Circuit Description

Heated Oxygen Sensor-1 (HO2S-1) heater reduces time required to enter closed loop operation, and allows accurate catalyst monitoring by maintaining a sufficiently high temperature. DTC will set when:

• HO2S-1 heater is operating and heater current exceeds 2 amps.
• HO2S-1 heater is operating and heater current is .2 amp or less.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will turn HO2S-1 heater off.