at least 2 minutes.
• Engine speed 1000-3000 RPM.
• ECT greater than 122°F (50°C).
• MAF 15-29 grams per second (A/T).
• MAF 10-30 grams per second (M/T).
• Lean-to-rich or rich-to-lean average transition response time greater than 90 milliseconds.