General Information

Component Location





General Description

The rear heated oxygen sensor is mounted on the rear side of the Catalytic Converter (warm-up catalytic converter) or in the rear exhaust pipe, which is able to detect catalyst efficiency. The rear heated oxygen sensor (HO2S) produces a voltage between 0V and 1V. This rear heated oxygen sensor is used to estimate the oxygen storage capability. If a catalyst has good conversion properties, the oxygen fluctuations are smoothed by the oxygen storage capacity of the catalyst. If the conversion provided by the catalyst is low due to aging, poisoning or misfiring, then the oxygen fluctuations are similar to signals from the front oxygen sensor.

DTC Description

Checking output signals from HO2S under detecting condition, if HO2S's signal is rich during fuel cut-off conditions, ECM sets P2273. MIL (Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycles.

DTC Detecting Condition





Specification





**In case of open circuit, voltage is set to 0.45V (Pumping current OFF) or 3.5V (Pumping current ON)

Diagnostic Circuit Diagram





Signal Waveform & Data








Fig.1) Normal waveforms of front HO2S (the upper) and rear HO2S (the lower)
Fig.2) Normal graph of front HO2S and rear HO2S at idle.

After warming-up, if accelerator pedal is released suddenly around 4000 rpm, the HO2S signal reading will be lower than 200mV resulting from Fuel cut-off for the moment. Conversely, if suddenly accelerator pedal is depressed, HO2S signal reading will be around 0.6V ~ 1.0V. At idle, Normally HO2S signal will switch from lean to rich with 3 Hz. And as racing, Its frequency rises.