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 an output signal is below 0.06V for more than predeterminate time, PCM sets P0157.
DTC Detecting Condition
Item | Detecting Condition | Possible Cause |
DTC Strategy | Signal check, low
| Poor connection Short to ground in harness B2/S2 |
Case1 | Enable Conditions | Short term FT < 1.25 (upper limit)
Battery voltage > 10.7V
Exhaust gas temperature (model) < 900C
After enough heated
|
Diagnostic Time | 40 sec
|
Case2 | Enable Conditions | ECT < 40C
ECT at the end of last trip > 60C
Time after engine start < 1.0 sec
|
Diagnostic Time | 0.1 sec
|
Threshold Value | Sensor voltage < 0.06V
|
MIL ON Condition | 2 driving cycle
|
Diagnostic Circuit Diagram
Signal Waveform & Data
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.