The catalyst’s efficiency is demonstrated by its ability to oxidize CO and hydrocarbon emissions. The Powertrain Control Module (ECM) compares the output signals of the front and rear oxygen sensors to determine whether the output of the rear sensor is beginning to match the output of the front oxygen sensor. Air/fuel mixture compensation keeps the frequency of the front oxygen sensor high due to the changes from rich-to-lean combusition. The catalyst causes the rear oxygen sensor to have a lower frequency. As the catalyst wears, the rear oxygen sensor’s signal trace begins to match the front oxygen sensor’s signal trace. That is because the catalyst becomes saturated with oxygen and cannot use the oxygen to convert hydrocarbon and CO into H2O and CO2 with the same efficiency as when it was new. A completely worn catalyst shows a 100% match between the frequency of the front and rear sensors.
If the S1 signal is advanced compared to the S2 controller value, P2096 is stored.
Item
Detecting Condition
Possible Cause
DTC Strategy
O2 sensor characteristic line shift
Catalyst converter
S1
ECM
Enable Conditions
Dew point end detected
Target lambda = 1
Battery voltage > 10.7V
Exhaust gas temperature (model) : 600? ~ 800?
No upstream O2 sensor error or downstream O2 sensor ready
Engine speed 1000~3800rpm
Engine load 15~78.8%
Threshold Value
The second controller by S2 >1sec
Diagnostic Time
15 sec
MIL ON Condition
3 driving cycle
? S1 : upstream oxygen sensor / S2 : downstream oxygen sensor
If you release the accelerator pedal suddenly after engine running about 4000 rpm, fuel supply will stop for short period and the O2 sensor service data in the GDS will display values 200mV or lower. When you suddenly press on the accelerator pedal down, the voltage will reach 0.6 ~ 1.0 V. When you let the engine idle again, the voltage will fluctuate between 200 mV or lower and 0.6 ~ 1.0 V. In this case, the O2sensor can be determined as good.