Circuit Description

PCM provides a .45 volt reference signal to the HO2S through the Bank 2 high signal circuit. When HO2S reaches operating temperature, it will generate a counter voltage that will vary based on the amount of oxygen in the exhaust. A lean exhaust will generate a low voltage and cause the reference voltage (.45 volt) to drop lower. A rich exhaust will generate a high voltage and cause the reference voltage to increase. If sensor cannot respond under the test conditions and generate a voltage greater than .61 volt or less than .31 volt, DTC will set.

Conditions for setting DTC:

• DTCs P0117, P0118, P0121, P0122 and P0123 not set.
• TP sensor 1.0-81.6 degrees.
• Coolant temperature at 163°F (72.5°C) or greater.
• Calculated throttle position switch open.
• Engine speed at 800 RPM or greater.