Circuit Description

When ignition is turned on, battery voltage is supplied to HO2S heater to provide for faster sensor warm-up, thus 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 CKP, ECT, EGR pintle position, IAT, MAF, MAP or TP sensor DTCs set.
• No EVAP system DTC set.
• No fuel injector circuit, fuel trim or misfire DTCs set.
• ECT and IAT less than 95°F (35°C) at start-up.
• Difference between ECT and IAT is within 11°F (6°C) of each other.
• HO2S 2 voltage remains within 150 mV of bias voltage (about 450 mV) for longer amount of time than it should.