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.
Checking output signals from HO2S under detecting condition, if an output signal is above 1.08V for more than predeterminate time, ECM sets P0158.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Signal check, high |
•
Poor connection
•
Short to battery in harness
•
HO2S(B2/S2) |
Enable Conditions |
•
Battery voltage > 10.7V
•
Exhaust gas temperature (model) < 900C
•
After enough heated | |
Threshold value |
•
B1S1 sensor voltage > 1.08V | |
Diagnosis Time |
•
10 sec | |
MIL On Condition |
•
2 Driving Cycles |
Fig. 1) Normal waveforms of front HO2S(the upper) and rear HO2S(the lower)
After warming-up, if accelerator pedal is released suddenly around 4000rpm, 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.
