Circuit Description
WARNING: This page is about a different car, the 2003 Toyota 4Runner. However, it is still accessible from the selected car via links, so may be relevant.
Heated Oxygen Sensor (HO2S) monitors exhaust gas oxygen content and delivers input signals to ECM. HO2S (Bank 1 & 2, Sensor 1) are located in exhaust system in front of catalytic converter. HO2S (Bank 1 & 2, Sensor 2) are located in exhaust system after catalytic converter. ECM uses input signals to determine fuel injection system operation. The ECM provides a pulse width modulated control circuit to adjust current through heater. The HO2S heater circuit uses the EFI relay on the B+ side of circuit.
DTCs is set when:
- For P0031, P0037, P0051 & P0057 - HO2S heater current is 0.25 amp or less when heater operates with 10.5-11.5 volts (one trip detection logic).
- For P0032, P0038, P0052 & P0058 - Oxygen sensor heater current draw exceeds 2 amps (one trip detection logic).
- Oxygen sensor heater circuit is open or shorted.
- Defective Oxygen sensor heater.
- Defective EFI relay.
- Defective ECM.