Circuit Description

When ignition is turned on, battery voltage is supplied to HO2S heater to provide for faster sensor warm-up, allowing sensor to become active in a shorter period of time. PCM reads amount of time necessary for sensor to become active after start-up.

Conditions required to set DTC are:

• No related DTCs set.
• ECT and IAT less than 90°F (32°C) at start-up.
• Difference between ECT and IAT no greater than 9°F (5°C).
• Ignition is 11-16.6 volts.
• Throttle angle is less than 40 percent.
• MAF calculated airflow is less than 18 grams per second.
• HO2S-2 reading remains within .15 volt of bias reading (.4-.5 volt) for longer amount of time than it should.