Circuit Description

Heated oxygen sensors are used to minimize the amount of time required for "closed loop" fuel control operation and to allow accurate catalyst monitoring. The oxygen sensor heater greatly decreases the amount of time required for fuel control sensors Bank 1 HO2S1 and Bank 2 HO2S1 to become active. Oxygen sensor heaters are required by post-catalyst monitor sensors to maintain a sufficiently high temperature which allows accurate exhaust oxygen content readings further from the engine.

The Engine Control Module (ECM) starts to monitor the Bank 1 HO2S1 current after engine running continuously. If ECM detects that the HO2S1 heater current is below the specified value for the predetermined time, DTC P0135 will be set.