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 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.
DTC Description
P0130/P0136: If circuit voltage is higher than 4.5V after 5V is applied to the HO2S output line via a resistor, the ECM judged as a open circuit and DTC is set.
DTC Detecting Condition
Item | Detecting Condition | Possible cause |
Monitoring Strategy | ? Rationality check | ? Open HO2S ? Short HO2S ? Faulty HO2S ? Faulty ECM ? Poor connections between HO2S and ECM ? Misplaced,bent,loose or corroded terminals. |
Threshold value | ? Counter of ushk > 1.25V during 0.05sec after heater on-> off : > 5 times |
Enable Conditions | ? No signal check high error ? Heater on->off counter > 10 times |
Diagnostic Time | |
Fail Safe | ? None |
Specification
HO2S | Normal Parameter(at 2000 rpm after warming up) |
Signal Voltage | 500 ~ 1000 Mv |
Schematic Diagram
Signal Waveform
This figures show the wave form measured at terminal 2 of HO2S at idle RPM.
The average voltage of HO2S should be 0.5 V.
When sudden decceleration,the voltage at point ? should be below 0.2V.
The switching time marked ? from lean to rich should be within 200ms,if longer than 200ms HO2S may be not good.
The switching time marked ? from rich to lean should be within 300ms,if longer than 300ms HO2S may be not good.
In case the average voltage of HO2S is over 0.6V.
Possible cause:Injector leakage,faulty Pressure regurator Faulty MAPS,ECTS. |
The rear oxygen sensor output is usually not changeable like front oxygen sensor,however,if it moves like front oxygen sensor,the catalytic converter is broken.