Circuit Description

Heated Oxygen Sensors (HO2S) decreases amount of time required to enter closed-loop operation where maximum fuel efficiency is attained. ECM diagnoses heater and related circuit by monitoring electrical current. ECM will set this DTC when no signal is being received.

DTC will set when:

• HO2S heater voltage is fixed between 2.34 and 3.6 volts.
• Battery voltage not between 11-16 volts.
• Engine running.