Operation CHARM: Car repair manuals for everyone.

General Information





Component Location





General Description

The normal operating temperature of the HO2S (Heated Oxygen Sensor) ranges from 350 to 850°C (662 to 1562°F). The HO2S heater greatly decreases the amount of time required for fuel control to become active. The ECM provides a pulse width modulated control circuit to adjust current through the heater. When the HO2S is cold, the value of the resistance is low and the current in the circuit is high. On the contrary, if the temperature in the resistor of the sensor rises, the current drops gradually.

DTC Description

When ECM detects short to power in the heater control circuit (B1S1), ECM sets DTC P0032.

DTC Detecting Condition





Specification





Diagnostic Circuit Diagram





Signal Waveform & Data




Fig.1) The signal waveforms of front HO2S (the lower) and heater (the upper) at idle
The output voltage of the upstream HO2S changes continuously based on the air/fuel ratio. The ECM changes the air/fuel mixture based on the HO2S values. Because the sensor must be hot to operate properly, a heater unit is installer in the HO2S for a quicker warm up and to maintain the sensor temperature. The main relay supplies B+ to the heater circuit while the ECM controls the ground side. The ECM pulses the ground to control the current flow through the heater circuit.