HO2S Sensor 1

The scan tool displays NOT READY or READY. This indicates the status of the fuel control exhaust oxygen sensor. The scan tool indicates that the exhaust oxygen sensors are ready when the PCM detects a fluctuating HO2S voltage sufficient to allow closed loop operation. This does not occur unless the exhaust oxygen sensors are warmed up.

The scan tool range is 0 to 1132 mV. This represents the fuel control exhaust oxygen sensor output voltage. The reading should fluctuate constantly within a range of 10 mV (lean exhaust) to 1000 mV (rich exhaust) while operating in Closed Loop.