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 every 10 sec. under detecting condition, if an output signal indicating open in the circuit lasts for more than 6.3 sec. PCM sets P0160. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item
Detecting Condition
Possible cause
DTC Strategy
? Open
? Poor connection
? Open in harness
? HO2S(B2/S2)
? PCM
Enable Conditions
? No sensor cooled status
? The minimum airflow = 2g/s
? The battery voltage = 10V
? Engine running state >60 sec.
? Coolant temperature = 60°C(140°F)
? No fuel reduction
? No transient condition
? No fuel-out state
? No disabling fault
Threshold value
Case 1
? At pumping current ON
? 1.2V = Voltage of HO2S = 3.9V
Case 2
? At pumping current OFF
? 0.415V = Voltage of HO2S = 0.515V
Diagnosis Time
? Continuous (More than 6.3 sec.failure for every 10 sec.test)
MIL On Condition
? 2 Driving Cycles
Air/fuel mixture
Voltage(V)
Rich
0.75 ~ 1V
Lean
0 ~ 0.12V