Circuit Description
WARNING: This page is about a different car, the 2003 Toyota Camry. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
- Detecting condition for DTCs P0037 and P0043 is when heater current is 0.2 A or less when the heater operates (1 trip detection logic).
- Detecting condition for DTCs P0038 and P0044 is when heater current exceeds 2 A when the heater operates (1 trip detection logic).
For circuit description of heated oxygen sensor No. 2, see DTC P0136, DTC P0137 & DTC P0138 . For circuit description of heated oxygen sensor No. 3, see DTC P0142: OXYGEN SENSOR CIRCUIT MALFUNCTION (BANK NO. 1 SENSOR NO. 3) .
The engine control module (ECM) provides a pulse width modulated control circuit to adjust current through the heater. The heated oxygen sensor heater circuit uses a relay on the B+ side of the circuit. See Fig 1.