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 the 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.
PCM sets DTC P0137 if the PCM detects that Signal Voltage lower than the possible range of a properly operating rear HO2S.
ITEM | DETECTING CONDITION | POSSIBL ECAUSE |
DTC Strategy | ●Check short circuit to ground on rear HO2S | ● Short to ground in signal harness ● Contact resistance in connectors ● Faulty Heated O2 Sensor(HO2S) |
Enable Condition | ● Catalyst temperature model ＞ 400°C(752°F) ● No relevant failure ● 10 ＜ Battery voltage ＜ 16 ● Closed loop mode ● Lambda controller is not on the limit ● Catalyst purge after fuel cut off is not active | |
Threshold Value | ● Downstream O2 Sensor voltage ＜ 0.02V & sensor element resistance ＜ 30Ω | |
Diagnostic Time | ● 20 sec. |
