Circuit Description

Heated Oxygen Sensor (HO2S) decreases amount of time required for system to enter closed-loop operation. ECM diagnoses the heater and its related circuit by continuously monitoring electrical current. ECM will set DTC if oxygen sensor does not become active within 20 seconds after heater temperature reaches 99°F (37°C). DTC will also set when battery voltage is not between 11.03-15.52 volts.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. ECM will record operating conditions at time of failure and store information in freeze frame buffer.