Circuit Description

PCM reads Heated Oxygen Sensor (HO2S) activity for 100 seconds. During this period, PCM counts the number of Lean/Rich (L/R) and Rich/Lean (R/L) switches.

With this information, an average time for all transitions can be determined. PCM then divides R/L average by L/R rich average to obtain a ratio. If HO2S ratio is not within range, DTC P1134 will set.

Conditions for setting DTC:

• No ECT, IAT, MAF, MAP, or TP sensor DTCs set.
• No fuel trim, injector or HO2S 1 heater circuit DTCs set.
• No EGR or EVAP system DTCs set.
• Engine speed 1000-3000 RPM.
• Engine operating in closed loop mode.
• Conditions present during 100 second monitoring period.
• Ratio of average response times not 0.4-5.0.